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
£485
Monthly saving
£40
Payback
10.3 years
Example only, based on a 10 kWh battery, 8 kWh of useful peak-period usage, 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.
Quick scenarios
Start with a preset, then adjust the numbers to match your own quote or tariff.
Estimated result
£485 per year
This estimate compares the peak-rate energy avoided against the off-peak energy needed to charge the battery, including battery efficiency loss.
Estimate only. Check real tariff rates, quote details and warranty terms before buying.
See how this is calculated →Result verdict
Marginal resultThis looks marginal because the estimated payback period is longer than the warranty period.
- The battery may still appeal for backup power or energy independence.
- Pure financial payback looks weaker on these assumptions.
- Try testing a cheaper battery quote, higher peak usage, or better off-peak rate.
Assumption checks
Review these before trusting the result
Payback is longer than the warranty period
The estimated payback period is longer than the warranty period you entered. That does not automatically make the battery unsuitable, but the financial case is weaker.
Next step
Check any quote against these assumptions
If you request a home battery quote, compare the installer's numbers against the assumptions used here: installed cost, usable capacity, warranty, tariff rates, battery efficiency and expected yearly cycles.
Before accepting a quote, ask:
- What is the total installed cost including VAT?
- What is the usable battery capacity, not just nominal capacity?
- What warranty period and cycle limit apply?
- What tariff assumptions are used in the savings estimate?
- Does the system include backup power, or is that extra?
Result details
How the estimate breaks down
These figures explain the estimated saving, payback period, useful battery energy and break-even battery cost.
Monthly saving
£40
Estimated average saving per month.
Payback period
10.3 years
Estimated time to recover the installed battery cost.
Saving per cycle
£1.62
Estimated saving each time the useful battery energy is charged and discharged.
Battery energy used
8.0 kWh
Battery energy assumed to be useful during expensive peak-rate hours.
Unused capacity
2.0 kWh
Capacity not counted because your peak-period usage does not need it.
Break-even battery cost
£4,853
Maximum cost to break even over 10 years.
Important assumptionShowHide
This is a simplified estimate. It assumes the battery only saves money when it replaces electricity you would otherwise have bought at the peak rate. It does not include installation differences, battery degradation, export payments, solar generation, standing charges, VAT, finance costs or tariff exit fees.
Calculation detailShowHide
Useful battery energy per cycle: 8.0 kWh
Off-peak energy needed per cycle: 8.9 kWh
Peak cost avoided per cycle: £2.24
Off-peak charging cost per cycle: £0.62
Estimated annual saving: £485.33
Tools
Practical home battery tools
Start by estimating your battery savings, then compare real installer quotes side by side before deciding which option deserves a closer look.
Home battery savings calculator
Estimate annual saving, monthly saving, payback period and break-even battery cost using battery size, tariff rates and expected usage.
Open tool →
WorksheetHome battery quote comparison worksheet
Compare up to three battery quotes by installed cost, usable capacity, warranty, estimated annual saving, payback and backup power.
Open tool →
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.
Guides
Learn before you buy
These short guides explain the key decisions behind home battery savings, including payback period, off-peak charging and whether a battery can make sense without solar panels.
Is a home battery worth it in the UK?
Understand when a battery may make sense, when it may not, and which numbers matter most.
Read guide →
Is a home battery worth it without solar?
Learn how grid charging on cheap off-peak electricity can work even without solar panels.
Read guide →
How to estimate battery payback period
See how installed cost and annual saving combine to produce a simple payback estimate.
Read guide →
Home battery savings examples
Compare small, typical and high-usage examples to see how assumptions change estimated savings.
Read guide →
Home battery quote checklist
Know what to ask before accepting a battery quote, including warranty, usable capacity and savings assumptions.
Read guide →
Home battery quote comparison
Compare up to three battery quotes by installed cost, usable capacity, warranty, annual saving and payback.
Read guide →
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.
Why does peak-period usage covered matter?
A battery only saves money when its stored energy replaces electricity you would otherwise buy at the higher peak rate. If your battery is larger than your useful peak-period usage, the extra capacity may not improve savings.
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