UK Air-to-Air Heat-Pump Running Costs: Count the Whole System

An air-to-air heat pump can heat and cool rooms through indoor units, but it does not automatically replace every service provided by a boiler. A useful running-cost comparison makes the system boundary explicit: which rooms are heated, how hot water is made, whether bathrooms or other areas need separate heat, and when backup is used. The answer also depends on the home’s heat demand, equipment design, control settings, and actual electricity tariff.

Separate space heating from the other services

Start by listing the services in the current home: space heating by room, domestic hot water, towel rails or bathroom heat, cooking, and cooling if relevant. Then mark which service each proposed unit supplies. A living-room split system may cover the main occupied zone while bedrooms or closed rooms use another source. If hot water remains on an immersion heater, its electricity belongs in the home’s total bill even though it is not part of the air-to-air unit’s space-heating performance.

Estimate how much heat the covered rooms need, and how much electricity the heat pump will use over the season. Do not multiply a heat-pump product label by the home’s full gas use: boiler bills may include hot water, rooms the proposed system will not heat, and distribution losses. Conversely, do not count only the split unit’s meter use if the home still relies on resistance heaters or another system for unserved spaces. Show space heating, hot water, and supplementary loads separately before adding them to a whole-home total.

Read modeled performance within its boundary

The 2026 Department for Energy Security and Net Zero study models reversible air-to-air heat pumps across 39 UK scenarios. It explores dwelling types, weather files, heating patterns, and supplementary resistance heating. In certain modeled resistance-plus-air-to-air space-heating cases, the useful heat delivered per unit of electricity is about 2.5 to 4 times the resistance input. This is a result for the modeled service and assumptions, not a household bill forecast, a product’s seasonal coefficient of performance (SCOP), or a promise that a particular home will use one quarter of its present energy.

The report’s cost comparison focuses on operating costs and excludes capital cost. Its scenarios use specified weather and tariff assumptions, and the report highlights uncertainty because evidence on domestic air-to-air performance is limited. Hot-water immersion, supplementary room heating, and cooling change the total boundary. Product SCOP describes performance under a defined scheme and test basis; it does not alone tell a household’s bill because weather, controls, installation, occupancy, and unheated rooms matter.

Compare bills on a like-for-like basis

Use the home’s own annual gas and electricity statements if available. Separate heating from hot water and cooking where possible. For a proposed system, ask for an estimate of annual electricity use by service and the assumed heat-pump output, supplementary heat, and control schedule. Include the current tariff’s unit rate and standing charge, plus any time-of-use periods that align with heating demand. The Ofgem table checked on 29 October 2026 covers 1 October–31 December 2026. Its regional price-cap figures describe default tariffs for a defined period; they are not a particular household bill, and they do not describe every fixed tariff or Northern Ireland. Recheck the dates, region, payment method, and meter before applying any benchmark.

Fixed charges require a careful boundary. If the property keeps gas for hot water or a cooker, the gas standing charge may remain. If it can close the gas account, confirm with the supplier which charges actually end. On the electricity side, the household often has a standing charge regardless of whether a heat pump is installed, so it should not automatically be allocated as a new heat-pump cost. Tariff rules and prices change; see the Great Britain unit-rate and standing-charge comparison for an illustrative method.

Ask for the assumptions behind a quote

For a real home, ask which rooms and temperatures the design is intended to serve, where indoor units will be placed, how air moves with doors closed, and what supplies hot water. Ask for expected annual electricity use and the assumptions behind it, including weather, occupancy, control settings, defrost, and supplementary resistance. Confirm whether estimated use includes immersion heating, towel rails, and cooling, and whether the installation quote includes those separate systems. Compare comfort and service coverage as well as annual energy cost.

Build a range rather than a single result: warmer and colder seasons, different room-use patterns, and a higher or lower share of supplementary heat can materially change electricity use. If one estimate assumes whole-home heating and another covers only the main living area, their totals are not comparable. The useful next step is a room-by-room design and an itemized estimate matched to the home’s bills and actual tariff. The cross-fuel method explains how to normalize different fuels without importing a price example from another country.