Compare running costs for your home
Cooling costs calculated.
Figures illustrative, not a promise of savings. Room size, weather, set temperature, installation and how each machine performs change the result.
Compare the cost of the warmth delivered
| Heat source | Cost per kWh of heat delivered |
|---|---|
| Gas boiler 7.33p gas, divided by an 85% worked efficiency | 8.6p |
| Air conditioning 26.11p electricity, worked COP 3.0 to 3.5 | 7.5 – 8.7p |
| Direct electric heater 26.11p electricity, one unit in and one unit out | 26.1p |
Ofgem July to September 2026 GB-average Direct Debit default-tariff rates, including VAT: electricity 26.11p per kWh and gas 7.33p per kWh. The 85% boiler assumption comes from a 2009 field trial of ten regular condensing boilers. Figures are illustrative; region, payment method, tariff and system performance change the result.
A plug-in heater turns one unit of electricity into one unit of heat. Under the stated worked assumption, air conditioning in heating mode moves three to three and a half units of warmth for the same electrical input.
Three numbers to ask for before comparing systems
The room’s design load
How much heat the room loses in winter and gains in summer. Floor area alone does not show glazing, insulation, roof exposure or afternoon sun.
The proposed unit’s performance
Check the performance figures for the unit being proposed. A generic COP from a different unit cannot predict your bill.
Your alternative cost
Compare with what you would otherwise run in that room: direct electric, gas through the whole house or a portable cooler. The answer changes with the alternative.
A working boiler can stay
Against a working boiler, the illustrative cost per unit of warmth is near parity. We do not promise a dramatic saving or insist that the boiler comes out.
The clearer financial case is a room already heated by direct electricity, or a home that also values cooling. Zoning may reduce use, but the result depends on which rooms you heat and for how long.
Why an installation price starts with a survey
A solid-wall Victorian terrace loses heat differently from a new-build. Room size, glazing, pipe routes, electrical work and unit positions all change the design.
Fern surveys your home, then confirms the work and price discussed. The home calculator gives you a guide price before that visit.