Reviewed by Mustafa Bilgic
Founder, WebCalculator
Energy rates from Ofgem Q3 2026 price cap. Heat demand estimates are simplified — actual costs depend on building fabric, outdoor temperature and boiler efficiency. Not financial advice.
This heating cost calculator estimates the cost of heating a room or your whole home by fuel type, room size and insulation level. It uses the Ofgem Q3 2026 price cap rates — gas at 7.33p/kWh and electricity at 26.11p/kWh — so you can compare gas central heating against electric heaters and see where your money goes.
Per hour, per day, per month
The heat demand of a room depends on its size, insulation quality and the temperature difference between inside and outside. The calculator uses a simplified model: room area multiplied by a watts-per-square-metre factor (80W/m² for well-insulated, 110W/m² for average, 150W/m² for poor insulation). This gives the kilowatt capacity needed, then multiplied by hours and fuel rate.
For gas central heating, the boiler is assumed to be 90% efficient (modern condensing boiler). That means for every 1 kWh of gas consumed, 0.9 kWh of useful heat reaches the room. Older non-condensing boilers may be only 70-80% efficient, costing more per unit of heat.
| Fuel | Rate (Q3 2026) | Efficiency | Effective cost/kWh heat |
|---|---|---|---|
| Gas (condensing boiler) | 7.33p/kWh | ~90% | ~8.1p |
| Electric heater | 26.11p/kWh | ~100% | ~26.1p |
| Air source heat pump | 26.11p/kWh | COP ~3.0 | ~8.7p |
Rates from Ofgem Q3 2026 price cap: gas 7.33p/kWh + 29.04p/day standing charge, electricity 26.11p/kWh + 57.19p/day standing charge.
Insulation first. Loft insulation (£300-£500 DIY) and cavity wall insulation (£500-£1,500 installed) cut heat loss dramatically and have payback periods of 2-5 years. Draught-proofing doors and windows costs under £100 and makes an immediate difference.
Draught-proofing. Before spending on insulation, check for draughts around doors, windows, letterboxes and loft hatches. Draught-proofing is the cheapest energy upgrade — a complete DIY kit costs under £100 and can save £40 to £60 per year. Chimney balloons block heat loss through unused chimneys.
Smart thermostat. Heating only the rooms you use, only when you are home, and dropping the temperature by 1°C (saves ~10% on the bill) can save £100-£200 per year with no loss of comfort.
Heat pump upgrade. An air source heat pump delivers ~3 kWh of heat per 1 kWh of electricity, making it almost as cheap as gas per unit of heat — and cheaper on an off-peak tariff. The BUS grant provides £7,500 towards installation. See the heat pump cost calculator for the full comparison.
To estimate your total heating bill rather than a single room, add up the floor area of all heated rooms (typically 60 to 100 m2 for a 3-bed semi). Multiply by the W/m2 factor, the daily heating hours, and the number of heating days per year (roughly 200 in the UK). A 75 m2 averagely insulated home heating 6 hours a day for 200 days needs about 9,900 kWh of heat — roughly £726 per year on gas or £2,584 on electric panel heaters. This aligns closely with the typical £977 gas heating figure in the Ofgem typical domestic consumption model.
The energy bill calculator provides a simpler annual estimate based on total kWh consumption. Use it alongside this per-room tool for a complete picture.
The energy bill calculator estimates your total annual gas and electricity bill. For the investment case for solar panels, see the solar panel payback calculator. The water bill calculator covers your other major household utility.
A gas central heating system costs roughly 7 to 12p per hour to heat a medium-sized room, depending on room size and insulation. An electric heater (2kW fan or convector) costs about 52p per hour at the Ofgem Q3 2026 cap rate of 26.11p per kWh. Gas is typically 3 to 4 times cheaper per kWh than electricity.
Gas is significantly cheaper per unit of heat. The Ofgem Q3 2026 cap rate is 7.33p per kWh for gas versus 26.11p per kWh for electricity. A gas boiler at 90% efficiency delivers heat at about 8.1p per useful kWh, while an electric heater at nearly 100% efficiency costs 26.11p per kWh — more than three times the price.
A well-insulated medium room (16 square metres with a 2.4m ceiling) needs roughly 1 to 1.5 kW of heating capacity. A poorly insulated room of the same size may need 2 to 2.5 kW. The actual kWh consumed depends on how long the heating runs — 1.5 kW for 3 hours uses 4.5 kWh.
Gas central heating is the cheapest conventional option. An air source heat pump is the cheapest electric option because it delivers 3 to 4 kWh of heat per 1 kWh of electricity consumed. For spot-heating a single room, an infrared panel heater can be cheaper than a fan heater because it heats objects directly rather than air.
A typical UK household uses about 30 to 50 kWh of gas per day for heating during winter months. At 7.33p per kWh (Ofgem Q3 2026 cap), that costs roughly £2.20 to £3.67 per day for gas. Add the daily standing charge of 29.04p and the total is about £2.49 to £3.96 per day.
Yes. Turning your thermostat down by 1 degree Celsius typically saves around 10% on your heating bill. A programmable or smart thermostat that only heats when you are home and adjusts room by room can save £100 to £200 per year compared to a fixed schedule with no zoning.
The calculator defaults to the Ofgem Q3 2026 price cap rates effective 1 July to 30 September 2026: electricity at 26.11p per kWh with a daily standing charge of 57.19p, and gas at 7.33p per kWh with a daily standing charge of 29.04p. Source: Ofgem default tariff cap level announcement.