Solar sizing
Estimate solar kWp and panel count from annual demand, roof space, orientation and UK location.
Independent UK planning tool
UK Solar & Battery Calculator
Estimate a sensible solar array and home battery for your electricity use, roof and tariffs—before speaking to installers or comparing quotations.
Free to use. No registration required.
More than a panel-count estimate
Explore the whole household energy picture
Home battery sizing
Compare a suggested storage range with your chosen usable capacity and inverter limits.
EV electricity use
Include driving demand once, without accidentally duplicating it in household consumption.
Off-peak tariffs
Explore grid charging and tariff optimisation when a suitable off-peak window is available.
Import and export
See estimated solar generation, household self-use, grid import and electricity exported.
Savings and payback
Use your own tariff and installed-cost assumptions to compare annual benefit and simple payback.
Illustrative UK example
A household using 4,000 kWh a year
Suppose a home has space for ten 440 W panels, giving a 4.4 kWp array. At an assumed yield of 900 kWh per kWp, estimated annual generation is about 3,960 kWh.
If 45% is used directly, around 1,782 kWh avoids grid import before battery shifting. The remaining generation is either stored or exported. A battery can increase self-consumption, but its financial value depends on when the home uses energy, conversion losses, tariff spreads and the installed cost entered by the user.
- Annual demand
- 4,000 kWh
- Solar array
- 4.4 kWp
- Panels
- 10 × 440 W
- Estimated generation
- 3,960 kWh/year
This is an arithmetic example, not a performance or savings promise. The calculator lets you replace these assumptions with details relevant to your home.
UK solar and battery questions
Frequently asked questions
How many solar panels do I need in the UK?
It depends on annual electricity use, panel rating, roof space, orientation and local solar yield. The calculator estimates panel count and array kWp, then limits the result to the roof space you enter.
What size home battery do I need?
Battery sizing depends on how much electricity you use and when you use it—not annual kWh alone. Solar surplus, off-peak charging, usable depth of discharge, power limits and backup goals also matter.
Is a solar battery worth it in the UK?
Not always. A battery can improve self-consumption or shift off-peak electricity, but losses and additional installed cost may worsen simple payback. The calculator is allowed to show that storage does not improve the modelled economics.
Can I include an electric car in a solar calculation?
Yes. Entering EV mileage adds an estimated charging demand to household electricity use. Actual benefit also depends on whether charging happens during solar generation or an off-peak tariff window.
Can a battery charge overnight on a cheap tariff?
A compatible battery inverter/charger and tariff can make this possible. The financial result depends on the peak/off-peak price difference, battery efficiency, available charging hours and supplier terms.
Does the estimate replace an installer or electrical design?
No. It is an early-stage comparison. Roof structure, shading, cable sizing, protection, product compatibility, DNO requirements and final electrical design require competent professional assessment.
Start with your own assumptions
Build your solar plan
Enter your postcode, electricity use and roof information for a quick estimate, or open Advanced mode for technical controls.