SolarSums

Is a battery worth it without solar panels?

See what a battery alone could save each year, and whether it pays back.

Showing Leeds (LS1 4AP) until you enter a postcode.

Your home's use through the day

Three bars showing a year of household use in the day, evening and overnight. The evening bar is split into use covered by the battery and use bought at the day rate.

The bars show your home's use through an average day. The shaded evening hours are covered by power the battery stored overnight. The rest comes from the grid at the day rate.

Covered by the battery Grid at the day rate

Battery covers
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Of evening use
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Saving a year
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Battery cost
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Payback
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Rates
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Your home

How this works

  • Rates are live Octopus Go rates: the battery charges at the night rate and replaces power you'd otherwise buy at the day rate. Your own tariff may differ.
  • Octopus Go is only for people with an electric car they charge at home, and you also need a compatible smart meter. Without an electric car, you'd need another time-of-use tariff, and its rates may be less favourable, so check what you can get.
  • Household use follows the same split as the calculator: 35% in the day, 45% in the evening and 20% overnight.
  • A battery is modelled at 90% round-trip efficiency, so storing 1 kWh costs a little more than 1 kWh at the night rate. The saving on each kWh it supplies is the day rate minus the night rate divided by 0.9.
  • The battery covers your evening use up to 90% of its size each day. A bigger battery only helps if you use enough in the evening to empty it.
  • Battery cost, lifespan and replacement follow the calculator's defaults, which you can see on our How it works page.
  • No solar data is needed. Your postcode only sets your regional Go rates.

These figures are an illustration to help you understand your options, not financial advice or a quote.