Northern Ireland · mid-2026 prices

Battery & Heating Savings Estimator

Work out how much a home battery charged overnight on Economy 7 could save you, what switching your oil, gas or LPG heating to a heat pump would do, and what running an electric car on the cheap night rate could save — using current Belfast energy tariffs.

Region

Tariffs, prices and grants for your area · prices in £ GBP

1

Your tariff & electricity usage

Pick your current tariff, then tell us how much you use.

How do you want to enter your usage?
Period
90 days
Used in period
1,080 kWh
Daily average
12.0 kWh
Annual estimate
4,380 kWh
62%

This is your consumptionpattern, not what you’re billed: the battery charges overnight and discharges to cover this daytime use, so you pay the night rate for it — your day-rate grid purchases are £0 once the battery is big enough. (~60% day is typical.) It sets how much load the battery shifts.

Selected baselinePower NI Standard Rate (single / 24hr)
Unit rate32.1p /kWh
Standing charge0.0p /day (£0/yr)
2

Add a home battery

Charge overnight on the cheap Economy 7 rate, use it through the day.

Saves money
Battery saving / yeari
£1,544
From night-rate arbitrage
Battery paybacki
4.4 yrs
vs £6,800 install
Net over battery lifei
£4,319
~8 yrs of use

How the battery is used

Usable capacity27.0 kWh
Daytime load to cover / day23.0 kWh
…incl. heat pump15.6 kWh
Delivered by battery / day23.0 kWh
Day-rate grid purchases£0 — all covered
Charged from grid / day25.0 kWh
Daily utilisationi85%
Full cycles / yeari311
Estimated lifespani8 yrs

Cost of stored energy

Cost per cyclei£0.97
Battery wear / kWhi11.2p /kWh
Effective battery ratei30.3p /kWh
Saving per kWh shiftedi7.1p /kWh
Lifetime energy deliveredi60,538 kWh

Annual electricity savings vs today

Switching to Economy 7 (base load)i£54/yr
Battery arbitrage (home + heat pump)i£1,544/yr
Total electricity saving£1,598/yr
The battery’s arbitrage saving covers the daytime energy it shifts to the cheap night rate — including the heat-pump load when you add one, which is why it improves the battery’s payback. Payback is gross of wear; the “Saves money” verdict and net-over-life figure include wear and capacity fade. Assumes one cycle per day. The EV (step 4) charges directly on the night rate and doesn’t use the battery.
3

Switch heating to a heat pump

Compare your oil / gas / LPG bills against an electric heat pump on the cheap rate.

The figures below price the heat pump’s electricity at the Economy 7 day rate (37.4p/kWh) — a heat pump runs through the day, outside the cheap night window. Your batteryshifts this load to the cheap night rate: that saving shows up in step 2 (the heat pump increases the battery’s utilisation and improves its payback). Size the battery to cover both your home and the heat pump.
Current heating
£1,670/yr
Heat pumpi
£2,130/yr
Saving / yeari
−£460
Paybacki
—
vs £12,000

Heat demand

Fuel energy burned / yr20,700 kWh
Useful heat delivered / yr18,216 kWh
Heat-pump electricity / yr5,693 kWh

For reference

Direct electric would use18,216 kWh
Direct electric would cost£6,815/yr
Heat-pump rate (day, pre-battery)37.4p/kWh
4

Switch your car(s) to electric

Compare each petrol/diesel car against charging an EV overnight on the cheap rate.

Each car charges as an EV at the night rate (17.5p/kWh) inside the 01:00–08:00 (GMT) / 02:00–09:00 (BST)cheap window — no home battery needed. Add a car for each vehicle (e.g. one petrol, one diesel). The cars themselves aren’t costed — you’d buy one either way — so this is a running-cost comparison only.

Car 1

£1,382/yr on petrol → £400/yr as an EV · £982/yr (5.0p/mi vs 17.3p/mi)

Fuel now
£1,382/yr
As an EV
£400/yr
Total saving / yeari
£982
Running cost only
5

Your bottom line

Combined savings and payback for the options you've included.

In your bottom line:✓ Battery✓ Heat pump✓ Electric car— toggle each in its section above.
Total saving / year
£2,120
Upfront investment
£18,800
Combined paybacki
8.9 yrs

Where the savings come from

Battery + tariff switch£1,598/yr
Heat pump−£460/yr
Electric car (running cost)£982/yr
Battery install£6,800
Heat-pump install£12,000

Net position over time

After 10 years−£797
After 15 years£1,813
After 25 years£10,250

Cumulative savings minus upfront cost, holding today’s prices flat. Each asset only earns over its own life (battery ~8 yrs, heat pump ~18yrs) with no replacement assumed. The electric-car saving has no upfront cost (the car isn’t counted) so it runs flat across the horizon.

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A shared configuration only contains your inputs and assumptions — no personal data. Loading one applies every input and updates the breakdown above; it’s also saved to your browser so it sticks.