It starts with a heat loss survey
A heat pump has to be sized for your home, room by room. A proper survey measures each room and its walls, windows, floors and ceilings, and works out how much heat each one loses on a cold day. That gives the size of heat pump you need and shows whether each radiator can do its job.
Solid walls, high ceilings and draughty sash windows lose more heat. That usually makes an older home a sizing question rather than a reason to rule a heat pump out.
Lower flow temperatures, bigger radiators
A gas boiler often sends water round the radiators at 60 to 70°C or more. A heat pump is most efficient running much cooler, often at 50°C or below, so the radiators feel warm rather than hot and run for longer.
Cooler water means each radiator gives out less heat, so some rooms may need a larger one. Often it is a few rooms, not the whole house, and the survey shows which. Narrow microbore pipework may need upgrading in places. If you are replacing floors anyway, underfloor heating works particularly well with a heat pump.
Insulation helps, but it is not a precondition
Loft insulation, draught-proofing and better windows cut the heat your home needs. That can mean a smaller heat pump, fewer radiator changes and lower running costs, so they are worth doing when you can. You do not have to finish them first: a heat pump designed for your home as it is now is sized to heat it as it is now.
We will not promise savings without the numbers. Running costs depend on the design, your electricity tariff and how you use the heating.
You will need a hot water cylinder
Heat pumps do not heat water on demand the way a combi boiler does. They heat a cylinder, which needs a cupboard roughly the size of a traditional airing cupboard. If you have a combi now, finding that space is often the biggest practical question.
Where the outdoor unit goes
The outdoor unit needs free air around it, a solid base or wall bracket, and somewhere for water to drain, because it produces condensate and defrost water in winter. Modern units are quiet, but placement still matters: away from bedroom windows, yours and your neighbours’, and not boxed into a tight corner where sound bounces around.
Planning and permissions
In England, an air source heat pump on a house is often permitted development, so it does not need planning permission, as long as it stays within limits on size, position and noise. Scotland and Wales have their own rules.
Flats, listed buildings and homes in conservation areas may need planning permission, listed building consent or the freeholder’s agreement. We check what applies before we quote.