About Solar Electricity

Solar electricity systems – also known as photovoltaics, or PV for short - use free renewable energy from the sun and convert this into electricity. This electricity can then be used in the home and the excess exported to the national grid. Installation of solar electricity systems also gives access to additional income through the government’s Feed in Tariff scheme.

We recommend that before installing energy generation technologies such as solar electricity you improve the energy efficiency of your property as far as is practically possible.

Please refer to the Energy Efficiency results for your property, the About Energy Efficiency tab and the Help with Installation page for more information on how to improve your property’s energy efficiency.

For further information about solar electricity and the results given by the Energy Calculator please choose from the following questions:

What can I do next to get solar electricity panels installed?

For information on local schemes which can provide support for installation and financial support available please visit the Help with Installation page.

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What are these results based on?

The results given by the Energy Calculator are based on data about properties within Nottingham. The data has not been collected in an intrusive way – it is based on information we can gain from maps.

Where we don’t have all the necessary information on the ‘real’ state of a property we have made assumptions based on information about similar properties. We have tried hard to make the data we use as accurate as possible and are confident that the Energy Calculator will provide you with useful results.

Please note though that the results that the Energy Calculator gives should be regarded as indicative and that all values should be verified by a qualified professional before installation of any measures takes place.

You can help us improve the Energy Calculator by telling us more about your property in our Survey.

The Energy Calculator also uses information on government schemes such as Feed in Tariffs as well as data on energy prices in the modelling of financial savings and paybacks.

A number of tools exist on the website of the Nottingham Energy Partnership which allow you to carry out your own solar assessment, in which you can input values relating to your property and desired solar system yourself.

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The Energy Calculator says that my home may not be suitable for solar electricity – why is this?

There are two reasons why this may be the case:

  • Your property is modelled as having a north-facing roof or otherwise as receiving solar radiation of less than 815kWh/m2/year (kilowatt hours per square metre per year). This is considered to not be enough to make installation of a solar electricity system worthwhile.
  • Your property is a flat and therefore does not have its ‘own’ roof on which to put solar electricity panels. This does not necessarily mean that it is not possible to put solar electricity panels on the roof, but that the ownership of the roof and the sharing of electricity and income generated by an installed system would need to be considered. If you have a shared roof and are interested in investigating the potential for a solar electricity system then please see our Help with Installation page for sources of support with this.

We are working to improve the Energy Calculator with the aim that in future it will be possible to see solar electricity results for shared roofs.

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How is the sun’s energy converted into electricity?

The sun’s energy is captured using photovoltaic (PV) cells. Each cell is made from one or two layers of semiconducting material, usually silicon. When light shines on the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is produced.

The power generated by a solar electricity system is measured in kilowatts peak (kWp). This is the amount of energy the photovoltaic cells generate in full sunlight and standardised conditions.

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How is the Energy Generated figure calculated?

The calculation of the amount of energy which would be generated per year by the solar electricity system suggested is based on modelling of the amount of solar energy (radiation) which your property receives and the System Size, which is calculated based on an assumption about the area of your roof which is suitable for solar panels.

The modelling of solar radiation takes into account a number of factors including the orientation of the roof (i.e. does it face south or east etc) and its slope.

Shading is important to the electricity output of the solar panels and this is built into the modelling using an assumption about average level of shading in Nottingham. However if your roof is subject to a large amount of shading – for example from chimneys, trees, or neighbouring properties – then the amount of energy which solar panels would be able to produce may be lower than that suggested by the Energy Calculator.

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How is System Size calculated?

System Size is calculated using data on the total size of your roof and an assumption about the area of your roof which is suitable for solar panels.

Other factors such as skylights and vents have not been incorporated into our model. If these are present they may reduce the amount of solar panels your roof could accommodate.

The unit used to describe system size is kilowatt peak (kWp). This is the amount of energy the cell generates in full sunlight. Each kilowatt peak requires around 8m2 of available roof area.

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What is a kilowatt hour (kWh)?

The kilowatt hour is a unit of energy which integrates the amount of power used (in kilowatts) and the time it is used for (in hours). It is used to measure the amount of energy used in homes. You may be familiar with this as it will appear on your electricity and gas bills.

For example:

  • An electric heater rated at 1 kilowatt (1000 watts), operating for one hour uses one kilowatt hour of energy.
  • Using a 15 watt light bulb for one hour consumes 0.015 kilowatt hours of electricity.
  • Using a 15 watt light bulb for one hundred hours consumes 1.5 kilowatt hours of electricity.

It is also used as a measure of electricity generated. So for example a 1kWp (kilowatt peak) solar panel generating at full capacity for one hour would produce 1 kilowatt hour of electricity. This could be used to power the 1 kilowatt heater for one hour.

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What is kWh/year?

kWh/year means 'kilowatt hours per year'. This is the number of kilowatt hours used (or generated) annually.

So, for example, if a 1 kW heater is used for one hour per day for 365 days of the year it will use 365 kilowatt hours over the year (1kW x 1 hour x 365 days).

If a 1kWp solar panel generates electricity at full capacity for 2 hours per day for one year, it will generate 730 kilowatt hours over the year (1kW x 2 hours x 365 days).

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Will the amount of electricity that my solar panels generate vary at different times of the year?

The strength of the solar energy (radiation) available depends on factors including the time of year and the time of day. The amount of energy generated can be further affected by the amount of dust and water vapour in the air, the amount of cloud cover and any shading of the solar panels.

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Is it possible to generate electricity on cloudy days?

Yes, electricity will be generated on cloudy days, although at a lesser rate than on days with full sun. The important thing to bear in mind is that solar power depends on the intensity of radiation, not necessarily direct sunlight. The PV (solar electricity) cells will take in direct sunlight and diffuse sunlight (sunlight which has travelled through cloud).

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How does the generated electricity fit with my national grid electricity supply?

The solar electricity (PV) system automatically supplies you with electricity via an inverter during daylight hours. At night or when your electricity demand is higher than your PV system’s output, you will automatically receive electricity from the National Grid (in addition to the PV supply) without any interruption to your supply.

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How does the generated electricity fit with my national grid electricity supply?

The solar electricity (PV) system automatically supplies you with electricity via an inverter during daylight hours. At night or when your electricity demand is higher than your PV system’s output, you will automatically receive electricity from the National Grid (in addition to the PV supply) without any interruption to your supply.

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What if I produce more electricity than I use?

If you produce more electricity than you use (for example on a sunny day when you are not at home) then the excess will be exported to the grid. Under the Feed-In Tariff scheme you will receive both an export payment for electricity exported to the grid and an additional generation payment for all power you generate (whether you use it yourself or export it to the grid).

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How is Installation Cost calculated?

Installation costs for solar electricity are based on the assumption that each 1kWp (kilowatt peak) of generation capacity will cost £3,500 to install. This is based on knowledge of average installation costs in Nottingham. However if you receive quotes from installers they may vary from this. See our Help with Installation page for links to installers.

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How are first year savings calculated?

This is an estimate of the savings you could make in the first year. It includes income from the Feed-In Tariff scheme both for generation of electricity and the export of some of it to the grid, and savings made on your electricity bill as a result of generating some of the electricity that you use yourself.

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How is Payback period calculated?

The payback period is the length of time that it will take for the financial savings (including Feed in Tariff income) that result from the solar electricity system to pay back the installation cost. The period is calculated using the installation cost and the First Year Savings figure, with inflation rates applied to the latter to capture Retail Price Index-linked increases in Feed in Tariff income (modelled at 3% per year) and assumed increases in electricity bills (modelled at 6% per year) over time.

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What are Feed-In Tariffs?

The Feed In Tariffs scheme has been introduced by the government to improve financial incentives for householders to install renewable electricity technologies such as solar electricity (PV) systems.

The scheme guarantees a minimum payment for all electricity generated by the system, as well as a separate payment for any electricity exported to the grid. These payments are made to you by your energy supplier.

The Tariffs give three financial benefits:

  • A payment for all the electricity you generate, even if you use it yourself
  • Additional payments for electricity you export to the grid. At present this payment is based on the assumption that 50% of the electricity that you generate is exported
  • A reduction on your standard electricity bill, due to you using electricity you produce yourself

The Tariff paid for electricity generated by systems with a size of less than 4kWp (kilowatts peak) is 21.0p per kWh (kilowatt hour). The Tariff paid for export to the grid is 3.1p per kWh. These rates have been used in calculating First Year Savings and Payback periods. These payments are guaranteed for 25 years and are RPI-linked so that they will rise with inflation.

Please note that the above generation tariff of 21.0p per kWh came into effect on April 2012. This reduction will help ensure that current tariff levels for solar PV are more closely matched to installation costs.

In order to ensure that solar PV is considered as part of a whole-house approach to saving energy and carbon, the government has also introduced a minimum energy efficiency requirement for properties claiming the tariff for solar PV. From 1st April properties will be required to produce an Energy Performance Certificate rating of ‘D’ or above to qualify for the full FIT rates. Where properties do not meet the requirement, they will receive a tariff of 9p/kWh.

Please see the Energy Efficiency results for your property and refer to the Help with Installation page for support on installing energy efficiency measures.

See the Energy Saving Trust website for more details on Feed in Tariffs.

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How are Annual CO2 (carbon dioxide) savings calculated?

Each 1kWp (kilowatt peak) of installed generation capacity will produce around 700-800kWh (kilowatt hours) of electricity per year, varying dependent on the amount of solar radiation the property receives.

A conversion factor is used to calculate how much carbon dioxide will be saved by replacing electricity imported from the grid with zero carbon electricity generated by solar panels. A 1kWp system will save around 400kg of carbon dioxide per year.

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Do I need planning permission to install solar panels?

Domestic solar electricity systems are classed as ‘permitted development’ and therefore do not usually require planning permission, although you are advised to check in each instance with the Council.

The installer will need to be recognised as competent to assess any structural issues - such as those relating to installation of roof-mounted renewable energy systems - through being accredited under a recognised scheme. You should therefore check with an installer that they are accredited under such a scheme (and if you are unsure contact Building Control). If the installer is not accredited then you will need to notify Building Control of the works.

Installers of solar panels should also be registered under the Microgeneration Certification Scheme (MCS). We recommend that in all cases you use MCS certified installers. If the installer is not MCS accredited then you will need to notify Building Control of the works.

If you live in a listed building or in a conservation area you may still require planning permission. Use the ‘show on map’ button on the results page to see whether you live in a conservation area or listed building. You can also see where in your area solar electricity systems have already been installed.

To enquire about planning permission please contact:

Development Management
Nottingham City Council
Loxley House
Station Street
Nottingham
NG2 3NG
United Kindom

Email: development.management@nottinghamcity.gov.uk

Tel: 0115 8764447

You can also contact the Building Control Service at the same postal address.

Email: building.control@nottinghamcity.gov.uk

Tel: 0115 8764028

For general information on planning permission for solar electricity systems see here.

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Is any maintenance required?

The panels work their best when clean and free of dust, so you will need to clean the panels to get as much solar energy as possible. However, beyond this they require little maintenance.

The inverter that the panels are fitted to will need to be replaced within the lifetime of the panels (lifetime is around 25 years). At the moment the costs of this are around £1000.

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About Solar Hot Water

Solar water heating systems collect free energy from the sun to warm the water in your house which can then be stored in your hot water tank ready for when you need to use it.

We recommend that before installing energy generation technologies such as solar water heating you improve the energy efficiency of your property as far as is practically possible. Please refer to the Energy Efficiency results for your property, the About Energy Efficiency tab and the Help with Installation page for more information on how to do this.

For further information about solar hot water and the results given by the Energy Calculator please choose from the following questions:

What can I do next to get solar hot water panels installed?

For information on local schemes which can provide support for installation and financial support available please visit the Help with Installation page.

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What are these results based on?

The results given by the Energy Calculator are based on data about properties within Nottingham. The data has not been collected in an intrusive way – it is based on information we can gain from maps.

Where we don’t have all the necessary information on the ‘real’ state of a property we have made assumptions based on information about similar properties. We have tried hard to make the data we use as accurate as possible and are confident that the Energy Calculator will provide you with useful results.

Please note though that the results that the Energy Calculator gives should be regarded as indicative and that all values should be verified by a qualified professional before installation of any measures takes place.

You can help us improve the Energy Calculator by telling us more about your property in our Survey.

The Energy Calculator also uses information on government schemes such as the Renewable Heat Incentive as well as data on energy prices in the modelling of financial savings and paybacks.

A number of tools exist on the website of the Nottingham Energy Partnership which allow you to carry out your own solar assessment, in which you can input values relating to your property and desired solar system yourself.

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The Energy Calculator says that my home may not be suitable for solar hot water – why is this?

There are two reasons why this may be the case:

  • Your property is modelled as having a north-facing roof or otherwise as receiving solar radiation of less than 815kWh/m2/year (kilowatt hours per square metre per year). This is considered to not be enough to make installation of a solar water heating system worthwhile.
  • Your property is a flat and therefore does not have its ‘own’ roof on which to put a solar hot water system. This is likely to make installation of a solar hot water system impractical as sharing the heated water amongst the flats will be difficult.

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How does solar energy heat water in the home?

Solar hot water systems use panels, called collectors, that are fitted to your roof. These should face anywhere between South-East and South-West for best performance. The panels collect heat from the sun. Water passes around the collectors and is heated as it does so. This in then stored in a hot water cylinder inside your house. A boiler or immersion heater will be needed – at least in the colder months - to heat the water further to required temperatures.

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What type of solar hot water system is assumed here?

The results given by the Energy Calculator are based on the use of an evacuated tube solar thermal system, with standard sized tubes of 47mm diameter and 1.5m length.

For more information on solar water heating systems see the Energy Saving Trust website.

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How is the Energy Generated figure calculated?

Energy Generated is calculated using SAP (Standard Assessment Procedure) 2009 methodology. This includes the use of variables including the modeled solar radiation received by the property and the system size.

The modeling is based on the use of an evacuated tube solar thermal system, with standard sized tubes of 47mm diameter and 1.5m length. Please note that tubes of different sizes are available and that the use of larger tubes would reduce the number of tubes required to produce the same amount of hot water.

Note that based on experience it has been assumed that a system size of fewer than 30 standard sized evacuated tubes would not deliver enough hot water to make installation worthwhile.

Any properties modeled as receiving solar radiation of less than 815kWh/m2/year (kilowatt hours per square metre per year) have been considered not to receive enough solar radiation to make installation of a solar water heating system worthwhile.

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How is System Size calculated?

The modeling is based on the use of an evacuated tube solar hot water system, with standard-sized tubes of 47mm diameter and 1.5m length. Please note that tubes of different sizes are available and that the use of larger tubes would reduce the number of tubes required.

Based on experience it has been assumed that a system size of fewer than 30 standard-sized evacuated tubes would not deliver enough hot water to make installation worthwhile. This 30 tube system would require a hot water cylinder with a capacity of 160 litres or greater.

Other factors such as skylights and vents have not been incorporated into our model. If these are present they may reduce the amount of solar panels your roof could accommodate.

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What is a kilowatt hour (kWh)?

The kilowatt hour is a unit of energy which integrates the amount of power used (in kilowatts) and the time it is used for (in hours). It is used to measure the amount of energy used in homes. If your home has gas-fired heating you will see that your gas bill tells you your gas consumption in kilowatt hours.

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What is kWh/year?

kWh/year means 'kilowatt hours per year'. This is the number of kilowatt hours used (or generated) annually.

kWh/year is used here to describe the amount of energy contained in the hot water generated by the solar hot water system over a year. This replaces the need for the same amount of energy to be provided through another heating fuel such as gas.

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Will I have hot water all year round?

Solar hot water systems work best in direct sunlight, but still work effectively on cloudy days. You will have hot water all year round, however you are unlikely to have enough hot water for your needs in the colder months, so you will need a boiler or an immersion heater to further heat your water to the right temperature for your needs.

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Will the water get too hot?

Some modern systems are very effective and can sometimes heat water to a temperature that poses a scolding risk (as is true with a conventional boiler).

You will be able to control the temperature at the tap as you would normally.

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Will the solar panels and cylinders freeze in winter?

No, the system is well insulated, and solar heating circuits are part-filled with antifreeze, specifically made for solar installations.

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What maintenance is required?

Maintenance costs are generally very low. Most solar water heating systems come with a five-year or ten-year warranty (although you need to check this with the installer) and require little maintenance. You should take a look at your panels every year and have them checked more thoroughly by an accredited installer every 3-5 years, or as specified by your installer.

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How is Installation Cost calculated?

Installation costs are based on a system size of 30 standard-sized evacuated tubes of 47mm diameter. Based on local knowledge average installation cost of this system is estimated at £4,000. However quotes from installers they may vary from this.

Installation costs for other types of solar hot water systems such as flat-plate collectors or evacuated tube systems of different specifications will be different.

Up to 31st March 2012 it is possible to apply for a £300 voucher towards installation of solar hot water panels through the Renewable Heat Premium Payment scheme. See here for more details of the scheme.

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How are First Year Savings calculated?

This is an estimate of the savings you could make in the first year. It includes income from the Renewable Heat Incentive scheme for generation of renewable heat using the solar hot water system, and savings made on your heating bill as a result of generating some of the hot water that you use yourself.

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What is the Renewable Heat Incentive?

The Renewable Heat Incentive (RHI) is an incentive scheme – similar to the Feed in Tariff scheme for renewable electricity generation - intended to reward those who invest in renewable heating systems.

Please note that the Renewable Heat Incentive will not be introduced for domestic installations until late 2012. However any installation made from 15th July 2009 will be eligible for RHI payments (though they will not be back-dated to the time of installation).

Final details of the domestic RHI scheme have yet to be announced. The government has indicated in its consultation document on the RHI that domestic installations of solar hot water panels will receive a tariff of 18p per kilowatt hour of renewable heat generated. Payment of this tariff would be guaranteed for 20 years and would be Retail Price Index-linked to rise with inflation. This tariff rate has been used to calculate the Energy Calculator results.

However please note that this tariff and guaranteed payment period may be subject to change before the launch of the domestic RHI. This would alter the First Year Savings and Payback period expected.

See here for more information about the Renewable Heat Incentive Scheme.

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How is Payback period calculated?

The payback period is the length of time that it will take for the financial savings (including Renewable Heat Incentive income) that result from the solar hot water system to pay back the installation cost. The period is calculated using the installation cost and the First Year Savings figure, with inflation rates applied to the latter to capture Retail Price Index-linked increases in Renewable Heat Incentive income (modelled at 3% per year) and assumed increases in gas bills (modelled at 6% per year) over time.

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How are Annual CO2 (carbon dioxide) Savings calculated?

A 30 evacuated tube system will typically generate around 600-700kWh (kilowatt hours) of heat per year, varying dependent on the amount of solar radiation the property receives.

A conversion factor is used to calculate how much carbon dioxide will be saved by heating water using solar hot water panels (which produce zero carbon) in place of using the heating fuel modelled by the Energy Calculator as currently being used in the property (this is usually gas though may be another fuel). The 30 tube system will typically save around 0.12 tonnes (120kg) of CO2 per year in a home with gas water heating. The saving will be higher where other heating fuels are used.

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Will the system work with my current heating system?

A solar hot water system does require the presence of a hot water cylinder for the storage of heated water. Therefore if your boiler is a combination (combi) boiler and you don't currently have a hot water cylinder, you would need to have a cylinder installed when installing a solar hot water system.

A competent accredited installer will be able to assess your home and help you choose the best setup to meet your needs. See our Help with Installation page for links to local installers.

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What is the lifetime of the system?

Systems usually have a lifetime of approximately 25 years.

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Do I need planning permission to install solar panels?

Domestic solar hot water systems are classed as ‘permitted development’ and therefore do not usually require planning permission, although you are advised to check in each instance with the Council.

The installer will need to be recognised as competent to assess any structural issues - such as those relating to installation of roof-mounted renewable energy systems - through being accredited under a recognised scheme. You should therefore check with an installer that they are accredited under such a scheme (and if you are unsure contact Building Control). If the installer is not accredited then you will need to notify Building Control of the works.

Installers of solar panels should also be registered under the Microgeneration Certification Scheme (MCS). We recommend that in all cases you use MCS certified installers. If the installer is not MCS accredited then you will need to notify Building Control of the works.

If you live in a listed building or in a conservation area you may still require planning permission. Use the ‘show on map’ button on the results page to see whether you live in a conservation area or listed building.

To enquire about planning permission please contact:

Development Management
Nottingham City Council
Loxley House
Station Street
Nottingham
NG2 3NG
United Kindom

Email: development.management@nottinghamcity.gov.uk

Tel: 0115 8764447

You can also contact the Building Control Service at the same postal address.

Email: building.control@nottinghamcity.gov.uk

Tel: 0115 8764028

See also the Energy Saving Trust website for general information on planning permission.

For general information on planning permission for solar hot water systems see here.

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About Energy Efficiency

The energy efficiency measures detailed within the Energy Calculator will help you keep your home warm at less cost. We recommend that you improve the energy efficiency of your home before having renewable energy technologies such as solar electricity or solar hot water systems installed.

The measures included are ‘low cost measures’ (loft insulation, cavity wall insulation and hot water tank insulation) and other measures such as upgrading heating systems, upgrading your windows to double glazing and insulating solid walls.

For further information about energy efficiency measures and the results given by the Energy Calculator please choose from the following questions:

What can I do next to get energy efficiency installed?

For information on local schemes which can provide support for installation and other financial support available please visit the Help with Installation page.

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What is the Green Deal?

The Green Deal will be launched nationally in late 2012 and will offer loans for the installation of measures to improve the energy efficiency of properties and reduce fuel bills. The loans will remove upfront costs for installation, with the scheme designed so that within a set number of years savings on fuel bills will pay back the cost of the loan.

Most energy efficiency measures are likely to be eligible for a Green Deal, although some higher cost measures such as solid wall insulation are unlikely to pay back loans quickly enough to be eligible. The government is looking to provide support for higher cost measures through the new Energy Company Obligation which will support the Green Deal.

At present Nottingham City Council is looking into the role it can play in facilitating take up of the Green Deal in the city.

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What are these results based on?

The results given by the Energy Calculator are based on data about properties within Nottingham. The data has not been collected in an intrusive way – it is based on information we can gain from maps.

Where we don’t have all the necessary information on the ‘real’ state of a property we have made assumptions based on information about similar properties. We have tried hard to make the data we use as accurate as possible and are confident that the Energy Calculator will provide you with useful results.

Please note though that the results that the Energy Calculator gives should be regarded as indicative and that all values should be verified by a qualified professional before installation of any measures takes place.

You can help us improve the Energy Calculator by telling us more about your property in our Survey.

The results given by the Energy Calculator are also based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’section for more information.

The Energy Calculator also uses financial data such as recent energy prices in the modelling of financial savings and paybacks.

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What do the different options in the drop-down box mean?

Results are generated by the Energy Calculator for six different options, the results for which can be seen by choosing the option you would like to see from the drop-down box. Each option presents a combination of different energy efficiency measures.

The six options are:

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Can you explain the different results for the different options?

For each of the options the Energy Calculator will give combined results for all of the energy saving measures which are included in the option. For example ‘low cost measures and double glazing’ will include calculations relating to the three low cost measures – loft insulation, cavity wall insulation and hot water tank insulation – and double glazing.

Calculations of Energy Saved, Installation Cost and so on will only be made for those measures which our modelling suggests are suitable for your property and which you do not already have installed. The results given will be combined figures for the individual measures considered.

For example, if you select the 'Low cost measures and heating and double glazing' option and our modelling assumes that you...

  • Have a loft but that it is not currently insulated
  • Live in a property with solid walls
  • Have a hot water tank which is not currently insulated
  • Have single glazed windows

...then the Energy Calculator will suggest that you have loft insulation, hot water tank insulation and double glazing installed. It would not suggest that you have cavity wall insulation (one of the low cost measures) installed because the property is modelled as having solid walls.

The results given will combine figures relating to these individual measures. For example the Installation Cost result given would be the sum of the installation costs calculated for the three individual measures (in this example, loft insulation, hot water tank insulation and double glazing).

You can understand which energy efficiency measures our modelling is suggesting by comparing results for the different options in the drop-down box.

For example, if in the above example our modelling instead suggested that you already have double glazing installed then there will be no difference between the ‘low cost measures’ and the ‘low cost measures and double glazing’ results (because only loft and hot water tank insulation will be recommended under both options).

If you believe that one or more of the results given could be more accurate then you can help us improve the Energy Calculator by telling us more about your property in our Survey.

We are working to improve the display of results to make them easier to interpret. If you would like to give any comments or suggestions then please complete our Feedback form.

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How is Energy Saved calculated?

The Energy Saved figure is calculated based on the current energy use of your property as modelled by the Energy Calculator and the reduction in energy use which would result from the installation of the energy efficiency measures recommended.

The Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The Energy Saved figure given for each option will therefore relate to the installation of those measures.

The figures given are calculated using SAP (Standard Assessment Procedure) 2009 methodology. Please note that this assumes that you heat the living area of the property (usually the lounge or living room) to 21°C, and that the rest of the house is nominally heated to 18°C. It is assumed that the heating system is used for 34 weeks of the year (from October to May) and that during this period it is on for 9 hours a day on weekdays and 16 hours a day at the weekend.

If you believe that you heat your home differently to this then the actual energy savings, First Year Savings, Payback period and Annual CO2 Savings resulting from the installation of energy efficiency measures are likely to differ from those suggested by the Energy Calculator.

If you currently heat your home less (i.e. to a lower temperature or for less time) than is assumed then savings are likely to be lower and the payback period longer than is suggested. Conversely, if you currently heat your home more than is assumed then savings are likely to be higher and the payback period shorter.

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What is a kilowatt hour (kWh)?

The kilowatt hour is a unit of energy which integrates the amount of power used (in kilowatts) and the time it is used for (in hours). It is used to measure the amount of energy used in homes. You may be familiar with this as it will appear on your electricity and gas bills.

For example:

  • An electric heater rated at 1 kilowatt (1000 watts), operating for one hour uses one kilowatt hour of energy.
  • Using a 15 watt light bulb for one hour consumes 0.015 kilowatt hours of electricity.
  • Using a 15 watt light bulb for one hundred hours consumes 1.5 kilowatt hours of electricity.

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What is kWh/year?

kWh/year means 'kilowatt hours per year'. This is the number of kilowatt hours used (or saved) annually.

So, for example, if a 1 kW heater is used for one hour per day for 365 days of the year it will use 365 kilowatt hours over the year (1kW x 1 hour x 365 days).

Improving the insulation in a property so that this heater was no longer required would save 365 kWh/year.

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How is Installation Cost calculated?

Installation costs are based on knowledge of average costs of the energy efficiency measures.

Note that the Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The Installation Cost given for each option will therefore be the sum of the installation costs of those measures.

The following table gives the installation costs of different measures used by the Energy Calculator to calculate results. Note that quotes from installers may vary from these figures.

Please also note that the costs used do not include discounts on the cost of measures which may be available (most often for loft and cavity wall insulation). For links to information on discounted installation schemes and other forms of financial support see the Help with Installation page.

ITEMPRICEUNITS
     
Low cost measures   
Loft insulation£6.00per m2
Cavity wall insulation£5.00per m2
Hot water tank insulation£50.00single cost
     
Heating   
Gas boiler£1800.00single cost
Oil boiler£2000.00single cost
Oil tank£1080.00single cost
Install heating controls£500.00single cost
Removal of heater£70.00single cost
Removal of heating system£200.00single cost
Addition of fused point£80.00per room
Coversion of socket to fused point£25.00per room
Radiator£300.00per room
Storage heater£400.00per room
Improved heating controls£150.00single cost
Thermostat£30.00single cost
Thermostatic raditator valves£30.00single cost
     
Double glazing   
Double glazed window£400.00per window
     
Solid wall insulation   
Solid wall insulation£87.00per m2

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How are First Year Savings calculated?

This is an estimate of the savings you could make in the first year. It includes savings made on your heating bill as a result of improvements to the energy efficiency of the property which mean that you consume less heating fuel to keep warm.

Note that the Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The First Year Savings figure given for each option will therefore relate to the installation of those measures.

Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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How is Payback period calculated?

The payback period is the length of time that it will take for the financial savings that result from the installation of the recommended energy efficiency measures to pay back the installation cost. The period is calculated using the Installation Cost and the First Year Savings figure, with inflation rates applied to the latter to capture assumed increases in energy bills (modelled at 6% per year) over time.

Note that the Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The Payback period given for each option will therefore relate to the installation of those measures.

Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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How are Annual CO2 (carbon dioxide) Savings calculated?

A conversion factor is applied to the Energy Saved figure to calculate how much carbon dioxide will be saved by the energy efficiency measures recommended.

Note that the Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The Annual CO2 (carbon dioxide) Savings figure given for each option will therefore relate to the installation of those measures.

Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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What are low cost measures?

These are measures you can take that will benefit the energy efficiency of your property at relatively small cost and are often available at discounted rates (see our Help with Installation page for more information).

The measures included are:

Note that the Energy Calculator will only recommend installation of measures which our modelling suggests you do not already have installed. The figures given will therefore relate to the installation of those measures.

Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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What is loft insulation?

Loft insulation is used to prevent heat loss from your roof. As heat rises, approximately a quarter of heat in the house is lost via your attic, loft or flat roof. Installing loft insulation will reduce this heat loss, thereby keeping your home warmer without higher energy bills. Loft insulation is effective for at least 40 years and offers very good paybacks.

Financial support and support for installation is often available, meaning that loft insulation can often be installed at reduced or no cost. See please the Help with Installation page for more information on support available in Nottingham.

Mineral wool insulation can normally be used and can often be installed by the householder. It is recommended that 250mm of insulation is installed in your loft.

If your house suffers from condensation or mould, you should consult a professional before insulating otherwise you could be making existing problems worse.

The Energy Calculator models the current amount of loft insulation in the property. This modelling may suggest that the property has no insulation, that it is partially insulated or has the full 250mm.

If the modelling suggests that you do not already have full loft insulation then the Energy Calculator will recommend that you get this installed. The results given will reflect the modelling. For example installing insulation in a property which is modelled as currently having no insulation will result in larger energy and financial savings than in a property modelled as having partial insulation (for example 100mm of insulation).

For further information about loft insulation, please see here.

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What is cavity wall insulation?

If your property is modelled as having cavity walls which are currently uninsulated then the Energy Calculator will recommend installing insulation.

Cavity wall insulation reduces heat loss through walls. It can also help reduce condensation inside the house if this is a problem on your external walls.

Insulation can be made out of mineral wool, foamed insulants, beads or granules.

Financial support and support for installation is often available, meaning that cavity wall insulation can often be installed at reduced or no cost. See please the Help with Installation page for more information on support available in Nottingham.

If you live in flats it is not usually practical to insulate a single flat in a block. If the property has cavity walls, the whole building would need to be insulated at the same time. You will need to discuss installation of cavity wall insulation with your neighbours to have the whole building insulated.

For further information about cavity walls and cavity wall insulation, please see here.

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What is hot water cylinder/ tank insulation?

Just as you get cold without a jacket, so does your hot water tank. Insulating the hot water tank with a jacket will reduce heat lost and therefore save money.

If our modelling suggests that you have a hot water tank and that it is currently uninsulated then the Energy Calculator will recommend that an insulating jacket is fitted.

For further information about insulating hot water tanks please see here.

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I am getting a result for ‘low-cost measures’ which suggests zero savings and costs. Why is this?

If our modelling of your property suggests that you already have all low cost measures installed then the Energy Calculator will not recommend installing any of them.

It will therefore give zero figures for Energy Saved, Installation Cost, First Year Savings and Annual CO2 Savings.

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What are ‘low cost measures & double glazing’?

This option gives you combined results for:

  • the three low cost measures (loft insulation, cavity wall insulation and hot water cylinder/ tank insulation),and
  • installation of double glazing
  • The Energy Calculator will give combined results for all of the energy saving measures which are included in the option. It recommends energy efficiency measures which our modelling suggests you do not currently have installed, and the figures given are based on this.

    For example, if you select this option and our modelling suggests that you...

  • Have a loft but that it is not currently insulated
  • Live in a property with solid walls
  • Have a hot water tank which is not currently insulated
  • Have single glazed windows
  • …then the Energy Calculator will suggest that you have loft insulation, hot water tank insulation and double glazing installed.

    The results given will combine figures relating to these individual measures. For example the Installation Cost result given would be the sum of the installation costs calculated for the three individual measures (in this example, loft insulation, hot water tank insulation and double glazing).

    Note that if our modelling suggests that you already have double glazing installed then there will be no difference between the ‘low cost measures’ and the ‘low cost measures & double glazing’ results.

    Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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    Can you tell me more about double glazing?

    Double glazed properties lose much less heat through windows than properties with single panes. Double glazing can reduce draughts and also help to reduce external noise heard within the property.

    Please see here for more information about double glazing and alternatives to double glazing.

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    What are ‘low cost measures & heating’?

    This option gives you combined results for:

    The Energy Calculator will give combined results for all of the energy saving measures which are included in the option. It recommends energy efficiency measures which our modelling suggests you do not currently have installed, and the figures given are based on this.

    Note that if our modelling suggests that you already have all desirable energy efficient heating system, boiler and controls installed then there will be no difference between the ‘low cost measures’ and the ‘low cost measures and heating’ results.

    Where the Energy Calculator has given results which indicate that heating measures are recommended then you should talk to an installer to gain further information on what you can have installed. See our Help with Installation page for useful links.

    Please also note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the ‘How is Energy Saved calculated?’ section for more information.

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    What heating measures are recommended?

    The figures that the Energy Calculator gives are based on the recommendation of measures as follows:

    • Where the property is modelled as being on the gas network but not using gas as its heating fuel then the installation of gas mains central heating with a condensing or condensing-combi boiler is generally recommended.
    • Where the current boiler type is modelled as a standard or back boiler then installation of a condensing boiler is recommended. Where current boiler type is modelled as a combi boiler then installation of a condensing-combi boiler is recommended. Condensing/condensing-combi boilers are the most energy efficient types of boiler – see here for more information.
    • In some cases, where the property is not modelled as being on the gas network installation of electric storage heating using off-peak electricity is recommended for smaller properties (Less than 60m2), while installation of oil-fired central heating (with a condensing boiler) is recommended in larger properties (Greater than 60m2). This is dependent on existing heating fuel type: these changes are always recommended where fuel type is modelled as standard house coal, smokeless fuel, anthracite or wood.
    • Where installation of gas- or oil-fired central heating is recommended the installation of heating controls will also be recommended. These controls are a programmer (to control at what times the boiler comes on), a room thermostat and thermostatic radiator valves. For more information on heating controls see here.

    Please note that if you wish to install a solar hot water system a hot water tank is required and a combi-condensing boiler would therefore be unsuitable.

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    What are ‘Low cost measures & heating & double glazing’?

    This option gives you combined results for:

    The Energy Calculator will give combined results for all of the energy saving measures which are included in the option. It recommends energy efficiency measures which our modelling suggests you do not currently have installed, and the figures given are based on this.

    Where the Energy Calculator has given results which indicate that heating measures are recommended then you should talk to an installer to gain further information on what you can have installed. See our Help with Installation page for useful links.

    Please note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the How is Energy Saved calculated? section for more information.

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    What are ‘low cost measures & double glazing & solid wall insulation’?

    This option gives you combined results for:

    The Energy Calculator will give combined results for all of the energy saving measures which are included in the option. It recommends energy efficiency measures which our modelling suggests you do not currently have installed, and the figures given are based on this.

    Please note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the How is Energy Saved calculated? section for more information.

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    Can you tell me more about solid wall insulation?

    Solid wall insulation is generally suitable for properties built before the 1930s. Solid walls are made up of ‘solid brick’, therefore do not have a gap to fill with insulation, unlike ‘cavity’ walls. These walls are insulated in a different way to stop heat escape.

    The only way to insulate this type of home is with ‘solid wall’ insulation which can be installed on the inside, or the outside of a property.

    Note that the calculations carried out by the Energy Calculator are for external solid wall installation.

    Solid wall insulation:

    • retains up to 45% of household heat
    • improves the thermal efficiency of a property to the same standard of cavity wall insulation
    • acts as a noise barrier
    • could increase the value of a property

    External solid wall insulation consists of a layer of insulation material which is fixed to the walls with mechanical fixings and adhesive. Protective layers of render or cladding are then applied.

    Because external solid wall insulation is likely to change the external appearance of the property it is likely to require planning permission.

    It is also possible to install internal solid wall insulation. This is less expensive, can be carried out room-by-room rather than for the whole property, but installation is disruptive and will also slightly reduce internal room space.

    For further information on solid walls please click here.

    If you live in Aspley, find out if you can benefit from free solid wall insulation by going to the Aspley Super Warm Zone website.

    You can also watch a video on youtube about installation of solid wall insulation which has taken place as part of the Aspley Super Warm Zone project.

    Although it is possible to externally insulate solid walls in flats, it is impractical to only insulate one flat in a block. You will need to discuss installation with your neighbours if you live in a flat and are interested in solid wall insulation.

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    What are ‘low cost measures & heating & double glazing & solid wall insulation’?

    The Energy Calculator will give combined results for all of the energy saving measures which are included in the option. It recommends energy efficiency measures which our modelling suggests you do not currently have installed, and the figures given are based on this.

    Where the Energy Calculator has given results which indicate that heating measures are recommended then you should talk to an installer to gain further information on what you can have installed. See our Help with Installation page for useful links.

    Please note that the figures given by the Energy Calculator are based on assumptions about how you currently heat your home. If you heat your home differently then the energy, financial and carbon savings which can be made and the payback period achieved through the installation of energy efficiency measures will be different to those suggested. See the How is Energy Saved calculated? section for more information.

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    Do I need planning permission for any energy efficiency measures?

    Planning permission is not required for most energy efficiency measures. However, if in doubt it is worth checking with the Council, particularly if you live in a conservation area or listed building, Use the ‘show on map’ button on the results page to see whether you live in a conservation area or listed building.

    External solid wall insulation is likely to change the external appearance of the property and you should therefore enquire as to whether it would require planning permission. This is the case wherever you live in the city.

    Building Control will also need to be notified when installing solid wall insulation, whether it is external or internal.

    To enquire about planning permission please contact:

    Development Management
    Nottingham City Council
    Loxley House
    Station Street
    Nottingham
    NG2 3NG

    Email: development.management@nottinghamcity.gov.uk

    Tel: 0115 8764447

    You can also contract the Building Control Service at the same postal address.

    Email: building.control@nottinghamcity.gov.uk

    Tel: 0115 8764028

    See also the Energy Saving Trust website for general information on planning permission.

    For more information about planning permission for energy efficiency projects see the Common Projects section of the Planning Portal website here.

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