Start with your bills. Add up the kWh you used in the last twelve months, then divide by what one kW of panels makes in a year where you live.
A quick example
- Yearly use: 9,600 kWh
- One kW makes about 1,300 kWh a year with 4.5 sun hours
- 9,600 ÷ 1,300 = 7.4 kW
- 7.4 kW ÷ 430 W panels = 18 panels
What changes the answer
- Shade from trees, chimneys and neighbours
- The direction and pitch of your roof
- Plans for an electric car or a heat pump
Size for the home you will have in five years, not the one you have today. Priya, solar design engineer
Try our savings calculator for a first figure, then book a free home survey for a design.
