Calculator

Solar Battery Calculator

Check whether a battery makes sense on top of your PV system. The calculator estimates self-consumption with battery, added annual battery value and battery payback.

Energy

Inputs

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The solar battery calculator does not evaluate the whole PV system, but the battery as an additional investment. It shows how much PV surplus the battery can roughly shift into self-consumption and whether that added value can justify the battery cost.

Display currencyChoose the currency symbol for entered amounts and results. No exchange-rate conversion is applied.

UnitsChoose metric, US or UK units for distance, area, volume and car consumption.

Annual PV yield (kWh)

If you do not know annual yield: system size in kWp × roughly 900–1,000 kWh/kWp/year as a first estimate.

Annual household electricity use (kWh)

You can find this number on your electricity bill. It limits how much solar power can realistically be used on site.

Directly used solar power without battery (%)

Rough assumption for solar power used immediately without a battery. Around 25–40% is common. Self-consumption with battery is then calculated as an output.

Battery capacity (kWh)

Usable battery capacity. The calculator estimates how much PV surplus can be shifted for later self-use per year.

Battery cost ($)

Additional cost for the battery only, including installation.

Electricity price ($/kWh)

Feed-in tariff ($/kWh)

Assumed battery lifetime (years)

Planning assumption for economics. The shorter the lifetime, the harder it is for the battery to pay off.

FAQ

Frequently asked questions

Does a solar battery always pay off?

No. It pays off economically only if the additional self-consumption offsets the extra cost over its lifetime.

What battery size makes sense?

Battery size should match PV surplus and evening or night demand. An oversized battery is used less often and can pay back more slowly.

Why does the feed-in tariff matter?

Stored electricity would often otherwise have been exported. The economic value is therefore electricity price minus forgone feed-in tariff.

Is battery payback certain?

No. It is a rough estimate. Load profile, weather, efficiency, ageing and electricity prices can materially change the result.

Does a battery increase autonomy?

Usually yes. But economics and autonomy are not the same: more independence can be valuable even when financial return is lower.