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Solar calculators

Four free calculators for UK homes. They run in the Be Solar Wise app, in your browser, and give rough estimates to help you check quotes and ask better questions.

• Battery size and payback calculatorEnter your yearly electricity use, your tariff and a battery price. It suggests a battery size and works out the yearly saving and simple payback, and compares that with a battery's typical life.
• Solar generation estimatorChoose where you are in the UK, the size of system, which way the panels face, their angle and any shade. It estimates the yearly and monthly generation and what it could be worth.
• Inverter size checker (rooftop solar)Enter your panels and your supply. It compares inverter sizes, shows the DC to AC ratio, estimates the energy lost to clipping and says whether each option fits the G98 limit.
• Plug-in solar savings calculatorEnter your kit, where it will go and how much you are at home in the day. It estimates what the kit makes, how much you will use, the saving and the payback.

How the estimates are made

• Generation: a typical yearly output per kWp for your latitude, adjusted for direction, angle and shade, with a typical monthly pattern. Well-sited UK systems usually make around 750 to 1,100 kWh a year per kWp.
• Value: Ofgem's average price cap rate for October to December 2026 (26.32p per kWh, with no VAT until 31 March 2027) and a typical export rate of 12p, which you can change.
• Batteries: the four-step sizing method in our batteries guide, with a 10% reserve and 90% round-trip efficiency.
• Inverters: the G98 limit of 16 amps per phase (about 3.68 kW single-phase) and a typical UK clipping curve.

Updated 2026-10-02.