UK calculator

Solar Battery ROI Calculator UK

Understand whether adding a battery improves or weakens the return from solar panels for your home, usage pattern and tariff.

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Quick estimate

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Enter a few key details to get an instant returns estimate.

Representative estimate

Compare solar, storage and combined investment paths.

Baseline spend without upgrades is £37,662 over 20 years.

Decision summary

Ready when you are

Add the property basics to build your initial quote. This first pass can reach up to 50% confidence before a more tailored quote is unlocked.

0% initial quote completion

Solar + battery looks strongest

Your initial quote points to solar + battery as the best investment option based on your details when modelled with our assumptions.

Projected net profit£20,958

Estimated ROI162%

Based on a 20-year horizon.

Estimate confidence0%

To increase your estimate accuracy, create a personalised quote with tailored usage, roof, installation and household details.

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Solar only

Representative estimate

Projected net profit£17,379

Payback: 8.7 yrs
Annual benefit: £825
Upfront cost: £7,200
Generation: 3,880.1 kWh

1,872.2 kWh self-consumed, 2,008 kWh exported.

Sensitivity range: £13,556 to £20,507.

How this scenario is calculated

Annual consumption uses electricity-consumption-v1-manual-seed-2026-05 at 3,800 kWh/year (good directional confidence).
Generation lookup uses UK Average at 907 kWh per kWp per year for a south-west roof.
Average semi-detached install size assumed at 4.6 kWp across 23 m2 of roof area.
Solar cost model uses £2,100 fixed plus £1,100 per kWp for semi-detached homes.
Energy prices assumed to rise by 4% per year.
Standing charge held constant at £201 per year.
Self-consumption estimated at 48% based on occupancy, day usage and storage.

Battery only

Representative estimate

Projected net profit£275

Payback: 28.4 yrs
Annual benefit: £201
Upfront cost: £5,700
Generation: 0 kWh

0 kWh self-consumed, 0 kWh exported.

Sensitivity range: £214 to £324.

How this scenario is calculated

Annual consumption uses electricity-consumption-v1-manual-seed-2026-05 at 3,800 kWh/year (good directional confidence).
Generation lookup uses UK Average at 907 kWh per kWp per year for a south-west roof.
Average semi-detached install size assumed at 4.6 kWp across 23 m2 of roof area.
Solar cost model uses £2,100 fixed plus £1,100 per kWp for semi-detached homes.
Energy prices assumed to rise by 4% per year.
Standing charge held constant at £201 per year.
Battery-only value estimated from off-peak charging arbitrage against the import tariff.

Solar + battery

Best fit today

Representative estimate

Projected net profit£20,958

Payback: 11.3 yrs
Annual benefit: £1,137
Upfront cost: £12,900
Generation: 3,880.1 kWh

2,725.8 kWh self-consumed, 1,154.3 kWh exported.

Sensitivity range: £16,347 to £24,731.

How this scenario is calculated

Annual consumption uses electricity-consumption-v1-manual-seed-2026-05 at 3,800 kWh/year (good directional confidence).
Generation lookup uses UK Average at 907 kWh per kWp per year for a south-west roof.
Average semi-detached install size assumed at 4.6 kWp across 23 m2 of roof area.
Solar cost model uses £2,100 fixed plus £1,100 per kWp for semi-detached homes.
Energy prices assumed to rise by 4% per year.
Standing charge held constant at £201 per year.
Self-consumption estimated at 70% based on occupancy, day usage and storage.

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How this is calculated

Assumptions used for this estimate

Electricity model: Representative estimate
Estimated annual use: 3,800 kWh
Model range: 2,774-5,016 kWh
Monthly shape: standard-electric
Solar system: 4.6 kW
Solar cost: £7,200
Battery: 8.3 kWh
Battery cost: £5,700
Import tariff: 28p/kWh
Export tariff: 15p/kWh
Daytime use: 45%
Energy inflation: 4%

Battery value is tariff-aware

A battery can store solar generation for evening use and may support time-of-use tariff savings. The ROI depends on the spread between import and off-peak prices, export rates, usable capacity and how often the battery cycles.

High evening demand tends to improve battery value.
A strong export tariff can reduce the need for a large battery.
Battery-only savings need a wide off-peak to peak price spread.
Round-trip losses mean stored energy is never free energy.

Compare battery against solar-only

The best question is not whether batteries are useful. It is whether the extra savings justify the extra capital cost compared with a simpler solar-only system.

FAQs

Common questions

Are solar batteries worth it in the UK?

They can be worth it for homes with suitable usage patterns, high import rates or time-of-use tariffs. They are less compelling when the extra cost is high and the battery cycles infrequently.

Is a battery worth it without solar?

Battery-only savings can work with a strong off-peak tariff and enough daily usage, but the payback case is very sensitive to tariff spread and battery cost.

How does electricity usage change payback?

Higher daytime electricity use usually improves solar payback because more generated energy offsets imported electricity. Low daytime use can still work, especially with a battery or a strong export tariff.

Which export tariff does Solar ROI assume?

The default model uses a 15p/kWh export assumption because several leading export tariffs cluster around that level, but the calculator shows assumptions clearly and the methodology explains how changing export income affects payback.

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