Gas Cost Calculator

Gas heating is the most common form of central heating in the UK, used by around 23 million households. The cost depends on your boiler efficiency, thermostat settings, insulation levels and the size of your home. Under the Ofgem price cap for 1 October to 31 December 2026 the average gas unit rate is 7.97p per kWh, including 5% VAT, with a daily standing charge of 29.68p. The cap is reset every quarter, so a rate from last winter can be well out of date, and fixed tariffs typically sit 1 to 2p per kWh below it. Smart meter tariffs look much like their electricity equivalents, but with far less time-of-use variation.

A modern condensing boiler operates at 90 to 94% efficiency, meaning 90 to 94p of every pound spent on gas is converted to useful heat. Older boilers may be only 60 to 75% efficient, wasting 25 to 40% of the gas consumed. Reducing your thermostat by just 1 degree C can save up to 10% on your heating bill, typically £80 to £120 per year, and the usual move is from 20°C to 19°C rather than anything drastic.

This calculator estimates your gas costs based on your boiler type and efficiency, thermostat setting, insulation level and property size. It shows monthly and annual costs and models the saving from upgrading your boiler or improving thermostat management. Take a 3-bed semi with an 80% efficient boiler and the thermostat at 21°C. That comes to about 12,000 kWh a year, or £956.40 of gas plus £108.33 of standing charge, giving £1,064.73 in total, of which roughly £134 is available from a 93% efficient boiler and £96 from turning the dial down.

Consumption varies far more by building than by habit. At the October 2026 rate, a well-insulated 1-bed flat burns 6,000 to 8,000 kWh a year, worth £480 to £640 of gas. A typical 3-bed semi uses 12,000 to 14,000 kWh at £960 to £1,120, a 4-bed detached 16,000 to 20,000 kWh at £1,280 to £1,590, and a solid-wall Victorian terrace with poor insulation 18,000 to 25,000 kWh at £1,430 to £1,990. That last figure explains why insulation usually beats a new boiler as the first place to spend.

Cutting the bill is mostly a question of the fabric of the house. Loft insulation at 270mm saves £200 to £500 a year and cavity wall insulation £300 to £500. Draught-proofing returns £40 to £120, insulating the hot water tank £50, and thermostatic radiator valves £100 to £200 where rooms can be heated independently. A smart thermostat from Nest or Hive is worth £50 to £150. Combine them and a typical UK home saves £600 to £1,200 a year, a bigger prize than any single piece of kit.

Comparing fuels on the headline unit rate alone is misleading. Electricity at 26.32p per kWh looks more than three times as expensive as gas at 7.97p, but a heat pump delivers 3 to 4 kWh of heat for every 1 kWh of electricity it draws, which brings the effective cost down to 7 to 9p per kWh of heat. On a tariff such as Octopus Cosy, with off-peak electricity at 12p, a heat pump can reach 3 to 4p per kWh of heat and beat gas outright. Storage heaters on Economy 7 run at around 11p per kWh off-peak, still dearer than gas, but need no installation work.

The Boiler Upgrade Scheme pays a grant of £7,500 towards an air source heat pump, raised from £5,000 in October 2023. A typical installation costs £8,000 to £14,000 before the grant, leaving £500 to £6,500 to find. Eligibility means replacing fossil-fuel or electric heating in England or Wales, and since 2024 there has been no insulation or EPC condition. A heat pump cuts gas use by 75 to 80%, and because it runs 3 to 4 times more efficiently than direct electric heat, running costs usually land close to or slightly below gas. The best fit is a well-insulated home with underfloor heating or large radiators.