Heat Pumps in Old Houses: What UK Homeowners Need to Know in 2026
An air source heat pump can be installed in most old houses, including Victorian terraces, Edwardian semis, and stone cottages. Installation costs £9,000 to £13,000 before the £7,500 Boiler Upgrade Scheme grant, reducing your out-of-pocket cost to as little as £1,500. The key requirement is improving your home's insulation first, because old houses lose heat faster and force the heat pump to work harder. This guide covers insulation priorities, radiator upgrades, costs by house type, planning rules for listed buildings, and how to calculate whether a heat pump makes financial sense for your property.
Why old houses need extra preparation
Modern homes are built with cavity walls, double glazing, and loft insulation as standard. Old houses, typically anything built before 1930, were not. Solid stone or brick walls, single glazing, draughty floors, and minimal roof insulation mean heat escapes far faster. A 3-bedroom Victorian semi might have an annual heat demand of 16,000 to 20,000 kWh, compared to 11,500 to 13,000 kWh for a modern equivalent.
Heat pumps operate most efficiently at lower flow temperatures, typically 35 to 45 degrees Celsius rather than the 60 to 70 degrees a gas boiler produces. This works perfectly in a well-insulated home. In a draughty old house with undersized radiators, the heat pump must push harder and hotter, reducing its efficiency and increasing your electricity bills. That is why insulation comes first.
Use our heat pump cost calculator to estimate running costs based on your property type and insulation level.
Insulation priorities for old houses
You do not need to insulate everything before fitting a heat pump, but tackling the biggest heat losses first makes the system smaller, cheaper, and more efficient. Here is the order that delivers the best return.
1. Loft insulation
The cheapest and most impactful upgrade. If your old house has less than 100mm of loft insulation, topping up to 270mm saves a detached home around £355 per year. You can install loft insulation yourself for under £400, or get it free through the ECO4 scheme if you receive qualifying benefits. Check whether your existing loft insulation still works before adding more.
2. Solid wall insulation
Most old houses have solid walls, not cavity walls. Solid wall insulation is expensive but saves a detached home up to £590 per year on gas heating. External wall insulation wraps the building in a layer of rigid foam and render. Internal wall insulation uses insulated plasterboard on the inside face. External costs £8,000 to £22,000 for a detached house. Internal costs £4,000 to £14,000.
3. Draught-proofing
Old houses are full of uncontrolled air leaks through floorboards, sash windows, letterboxes, chimneys, and around door frames. Professional draught-proofing costs £200 to £400 and can cut heat loss by 10 to 15%. See recommended draught excluder strips for a DIY approach to the most common gaps.
4. Window upgrades
Replacing single glazing with double or secondary glazing reduces heat loss through windows by around 50%. Full double-glazing costs £4,000 to £8,000. Secondary glazing is cheaper at £1,000 to £3,000 and is often acceptable in conservation areas where replacement windows need planning approval.
Insulation first, heat pump second
Every pound you spend reducing heat loss means a smaller, cheaper heat pump and lower running costs for the next 20+ years. Use our insulation savings calculator to see exact figures for your property type.
Choosing the right heat pump for an old house
Air source heat pumps are the standard choice for old UK houses. Ground source systems deliver higher efficiency (COP of 4.0+ versus 2.6 to 3.2 for air source) but cost £15,000 to £35,000 and require significant garden space for boreholes or ground loops.
For an old house, the critical decision is heat pump sizing. An oversized unit wastes money on installation. An undersized unit runs constantly and never reaches comfortable temperatures. A qualified MCS installer will perform a full heat loss survey of your property before recommending a unit size. This survey accounts for wall construction, glazing type, insulation levels, room volumes, and your local climate.
Typical sizing for old houses after basic insulation upgrades:
| Property type | Estimated heat demand (kWh/yr) | Typical heat pump size |
|---|---|---|
| 2-bed Victorian terrace (insulated) | 10,000 to 12,000 | 6 to 8 kW |
| 3-bed Edwardian semi (insulated) | 14,000 to 16,000 | 8 to 10 kW |
| 3-bed detached cottage (insulated) | 16,000 to 18,000 | 10 to 12 kW |
| 4-bed detached Victorian (insulated) | 18,000 to 22,000 | 12 to 16 kW |
Estimates assume loft and wall insulation upgraded, double glazing. Uninsulated properties may need 30 to 50% larger units.
Compare the full cost breakdown by house type in our heat pump costs by house type guide.
Radiator upgrades: do you need them?
Probably, but not always. Heat pumps deliver water at 35 to 45 degrees rather than the 55 to 70 degrees from a gas boiler. Your existing radiators may not have enough surface area to heat each room at these lower temperatures.
An MCS installer will calculate the required radiator output for every room. In many old houses, you will need to replace some radiators with larger ones or add additional panels. Budget £2,000 to £4,000 for a full radiator upgrade in a 3-bed house. Underfloor heating works brilliantly with heat pumps but is disruptive and expensive to retrofit, costing £3,000 to £6,000 per floor.
Some rooms may already have oversized radiators, especially if the original Victorian or Edwardian units are still in place. Large cast iron radiators have substantial surface area and can work well with a heat pump without replacement.
Cost breakdown for a typical old house
Here is what a full heat pump retrofit looks like for a 3-bedroom Edwardian semi-detached with solid walls, currently on a gas boiler.
| Item | Cost range |
|---|---|
| Air source heat pump (10 kW, installed) | £9,000 to £12,000 |
| BUS grant deduction | -£7,500 |
| Radiator upgrades | £2,000 to £4,000 |
| Hot water cylinder (if needed) | £800 to £1,500 |
| Solid wall insulation (internal) | £5,000 to £9,000 |
| Loft insulation top-up | £300 to £600 |
| Draught-proofing | £200 to £400 |
| Total (after BUS grant) | £9,800 to £20,000 |
Costs based on 2026 market rates. BUS grant requires MCS-certified installer. Apply via GOV.UK.
If you are on a low income and receive certain benefits, you may qualify for ECO4 funding to cover some or all insulation costs, significantly reducing the total.
Running costs: heat pump vs gas boiler in an old house
At the Q1 2026 Ofgem price cap, electricity costs 24.5p/kWh and gas costs 6.76p/kWh. A heat pump with a COP of 2.9 delivers heat at an effective cost of 8.4p/kWh, which is higher than gas at 6.76p per kWh. The gap narrows significantly if you switch to a heat pump tariff.
Octopus Cosy, for example, offers cheaper electricity during off-peak hours specifically for heat pump users. Running your heat pump predominantly during off-peak windows can reduce your effective electricity cost to around 15 to 18p/kWh, bringing your heating cost per kWh closer to 5 to 6p. See our full comparison of heat pump electricity tariffs.
For a 3-bed Edwardian semi with 15,000 kWh annual heat demand:
| System | Annual heating cost |
|---|---|
| Gas boiler (90% efficiency) | £1,127 |
| Heat pump (COP 2.9, standard tariff) | £1,267 |
| Heat pump (COP 2.9, heat pump tariff) | £862 to £1,034 |
Based on Ofgem Q1 2026 price cap rates. Standing charges excluded. Heat pump tariff assumes 15 to 18p/kWh effective rate.
Read our detailed breakdown of heat pump running costs and use the boiler vs heat pump calculator for your specific property.
Planning permission and listed buildings
Most heat pump installations fall under permitted development and do not need planning permission. However, old houses often come with restrictions.
Listed buildings always require listed building consent for any external alteration, including mounting an air source heat pump on an exterior wall or placing one in the garden. Your local conservation officer will assess the visual impact. Internal alterations that affect the building's character also need consent.
Conservation areas restrict installations visible from a public road or footpath. You may be able to site the heat pump in a rear garden, behind a wall, or use an acoustic enclosure that reduces both noise and visual impact. See our full planning permission guide for details.
Noise limits apply everywhere. The planning limit is 42 dB measured at your nearest neighbour's window. Most modern air source heat pumps operate at 40 to 50 dB at 1 metre, dropping to well below 42 dB at typical boundary distances. See recommended anti-vibration pads to reduce transmitted noise further, and read our heat pump noise guide for practical reduction tips.
Listed building owners: apply for consent early
Listed building consent can take 8 to 12 weeks. Apply before ordering your heat pump to avoid delays. Your installer may have experience with similar properties and can advise on positioning that is more likely to gain approval.
Common concerns with heat pumps in old houses
Will it keep my house warm enough?
Yes, if the system is correctly designed. A properly sized heat pump with upgraded insulation and radiators will maintain 21 degrees throughout your home. The difference is that heat pumps deliver steady, consistent warmth rather than the rapid burst of heat from a gas boiler. Many owners of old houses report greater comfort because the temperature stays more even throughout the day.
What about hot water?
Heat pumps heat water to 50 to 55 degrees, which is sufficient for domestic use. You will need a hot water cylinder, typically 200 to 300 litres for a family home. If your old house currently has a combi boiler with no cylinder, you will need to find space for one. Most old houses originally had a cylinder anyway, and the original airing cupboard can often be reused.
Will it damage old walls or structure?
No. The heat pump unit sits outside, connected to the indoor system by two refrigerant pipes that pass through a small drilled hole in an external wall. This is less invasive than fitting a new gas boiler flue. Internal wall insulation does reduce room sizes slightly, by 50 to 100mm per treated wall.
Step-by-step: getting a heat pump in your old house
1. Assess your insulation. Check your current EPC rating and identify the biggest heat loss areas. Use our EPC improvement planner to prioritise upgrades.
2. Insulate first. Tackle loft, walls, and draught-proofing before committing to a heat pump. This reduces the required heat pump size and cost.
3. Get MCS installer quotes. Use the MCS certified installer directory to find local heat pump installers. Get at least three quotes. Each should include a full heat loss calculation.
4. Apply for the BUS grant. Your MCS installer applies on your behalf through GOV.UK. The £7,500 grant is deducted directly from your invoice. The scheme runs until April 2028.
5. Check for additional funding. If you are on a low income, check grant eligibility for ECO4 insulation funding. Council tax band reductions may apply after significant energy improvements.
6. Install and commission. A typical air source heat pump installation takes 2 to 3 days. The installer will commission the system, set up your controls, and walk you through operation. See recommended smart thermostats for optimal heat pump control.
Frequently asked questions
Can you fit a heat pump in a Victorian house?
Yes. Victorian houses work well with air source heat pumps once insulation is upgraded. Solid wall insulation, loft insulation, and larger radiators are the typical prerequisites. Use our heat pump calculator to estimate costs for your specific Victorian property after the £7,500 BUS grant.
Do you need to insulate before installing a heat pump?
You do not legally need to insulate first, but it is strongly recommended. A poorly insulated old house needs a much larger heat pump to reach comfortable temperatures, increasing both installation and running costs. Our insulation savings calculator shows you the return on insulating first.
Will a heat pump heat an old stone house?
Yes. Stone walls lose heat faster than modern cavity walls, so you will likely need internal or external wall insulation and may need to oversize the heat pump slightly. A well-designed system with upgraded radiators will heat a stone house effectively.
How much does a heat pump cost for an old house in the UK?
Air source heat pump installation in an old house typically costs £9,000 to £13,000 before the grant, reflecting the larger unit size often needed. The £7,500 BUS grant reduces this to roughly £1,500 to £5,500 out of pocket.
Do I need planning permission for a heat pump on a listed building?
Yes. Listed buildings require listed building consent for any external alteration including a heat pump. You may also need planning permission depending on the unit's location. Read our planning permission guide for the full process.
Data sources
Cost and performance data from Energy Saving Trust. Energy prices from Ofgem Q1 2026 price cap. BUS grant details from GOV.UK. Planning rules from GOV.UK permitted development guidance.