Worked example: one room through winter
Suppose a room needs an average 2kW of delivered heat for eight occupied hours on 180 days. That is 2,880kWh of room heat. At 26.11p/kWh, direct electric heating would cost about £752 if it truly averaged that full load. An air-to-air heat pump achieving a seasonal COP of 3.5 would use about 823kWh of electricity for the same heat, costing about £215. The indicative difference is around £537 for that assumed year.
This is deliberately a heat-for-heat illustration, not a promise. Real rooms cycle below their design heat loss, winters vary, doors open, and heat pumps spend some cold periods defrosting. Installation cost also matters. At an illustrative £2,000 installed, a £537 annual difference against direct electric suggests a simple payback below four years—but only if the usage and performance assumptions hold. Occasional two-hour use produces a much longer payback.
Summer cooling has a separate value that payback arithmetic may not capture. A homeowner already considering fixed air conditioning for a hot bedroom or loft gets winter heating from the same equipment; the relevant incremental heating-system cost can therefore be much lower than fitting a technology used only in winter.
When the existing boiler may still be cheapest
If a gas boiler is already running to heat the rest of the property, opening or balancing the radiator in one more occupied room may cost less than buying and operating separate equipment. Modern controls can help zone the home, but shutting down too many rooms can create comfort and moisture problems and may not suit the system design.
A fair gas comparison uses the current gas unit rate, the boiler’s real seasonal efficiency, electricity for pumps and controls, and how much of the home the boiler heats to deliver comfort in the target room. It should not compare the price of one purchased gas unit directly with one purchased electricity unit while ignoring that a heat pump multiplies delivered heat. Use the full air-to-air heat pump vs gas boiler comparison before deciding whether to retain, supplement or replace gas heating.
When an air-to-air heat pump is the strongest fit
The economics are most attractive where direct electric heating is the alternative: electrically heated flats, park homes, home offices, converted lofts, garden rooms and off-gas properties. Regular use, a good outdoor-unit location and an open or easily zoned layout strengthen the case. Summer overheating makes the dual-purpose value stronger again.
A reversible fixed system is also responsive. It warms occupied air quickly and can be scheduled by room. That can reduce waste compared with charging poorly controlled storage heaters or heating unused areas, although the actual result depends on controls and behaviour. Homes considering a larger change should use the dedicated guide to replacing storage heaters or electric radiators with an air-to-air heat pump.
Read how air conditioning heating units work and the detailed air-to-air cost and £2,500 grant guide. The current Boiler Upgrade Scheme route requires a qualifying full space-heating design; a single-room comparison does not by itself establish grant eligibility.
When a £25 heater is the rational answer
If the room needs heat for a few minutes on rare days, installation payback may never arrive. A portable heater can be a reasonable short-term tool where it is suitable for the space, used according to its instructions and kept clear of vulnerable people, water and combustible materials. The comparison should include convenience and safety, not just pence per hour.
Different direct electric formats change comfort. A fan heater warms air quickly but adds noise and can feel draughty. An oil-filled radiator releases heat more slowly and quietly. A radiant heater warms people and surfaces in its line of sight. At the same rated power and full-load time, none escapes the basic electricity calculation.
Five ways to reduce the heat needed
- Stop obvious draughts without blocking required ventilation or combustion air.
- Close curtains after dark and use shutters or blinds where they do not trap damaging condensation.
- Set a stable occupied temperature instead of overheating and repeatedly purging the room.
- Clean heat-pump filters and keep indoor and outdoor airflow clear.
- Address insulation, damp and heating-control problems that make any appliance work harder.
Heating only one room should not leave the rest of the home cold enough to create condensation, mould or frozen-pipe risks. Households with older people, babies or health conditions may need higher and more consistent temperatures than a simple cost comparison suggests.