AI-generated model house
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Home energy, in numbers.
Check them with your own.
Batteries, heat pumps and tariffs for homes in England and Wales. No installers, no sales calls, no affiliate links. Just the sums, on screen, with your own prices.
Start here
What are you trying to decide?
Pick the question. Each calculator does the same sums as its video, and nothing you type leaves this page.
Is a home battery worth it?
The main calculator: your quote, your battery and your tariff in one place. See the payback, what price would pay back, and the sums behind it. Starts from the examples in videos 1 and 3.
Open the calculator → Heat pumpsHeat pump or gas boiler?
Our model house in London, a gas boiler against a heat pump. See the yearly running cost, the SPF at which they break even, and the sums behind it, on the standard tariff or a Cosy scenario.
Open the calculator →Coming from a video? Jump to its calculator:
Have your bill or quote to hand. It helps to know your day and night rates in pence per kWh, and the total price on the quote. Questions to ask an installer
Every number is labelled
✓ Documented a fact with a source and a date ◆ Chosen an example we picked, change it ? Unknown nobody can know it for your home How to read themDates to watch
Dates that change your numbers
What changes on each date is logged on the Corrections page.
Videos
Watch here, or on YouTube
Nothing is sent to YouTube until you press play. Then the video loads from YouTube (Google) in privacy-enhanced mode, which shares your IP address with YouTube, and YouTube’s own rules apply, including storing data on your device.
Prices now
The price cap our examples use
London, direct debit, single-rate meter, 1 October to 31 December 2026. A reference, not your answer: a battery works by using cheaper power later, so the calculators also take your night or off-peak rate.
✓ Documented Ofgem price cap tables, London (region C), read on 12 November 2026. Valid until 31 December 2026. Gas includes 5% VAT. No VAT on electricity from 1 October 2026 to 31 March 2027. Your own prices will differ, so check your bill. The next cap is expected around 25 November 2026 (to be confirmed); this box will then be updated.
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