UK energy savings calculator
UK Home Battery Savings Calculator
Estimate whether charging a home battery on cheap overnight electricity and using it during peak-rate hours could reduce your annual electricity bill.
Example result
Estimated annual saving
£607
Monthly saving
£51
Payback
8.2 years
Example only, based on a 10 kWh battery, 28p peak rate, 7p off-peak rate, 90% efficiency and 300 cycles per year.
No sign-up
Use the calculator immediately without creating an account or entering personal details.
No data stored
The calculator runs in your browser. Your inputs are not saved to a database.
Transparent maths
The result is based on simple assumptions you can change yourself.
Free UK calculator
Estimate your home battery savings
Enter your battery size, tariff rates and expected battery use. The calculator estimates how much money could be saved by charging overnight and using the battery during peak-rate hours.
Your assumptions
The default values are only a starting example. Change them to match the tariff and battery setup you are considering.
Estimated result
£607 per year
This estimate compares the peak-rate energy avoided against the off-peak energy needed to charge the battery, including battery efficiency loss.
Monthly saving
£51
Estimated average saving per month.
Payback period
8.2 years
Estimated time to recover the installed battery cost.
Saving per cycle
£2.02
Estimated saving each time the battery is charged and discharged.
Break-even battery cost
£6,067
Maximum cost to break even over 10 years.
Important assumption
This is a simplified estimate. It does not include installation differences, battery degradation, export payments, solar generation, standing charges, VAT, finance costs or tariff exit fees.
Calculation detail
Peak cost avoided per cycle: £2.80
Off-peak charging cost per cycle: £0.78
Estimated annual saving: £606.67
How it works
The calculator compares cheap charging against peak-rate usage
A home battery can reduce electricity costs when it charges during cheaper off-peak hours and discharges later when electricity is more expensive.
This calculator estimates the cost of charging the battery, the peak-rate electricity avoided, and the possible yearly saving.
The result is not a guarantee. It is a starting estimate to help you understand whether a home battery is worth investigating further.
Checking a battery quote
Use the calculator to sanity-check whether a quoted battery cost looks realistic against the likely annual saving.
Comparing peak and off-peak rates
See how much difference a cheaper overnight rate could make when paired with a home battery.
Estimating payback period
Get a rough payback estimate before spending time speaking to installers or tariff providers.
This calculator is useful if...
- You are considering a home battery.
- You have or are considering a cheap overnight electricity tariff.
- You want a quick estimate before requesting quotes.
- You want to compare battery cost against possible savings.
This calculator is not enough if...
- You need a guaranteed financial forecast.
- You want a full solar generation model.
- You need battery degradation modelled precisely.
- You need personalised regulated financial advice.
FAQ
Common questions
Is this calculator only for the UK?
Yes. The wording, assumptions and examples are aimed at UK households using pence per kWh and pounds sterling.
Does this include solar panels?
Not yet. This first version focuses on charging a battery from cheap off-peak electricity and using it during peak-rate hours. Solar modelling can be added later.
Does the calculator store my data?
No. The calculator runs in your browser and does not store your inputs in a database.
Why does battery efficiency matter?
A battery loses some energy when charging and discharging. The calculator accounts for this by increasing the amount of off-peak electricity needed to deliver the usable battery capacity.
What does cycles per year mean?
A cycle means charging and discharging the battery. If you expect to use the battery most days, a value around 300 cycles per year is a reasonable starting assumption.
Is the payback period guaranteed?
No. The payback period is an estimate only. Real savings depend on your actual household usage, tariff, installation cost, battery settings, battery degradation and future electricity prices.
Important
Use this as an estimate, not a promise
This calculator is designed to help you make a rough comparison. It does not replace a detailed installer assessment, tariff comparison, battery specification review or financial advice.
Privacy-first by design
The calculator does not ask for your name, email address, postcode or phone number. The first version does not use a database, login system or quote form.
Try the calculator