Are heat pumps worth it in older Dorset homes?

Yes, a heat pump can be worth it in many older Dorset homes, but only if it is designed properly for the house. Stone cottages, Victorian terraces and even thatched homes can be heated well by a heat pump when the system is sized from a proper heat loss survey, the radiators are right and the obvious draughts are sorted first. If you heat with oil or LPG, typical savings are £200 to £600 a year against oil and £400 to £1,000 a year against LPG. Against mains gas the gain is smaller and less certain.

This guide gives you the honest picture, including when a heat pump is not the best choice.

Why older homes are different

Dorset has a lot of older housing: Portland stone cottages, Purbeck stone villages, brick and flint farmhouses, cob and thatch in the west of the county, and streets of Victorian terraces in towns like Weymouth, Bournemouth and Bridport. Many of these homes have solid walls rather than cavity walls, which means they lose heat faster.

That does not rule out a heat pump. It means the design has to account for it. A home built before 1919 typically needs around 1.35 times the heat of a similar home built between 1965 and 1999. A good installer plans for that rather than guessing.

Start with a proper heat loss survey

The single most important step is a room by room heat loss calculation. The installer measures each room, notes the walls, windows, floors and ceilings, and works out how much heat each room needs on a cold day. That tells them:

• what size heat pump you need
• whether each radiator is big enough
• what flow temperature the system can run at

An installer who sizes a heat pump from your old boiler’s size, or from a quick look round, is a red flag. Our guide on how to choose an MCS installer explains what a good survey looks like.

Flow temperatures and radiators

Old boilers often send water round the radiators at a high temperature. Heat pumps work most efficiently at lower temperatures, which means a radiator gives out less heat at any one time. To keep rooms just as warm, some radiators may need to be larger.

A well designed system typically reaches a seasonal efficiency (SCOP) of around 3 or higher, meaning it delivers about that many units of heat for every unit of electricity. Running at a higher flow temperature to avoid changing radiators lowers that efficiency and raises your bills.

In older homes, radiator upgrades are common. Where they are needed, expect around £1,000 to £3,500. Often only a few rooms need changing, usually the ones with the most outside wall or the largest windows. Your existing pipework may also need checking, especially narrow microbore pipes.

Insulation and draught proofing first

The cheapest heat is the heat you do not lose. Before or alongside a heat pump, look at:

• Loft insulation, topping it up if it is thin
• Draught proofing around doors, sash windows, floorboards and unused chimneys
• Floor insulation where suspended timber floors are easy to reach
• Secondary glazing, which can work well in listed or conservation area homes where replacement windows are not allowed

Solid wall insulation is more involved and needs care in older buildings, which need to breathe. Get specialist advice before fitting internal or external wall insulation to stone, cob or lime built walls. If your household is on a lower income, ask Dorset Council or BCP Council about ECO4, the Great British Insulation Scheme or a Warm Homes: Local Grant.

Running costs against oil, LPG and gas

A heat pump runs on electricity. Many households switch to a heat pump tariff, with an average rate of around 20p per kWh, compared with a standard rate of about 26p per kWh. With a typical old boiler at around 85% efficiency, here is how it tends to compare:

• Oil (around 7p per kWh): typical saving of £200 to £600 a year
• LPG (around 9p per kWh): typical saving of £400 to £1,000 a year
• Mains gas (around 6.5p per kWh): typically -£100 to £250 a year, so it may cost a little more or a little less

These are typical ranges, not promises. A careful design, a good tariff and sensible controls make the biggest difference. Pairing the heat pump with solar panels can help further. For a rough figure for your home, try our heat pump estimate.

When a heat pump is a good fit

• You currently heat with oil or LPG, common in rural Dorset villages off the gas grid
• You can sort the main draughts and top up loft insulation
• You have room outside for the unit, away from bedroom windows where possible
• You have, or can fit, space for a hot water cylinder
• You are happy for the heating to run steadily at a lower temperature rather than blasting on and off

When it may not be the right choice yet

• The house is very draughty and you cannot address it soon
• There is nowhere suitable for the outdoor unit, for example a mid terrace with no rear access or garden
• You are on mains gas, have a newish efficient boiler and want a guaranteed saving
• Major renovation is planned. It is usually better to do insulation and building work first, then design the heat pump around the finished home

Being told “not yet” by an honest installer is a good sign.

Listed buildings, conservation areas and thatch

Most air source heat pumps on houses are permitted development, but listed buildings need listed building consent for the outdoor unit and often for internal changes such as new pipework. Conservation areas, such as the historic centres of Dorchester or Shaftesbury, can have extra rules about where the unit goes, especially if it is visible from the road. Your installer will check with the council.

Thatched homes can often have a heat pump, and removing an oil or LPG boiler and flue can be appealing for some owners. The outdoor unit should be placed sensibly and the installer should talk through any insurance requirements with you.

The Boiler Upgrade Scheme gives £7,500 towards the cost. Read the Boiler Upgrade Scheme explained for eligibility, and see more about air source heat pumps in Dorset. If payment comes up, ask your installer about payment options.

Next steps

Get a rough cost and running cost with our free heat pump estimate. Then request quotes and we will pass your details to up to 3 local MCS certified installers, who will carry out a proper heat loss survey before recommending anything.