Turn your gas use in m³ straight into kilowatt-hours and see what it costs at the live gas price. Then work out in one click how much a heat pump saves versus your gas boiler.
Your bill measures gas in cubic metres (m³), but electricity in kilowatt-hours (kWh). To know what your gas really costs, or to compare gas and electricity, you first need to convert your gas m³ to kWh. That matters the moment you think about a heat pump: it runs on electricity, while your boiler runs on gas — you can't compare them until both are in kWh.
The conversion uses the calorific value of the gas. In the UK, 1 m³ works out to roughly 11.2 kWh. Your bill applies the formula kWh = m³ × calorific value × 1.02264 ÷ 3.6, with a UK average calorific value of about 39.5 MJ/m³ and the standard 1.02264 correction factor. Multiply your m³ by about 11.2 and you have the kWh. The calculator below does it for you, with the live gas price alongside.
The second tool goes further: enter your yearly gas use and the calculator estimates — from the live electricity and gas prices — how much a heat pump saves per year versus your boiler. So you work out your heat pump savings in seconds. Prices are shown in euros, as Dymergy normalises UK energy data to EUR for cross-country comparison.
Gas is sold by volume (m³), but the heat it contains depends on its calorific value — how much energy is in each cubic metre. UK bills use the full formula:
kWh = m³ × calorific value × 1.02264 ÷ 3.6
cost = kWh × gas price per kWh
The calorific value (CV) is typically around 39.5 MJ/m³, the 1.02264 is a volume correction for temperature and pressure, and 3.6 converts megajoules to kWh. Together they give about 11.2 kWh per m³, the value used here. Both your CV and correction factor are printed on your bill. Because part of the standing charge/levies is billed per unit, in practice the cost is easiest as m³ × price per m³. This page uses the live all-in gas price (TTF market price + tax + VAT) from Dymergy's data.
The COP (coefficient of performance) shows how much heat a heat pump delivers per unit of electricity. A COP of 3.5 means 1 kWh of electricity becomes 3.5 kWh of heat — the rest comes free from the outside air or ground. A gas boiler is around 1. That's why a heat pump can heat more cheaply, even though electricity costs more per kWh: you need three to four times less of it. The seasonal COP (SCOP) is the yearly average and more realistic than the peak COP in the brochure — so 3 to 4 is a sensible assumption for most UK homes.
About 11.2 kWh in the UK (39.5 MJ/m³ × 1.02264 ÷ 3.6). So 100 m³ is roughly 1,120 kWh, and 1000 m³ about 11,200 kWh.
The energy content of delivered gas varies slightly by region and over time, typically between about 10.9 and 11.6 kWh/m³. Your supplier prints the exact calorific value used on your bill; the 1.02264 correction factor is standard for all UK meters.
It's an estimate. We use a fixed seasonal COP and current all-in market prices for gas and electricity. Your real saving depends on insulation, emitter system, climate and tariff. Use the result for the order of magnitude, and always get a home-specific survey before investing.
The live gas price (TTF market) and today's average electricity price (EPEX day-ahead, GB zone), including tax and VAT. We leave out the supplier margin because it applies to both sides and largely cancels out in the comparison. Amounts are shown in EUR (Dymergy normalises UK data to euros).
With a dynamic tariff it benefits from the cheapest hours of the day. See live when electricity is at its lowest.
See live pricesThe same prices this calculator uses are available as a live MQTT data feed for building management, EMS and installations — every quarter-hour, across 8 European countries.
See the Dymergy feed