Home > Scotland > Tools and calculators > Solar Energy Calculator

Solar Energy Calculator

The Solar Energy Calculator estimates the fuel bill savings you could make and the payments you could receive from the Feed-in Tariff (FITs) scheme. This is to give you an idea as to what financial benefits you may see from a PV system installed in your home.

The calculator assumes that you have a FITs eligible PV installation of up to 4kWp and that you are eligible for the FITs PV tariff indicated in the results. It provides estimates based on the information you provided and a number of assumptions to indicate what scale of financial benefit you could receive; this is to help you decide whether a PV system is for you.

Use of the tool and its outputs is not a guarantee that you will be eligible for the FITs scheme, eligible for a specific FITs tariff or that you will see the exact same fuel bill savings and FITs payments from the installation of your planned system. 

More information on FITs.

 

Postcode


Next

Property energy efficiency rating

To understand what Feed-in Tariff rate you could get, you will need to know your property's EPC rating. You will get a higher rate if your EPC is a band D or higher. If your EPC band is lower than a band D you will get the lower rate. In both cases your EPC must also be dated before the commissioning date of your new PV system.



Back Next

Property details

Every roof is exposed to different amounts of sun. This depends on your location, the slope of your roof, shading and the direction your roof faces. The map below will help you determine which direction the sunniest side of your roof faces. The typical roof slope for the average UK home is about 40 degrees.

You can also choose the size of your solar power system. Use the slider or type in a specific value and enter a quote if you have one. If you need help, see our sizing guide.

Need help?

Roof slope

30°

0° is a flat roof and 90° means that you want to install PV panels on a vertical surface such as a wall.

Need help?

Shading

Description

Use the slider to indicate how much shading you expect to have on your roof where the solar PV system will be installed.

Need help?

Roof direction

Adjust the map to find the property and then adjust the compass to align it with the desired orientation.

Need help?

Installation size

Please choose the size of the system you’re interested in installing. View sizing guide for more help.


What is the peak generation of your system in kilowatts:

Need help?

Your current monthly electricity bills

Please enter your monthly electricity bill

Installation quote

Have you received an installation quote? (optional)

Back Next
Assumptions

Your results

These results assume that your FITs eligibility date falls within the period 1 Oct - 31 December 2016.

Bear in mind that applying for FITs within this period doesn't guarantee you the generation tariff originally assigned to this period nor guarantee eligibility for funding.

For more information, please read the calculator assumptions and visit our FITs page.


Lifetime benefits of the system


Refer to the assumptions link above. You can adjust the installation costs by entering your quote value in the previous screen, just click on the 'Back' button further down.

kWp
kWh
 tonnes of CO2

These results assume that your FITs eligibility date falls within the period 1 Oct - 31 December 2016.

Bear in mind that applying for FITs within this period doesn't guarantee you the generation tariff originally assigned to this period nor guarantee eligibility for funding.

For more information, please read the calculator assumptions and visit our FITs page.


Lifetime benefits of the system


Refer to the assumptions link above. You can adjust the installation costs by entering your quote value in the previous screen, just click on the 'Back' button further down.

kWp
kWh
 tonnes of CO2
Back Download report


Next steps

For free, independent and local energy saving advice (including further information on installing solar panels on your home) and for information on local installers, call Home Energy Scotland on 0808 808 2282

 

Sign up to Energywire, our monthly e-newsletter, for energy saving tips, news and more.


Solar Energy Calculator - Property details

Every roof is exposed to different amounts of sun. This depends on your location, the slope of your roof, shading and the direction your roof faces. The map below will help you determine which direction the sunniest side of your roof faces. The typical roof slope for the average UK home is about 40 degrees.

You can also choose the size of your solar power system. Use the slider or type in a specific value and enter a quote if you have one. If you need help, see our sizing guide.

Solar Energy Calculator - Property details

Every roof is exposed to different amounts of sun. This depends on your location, the slope of your roof, shading and the direction your roof faces. The map below will help you determine which direction the sunniest side of your roof faces. The typical roof slope for the average UK home is about 40 degrees.

You can also choose the size of your solar power system. Use the slider or type in a specific value and enter a quote if you have one. If you need help, see our sizing guide.

Solar Energy Calculator - Property details

Every roof is exposed to different amounts of sun. This depends on your location, the slope of your roof, shading and the direction your roof faces. The map below will help you determine which direction the sunniest side of your roof faces. The typical roof slope for the average UK home is about 40 degrees.

You can also choose the size of your solar power system. Use the slider or type in a specific value and enter a quote if you have one. If you need help, see our sizing guide.

Solar Energy Calculator - Roof slope

If you have a flat roof, panels can be angled when installed. The optimum angle for solar power collection in the UK is 35°.

One way of determining the slope of your roof is to look at the rafters on your attic. Use the default of 40° if you are unsure as this is the typical for a UK roof.

Solar Energy Calculator - Overshading

Shading from nearby obstacles, such as trees and buildings, will reduce the solar energy that reaches your PV panels, and therefore reduce the electricity generated. 

Ideally you would only install panels on roofs with no nearby obstructions, but that isn’t always possible.

Solar Energy Calculator - Roof direction

You can use the map to see which way the best side of your roof is facing. The closer you can be the better but it doesn't have to be exact. The best direction for solar power collection in the UK is south facing.
If you have a flat roof your panels can face any direction.

Solar Energy Calculator - Installation size

Solar electricity systems are given a rating in kilowatts peak (kWp). This is the rate at which they generate electricity at peak performance, for examples at noon on a sunny day. The capacity (kWp) of a domestic system will vary depending on how much a customer wants to spend and the roof area available to accommodate the panels. Typically system sizes are between 1-4 kWp

Solar Energy Calculator - Monthly electricity bills

An average 3-bedroom gas-heated home in the UK uses about £50/month of electricity (this is around 3,950 kWh each year). You don’t have to be too accurate with the figure as it is only used to give you a guide to what percentage of your home’s electricity will be delivered by your solar panels.

Solar Energy Calculator - Assumptions

This calculator estimates the performance of domestic solar photovoltaic (PV) systems. Its calculations account for the local effects of incident solar radiation (sunlight), ambient air temperature, wind speeds, roof direction and roof slope.
The performance of solar PV systems is impossible to predict with certainty due to the variability in sunlight from location to location, and from year to year. Whilst the estimates from the Solar Energy Calculator are based on the best information available, they should not be considered as a guarantee of performance.

This calculator is designed to give estimates for those who have not yet installed a PV system and it cannot provide estimates of Feed-in Tariff scheme (FITs) payments based on previous FITs rates for a PV system already installed.

Your actual fuel bill savings will depend on a number of factors including the size, efficiency and location of your PV system and how much electricity you use when the system is generating. 

Your eligibility for the FITs scheme and the tariff rate you receive depends on several factors including the installer and PV product you use, your home’s Energy Performance Certificate (EPC) rating before you install the system, the installed capacity of systems applied for ahead of you and the date your system was commissioned. Please note that applying within a tariff period does not guarantee the generation tariff assigned to that period nor guarantee eligibility for funding as deployment caps may be reached which could affect your application.

For the avoidance of doubt, the results in this calculator are not exactly the same as those estimated by the Standard Estimation Method which is used by MCS certified installers in solar PV quotations. The methodology used in this calculator is based on the Government's Standard Assessment Procedure (SAP) 2012 which uses different assumptions for the average level of solar radiation in an area.

This calculator is regularly reviewed and updated to reflect changes in electricity prices, FITs rates and any new statistics relating to equipment performance and electricity use in the home.

 
Calculation assumptions

This calculator presents financial performance in ‘real’ accounting terms (i.e. in today’s money). Calculations do not include any annual FITs rate adjustments due to changes in the Retail Price Index (RPI), nor inflationary costs for electricity (imported) over the lifetime of the system.

The lifetime of the FITs payments is 20 years. This is 5 years less than the 25 year expected lifetime of a PV system and this period is used to calculate fuel bill and CO2 savings. This means the total lifetime financial benefits are based on 20 years of FITs payments and 25 years of fuel bill savings.

No maintenance costs have been included in our calculations (e.g. replacing the inverter or inverter components). Typically an inverter will need to be replaced once during the lifetime of the system, costing around £800; however this will vary depending on the type of inverter installed.

The calculator uses current and estimated forthcoming FITs tariffs and assumes your scheme eligibility date. The eligibility date is the date decided by Ofgem from when FITs payments can be made to you and is only confirmed at that point. The eligibility date and tariff used by the calculator may be different to the eligibility date and tariff you finally secure. Refer to our FITs page for more detail. 

The FITs payments are based on a payment for the total amount of electricity generated by the PV system (using the FITs generation tariff) and a payment for the assumed (deemed) amount of electricity exported to the national electricity grid (using the FITs export tariff). The deemed amount is 50% of the total generation.

The electricity price used is 13.86p/kWh (based on domestic use in 2015-2016)

For estimates of electricity bill savings it is assumed that 25% of the electricity generated by the PV system is used at home up to a maximum of 500kWh, with the other 75% exported to the grid. This differs from the assumptions used to calculate the FITs export payments which is deemed at 50% regardless of how a household uses electricity. 
The amount of electricity generated by PV panels is assumed to decline steadily over time, with the performance in year 25 assumed to be 80% of the performance in year 1. 
For estimates of the carbon emissions impact, national grid electricity is assumed to have a carbon intensity of 0.496 kgCO2 /kWh.