This will depend on how well your property is insulated and the type of heat emitters (underfloor heating or radiators). Most heat pumps cannot produce high flow temperatures and therefore your property will not heat up quickly from cold. For this reason, they run most efficiently by maintaining the property at a constant temperature with underfloor heating or fan-convectors designed for low flow temperature systems. Traditional radiators can be used but may need to be oversized.
The latest generation of heat pumps is capable of delivering much higher temperatures, similar to that of fossil fuel boilers, although they will be slightly less efficient while doing so.
The design of the heating system is crucial, whether you are using underfloor heating or radiators, so that the system is capable of giving out sufficient heat for each room.
For some older properties where an air source heat pump alone may not cope at the coldest times of the year can be docked with a fossil fuel boiler to provide supplemental heat. Such systems allow the homeowner to enjoy all the efficiencies and benefits of a heat pump whilst ensuring they remain warm all year.