Assumptions and workings

The figures that we state on our site are true at the time of publishing and updated regularly.

1) A south-facing roof at typical pitch in central UK, giving 855 kWh/kWp yield

2) Electricity savings calculations are based on the family being out during the day during the week

3) Property has an Energy Performance Certificate rating A-D

4) Investment based upon 4kWp polycrystalline system and a 6.5kWh LG Chem battery

5) Feed-in Tariff rates as at July 2017, tariffs paid for 20 years from the point the solar system is accredited

6) Savings of 16.0p per unit of electricity, at 5% annual inflation (source: DECC Quarterly Energy Prices, 10 year average )

7) Export tariff payments are based on a deemed export of 50%

9) Returns are tax free and can be calculated over 20 years (the lifetime of the Feed-in tariff).

Please be aware that for every quarter, the government will now cap the number of installations that qualify for the Feed-in Tariff. If the cap is reached, your solar system will be placed in a queue for the following quarter’s tariff. Your return on investment will vary depending on what Feed-in Tariff you actually get. We cannot guarantee any rates.