A heat pump uses electricity to move heat. Its performance depends on the complete heating system and the conditions in which it operates.
Think about heat, not just the box
The outdoor unit is only part of the proposal. A design also needs to consider heat loss, emitters such as radiators, hot water, controls and available space. Replacing a boiler is not simply a matter of swapping one rated output for another.
Ask for seasonal performance
An efficiency figure at one test condition does not describe an entire heating season. Ask how the expected performance was estimated for your home, your climate and the required water temperatures. Keep electricity prices separate from efficiency when comparing running costs.
Make comfort part of the brief
Describe rooms that feel cold, your preferred temperatures and hot-water routines. Ask about noise, maintenance access and operation in colder weather. A good handover should explain controls and how to identify a problem without encouraging unsafe adjustments.
Separate the three main jobs
Space heating, hot water and controls all need a place in the design. An air-to-water system supplies a water-based circuit; an air-to-air system supplies warm air and does not automatically replace your hot-water arrangement. Write down which services the proposed installation covers. This avoids comparing a quote for room heating alone with one that also includes a cylinder, plumbing changes and a complete controls package.
Translate performance into electricity demand
For a calculation example, delivering 12,000 kWh of heat at a seasonal performance factor of 3 requires about 4,000 kWh of electricity. At a factor of 4, it requires about 3,000 kWh. Multiply by the relevant electricity price to compare the energy cost, then add other charges. Ask whether the performance estimate includes hot water, auxiliary heaters and circulating pumps so the boundary of the calculation is clear.
Understand the importance of the emitters
Radiators or underfloor heating must deliver the required room heat at the proposed water temperature. Ask for the design temperature and any emitter changes room by room. Large temperature jumps and short bursts of operation may not match the intended control strategy. At handover, have the installer explain the normal schedule, weather compensation if fitted, holiday settings and the difference between a comfort adjustment and an engineering setting.
Your planning checklist
- Room heat-loss assessment and proposed emitter changes.
- Space heating and hot-water requirements priced separately.
- Seasonal performance with the calculation boundary stated.
- Unit location, controls demonstration and maintenance access.
Common questions
Will every radiator need replacing?
Not necessarily. The answer depends on each room’s heat requirement and the output of its existing radiator at the planned water temperature. Request that assessment instead of assuming either that every radiator stays or that every radiator must go.
Can I compare a heat pump with my old fuel bill directly?
Start with the useful heat requirement, not just the amount of fuel bought. The old system’s losses and any change in comfort or hot-water use affect the comparison. Apply consistent assumptions to both options.