Independent UK planning tool

Solar and battery calculator

Use this calculator to compare solar-only, smaller-battery and larger-battery scenarios for a UK home. It models roof direction, shading, household use, tariffs and extra electric loads, and shows every core assumption behind the result. The output is an early screening estimate, not an installer design, structural survey, regulated financial recommendation or promise of future savings. Use it to make quotations easier to question, then ask an MCS-certified installer for a property-specific generation model and itemised price.

Solar & battery planner

Start with your household, not a product.

Adjust the basics to compare a sensible starting scenario. This is an indicative screening tool, not a quotation.

Try a representative household

Annual electricity use 3,600 kWh UK region Half-hourly usage profile Weekday occupancy Weekend occupancy Primary roof direction Secondary roof direction Panels on secondary roof 0% Roof pitch Shading Maximum panels that fit 12 Panel rating Import tariff 27p/kWh Tariff type Export tariff 12p/kWhDefault reflects Energy Saving Trust's typical export payment in September 2026. Source.

Electric loads EV annual mileage 0 miles EV charging pattern Heat pump? Electric water heating

Financial assumptions Heat-pump electricity override 4,200 kWhAdvanced mode only. Used when a heat pump is selected. Actual quote, if available (£) Panel degradation 0.5%/yr Battery efficiency 90% Electricity-price inflation 2.5%/yr

Your three-scenario comparison

4.0kWp modelled solar array

Estimated annual generation3,330 kWh

Worth a detailed quoteYour inputs suggest solar is worth proper modelling.

How generation is calculated

Panel count × panel wattage gives array size. Regional yield is then adjusted for the weighted roof directions, pitch, shading and first-year output.

How savings and export are calculated

Directly used solar and usable battery discharge avoid the import tariff. Remaining exported electricity earns the entered export tariff. On an off-peak tariff, overnight grid charging is valued at day rate × efficiency minus night rate, and is capped at 85% of one cycle per day.

How payback is calculated

Nominal payback uses today’s annual benefit. Inflation-adjusted payback accumulates annual benefit with electricity-price inflation and panel degradation for up to 30 years.

Your next steps

Ask your installer

Check funding pathways Compare suitable battery sizes

Battery size guide

Compare capacity with the job it needs to do.

These are category guides, not product rankings. Your planner result links here with the closest capacity highlighted.

Compact

3–5 kWh

Often suits lower-use homes, modest evening demand or households prioritising regular cycling over backup duration.

Balanced

6–10 kWh

Commonly considered for family homes with useful daytime solar surplus and meaningful evening consumption.

Large

11–13.5 kWh

Best tested carefully against high demand, EV charging, heat pumps or backup goals to avoid paying for unused capacity.