Guide: heat pumps
Is my house suitable for a heat pump?
Almost any house can be heated by a heat pump. The real question is whether yours can be heated well and affordably, and that is decided by heat loss, radiators, flow temperature and design quality rather than by the age of the building or the brand on the box.
Last reviewed: September 2026
What suitability actually means
A heat pump moves heat rather than burning fuel, and it does that most efficiently when it supplies water at a low temperature. A gas boiler might run radiators at a high flow temperature without much thought. A heat pump running at that temperature will work, but its efficiency, and therefore your running cost, will suffer.
So suitability is really a question about whether your house can be kept warm with lower temperature water. That depends on how quickly the house loses heat and how much surface area you have to put heat back in.
The five things that decide the answer
- 01Heat loss. A room-by-room heat loss calculation, not a rule of thumb based on floor area or the size of your existing boiler. This is the foundation of the whole design.
- 02Emitters. Radiator or underfloor surface area at the design flow temperature. Some rooms will usually need larger radiators, and the survey should say which ones.
- 03Flow temperature. The lower the design flow temperature, the better the efficiency. A design in the mid range is normal in a reasonably insulated house; a very high one is a warning sign.
- 04Insulation and draughts. Loft insulation, draughtproofing and obvious cold spots reduce heat loss cheaply and shrink the heat pump you need.
- 05Space and siting. Somewhere sensible outdoors for the unit, with airflow and attention to noise, and somewhere indoors for a hot water cylinder.
Hot water is a separate question
A heat pump with a combi-style instant hot water arrangement is unusual; most installations include a cylinder. That needs floor space or a cupboard, and it changes how the system is controlled. If you currently have a combi boiler and no cylinder, finding the space is part of the suitability question, not an afterthought.
Ask how hot water will be produced, at what temperature, how often, and what that adds to annual running cost. Ask about legionella protection cycles and how they are scheduled.
What a proper survey looks like
- A room-by-room heat loss calculation, provided to you as a document rather than described verbally.
- A stated design flow temperature and a stated outside design temperature.
- A schedule of which emitters are being kept, upsized or replaced, with those costs in the quote.
- A pipework assessment, since some existing pipe runs limit flow rates.
- A sizing conclusion that follows from the heat loss figure, not from the rating of your old boiler.
- A noise assessment for the outdoor unit position and a check of permitted development requirements.
- A predicted seasonal efficiency figure, with an explanation of what it means at your electricity price.
Running costs: the honest position
We do not publish a blanket savings claim, because the answer depends on what you are replacing. Households moving from oil, LPG or direct electric heating frequently see lower running costs. Households moving from an efficient mains gas boiler are moving from a cheaper fuel to a more expensive one per unit, and whether that comes out ahead depends on the efficiency the system actually achieves and on the tariff you are on.
That is why design quality matters more than brand. A well designed system at a low flow temperature on a suitable tariff is a different financial proposition from the same equipment installed badly.
Common mistakes
- Sizing the heat pump from the old boiler rating, which is almost always oversized for the house.
- Keeping every existing radiator and quietly raising the flow temperature to compensate.
- Skipping cheap insulation and draughtproofing, then paying for a larger unit than necessary.
- Running the system in short bursts like a gas boiler rather than steadily at a lower temperature.
- Choosing the cheapest quote when the difference is the heat loss survey and the radiator schedule.
- Assuming the grant decides the question. A grant changes the price, not whether the design suits the house.
Questions to ask an installer
- 01Can I see the room-by-room heat loss calculation for my house?
- 02What design flow temperature are you targeting, and at what outside temperature?
- 03Which radiators need changing, and is that cost inside this quote?
- 04What seasonal efficiency do you predict, and what does that mean in pounds at my tariff?
- 05Where will the outdoor unit and the cylinder go, and what noise assessment applies?
- 06Are you MCS certified and registered to claim the relevant grant, and is this quote net of it?
- 07What insulation or draughtproofing would you do first if this were your own house?
A reasonable order of work
- 1. Fix the cheap things first: loft insulation, draughtproofing, obvious cold spots.
- 2. Get a heat loss survey from an installer who will hand you the calculation.
- 3. Compare quotes on design and emitter schedule, not just on price.
- 4. Check the grant position in writing before paying a deposit.
- 5. Review your electricity tariff, since it becomes your main heating cost.
Your electricity price becomes the number that matters
A heat pump makes your home more dependent on electricity. The solar calculator is the quickest way to see what cheaper daytime electricity would be worth to you.