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.