Heat Pump in an Older Home: Victorian, 1930s & 1950s Houses

Estimate the Saving for Your Old House

Heat Pumps in Old Houses: What You Need to Know

Installing a heat pump in an older property is absolutely achievable, but it takes more planning, a bigger budget, and often some insulation work before the heat pump goes in. The good news is that insulation upgrades and a heat pump, with the grants available, can bring the running costs of even a draughty Victorian terrace below gas, if the install is good. Here's what to expect by property era.

Heat Loss by Era: How Old is Your House?

The older your home, the higher its heat loss is likely to be, and heat loss drives everything else: how big a heat pump you need, how your radiators perform, and what you'll pay to run the system. Here are rough annual heat demands for common UK property eras, before any insulation improvements (our rough guide, not a measurement of your house):

Compare this to a modern home built to current standards, which we'd expect to need something like 5,000 to 8,000 kWh a year. The gap is significant, but insulation works can close much of it.

Insulate First: The Priority Order

Before installing a heat pump in an older property, we'd tackle insulation in this order. Each step reduces heat demand, potentially allowing a smaller heat pump unit and improving running efficiency:

1. Loft Insulation

One of the most cost-effective upgrades. The Energy Saving Trust says an uninsulated home loses around 25% of its heat through the roof. It puts installed loft insulation at £750 in Great Britain to take an empty loft to the recommended 270mm, or £600 to top up from 120mm (£1,100 and £700 respectively in Northern Ireland). It's worth doing whether or not a heat pump follows.

2. Cavity or Solid Wall Insulation

For homes with an unfilled cavity (from about the 1920s and 1930s on), cavity wall insulation is the next easiest job. The Energy Saving Trust's figure for a typical GB home is around £2,200 (around £1,000 in Northern Ireland). It involves drilling small holes in the external mortar and injecting insulation; the holes are then filled and become hard to spot.

For Victorian properties with solid walls, this gets expensive fast, and it's where "insulate first" stops being cheap. The Energy Saving Trust's figures for a typical three-bed semi are around £12,000 for internal wall insulation and around £15,000 for external. External insulation doesn't take any room space, but it changes the look of the building, so check with your council first, especially in a conservation area. Internal insulation slightly reduces the floor area of each room it goes in, which you'll notice in a narrow terrace room. It can be done room by room, which is one way to afford it: doing the two coldest rooms costs a fraction of the whole-house price.

Be honest with yourself about this line. If £12,000 of wall insulation isn't happening, that's fine, but plan the heat pump around the heat loss you'll actually have rather than the one you'd have after works you're not going to do. Grants may be available through ECO4 (Great Britain) or the Warm Homes: Local Grant (England) for eligible households (ECO4 runs to 31 December 2026).

3. Draught Proofing

Old houses leak air through floorboards, window frames, skirting boards and loft hatches. The Energy Saving Trust puts professional draught proofing of windows and doors at around £250 for a whole house, and the saving from draught proofing at about £55 a year in Great Britain. A chimney cap starts at around £150, and draught proofing an open chimney you don't use saves around £45 a year. DIY is cheaper still. It's cheap, and it should happen alongside any heat pump installation.

What Insulation Does to Your Heat Demand

A typical Victorian terrace with solid walls, poor loft insulation and single glazing might need something like 18,000 kWh of space heating a year. After adding loft insulation, better glazing and draught proofing (even without wall insulation), we'd expect the space heating to drop to something like 10,000 to 12,000 kWh (before hot water). That makes a big difference to heat pump sizing and running costs.

Heat Pump Sizing for Old Properties

Run through our size calculator's model (the same RdSAP-based method as the calculator below, our example homes), the cheaper insulation work changes the size of heat pump you need far more than the age of the house does:

That's why sizing from the survey after the insulation work matters: a heat pump picked for the draughty house would be oversized for the insulated one, costing more to buy and cycling on and off in mild weather. A bigger period house is a different story: our model puts a 140 sq m Victorian semi with solid walls and an open chimney at about 9.9kW, so a 10kW unit. A proper heat loss survey calculates the actual figure for your home.

Radiators: Budget for Upsizing

A heat pump runs at a lower flow temperature than a gas boiler, typically 35C to 55C against 70C to 80C (British Gas's figures), so each radiator gives out less heat. The higher a room's heat loss, the more likely its radiator is too small at heat pump temperatures, so an older house tends to need more of them changed.

On our estimates, upsizing 7 to 12 radiators through a larger or poorly insulated older house comes to about £1,050 to £4,800. Ground-floor underfloor heating is worth considering if you're lifting floors anyway, because it works at low flow temperatures. Your installer's room-by-room heat loss calculation says exactly which rooms need what; our radiator guide explains how to check yours.

Running Costs: A Victorian House After the Work

Take an insulated Victorian that needs 12,000 to 14,000 kWh of heat a year including hot water. That's our example range, not a measurement of your house. We've used a SCOP of 3.2 rather than 3.5, because a solid-wall house usually needs a higher flow temperature and runs a little less efficiently for it.

So the heat pump comes out roughly £180 to £200 a year cheaper, before any heat pump tariff. Rates are the 1 October to 31 December 2026 price cap. A Victorian sits closer to the 2.97 break-even than a modern house, which is why commissioning matters so much here: set it up badly at 55C flow and you can land on the wrong side of that line. A heat pump tariff widens the gap.

Listed Buildings and Conservation Areas

If your older property is listed or sits in a conservation area, you face additional constraints:

• Any wall insulation that affects a listed building's character needs listed building consent, inside or out
• In England, permitted development doesn't apply within the curtilage of a listed building, so the outdoor unit needs planning permission, and listed building consent for any works that affect the building's character
• In England, in a conservation area, permitted development still applies, but the unit can't go on a wall or roof that fronts a highway, or nearer a highway than the house

Always talk to your local planning authority before you go ahead. Ask your council about pre-application advice, and start with the least visible spot for the unit.

Realistic Total Costs for an Old House

Those Victorian numbers are uncomfortable, and they're the reason we'd steer most solid-wall owners away from the full-retrofit version. Loft insulation, draught proofing and a correctly sized heat pump come to roughly £12,500 before the grant and £5,000 after it, plus whatever radiators the survey says you need, and that gets you most of the way. That's for the 5kW heat pump our example needs once it also has double glazing and a capped chimney, which we haven't costed here, with the EST's loft figure for a semi. The £12,000 of internal wall insulation buys real comfort, but it's unlikely to pay back on fuel savings alone, so do it because you want warm walls, not because a payback calculator told you to.

A 1930s semi that just needs cavity fill sits at the lower end. A Victorian end-terrace doing everything sits at the top. Check what you're eligible for before committing to any of it.

Is It Worth It?

Yes, with a condition attached, and in an old house the condition matters more than anywhere else. At the 1 October to 31 December 2026 price cap, a heat pump at SCOP 3.5 delivers heat at 7.5p per kWh against 8.9p from a 90% gas boiler, so it's about 15% cheaper to run. At the SCOP of 3.2 we allow for an old house, it's about 8.2p a kWh, about 7% cheaper. Break-even is a SCOP of 2.97. An old house with high heat loss pushes flow temperatures up and SCOP down, which is exactly how you end up on the wrong side of that line and paying more than you did on gas.

That's why the insulation order of works above isn't optional advice in a period property, even though it's no longer a condition of the grant. Every degree you take off the design flow temperature helps, and in a solid-wall house the difference between 55C and 45C can be the difference between saving money and not.

Start with a professional heat loss survey. You don't need an EPC. The Boiler Upgrade Scheme (Amendment) Regulations 2026 (SI 2026/390) came into force on 28 April 2026 and deleted the requirement for an eligible property to have a valid EPC. The condition to clear insulation recommendations first had already gone on 8 May 2024. Don't let anyone charge you for an EPC on the basis that the grant needs one. Our heat pump grants guide covers every funding source currently available for older properties.