Heat pumps

IN THIS GUIDE

How a heat pump works

An air source heat pump works like a fridge in reverse: it extracts heat from the outside air — even in winter — and concentrates it to warm your home and hot water. Because it moves heat rather than burning fuel, it delivers 3–4 units of heat per unit of electricity (a ‘COP’ of 3–4), which is why it can be cheaper to run than gas despite electricity costing more per unit.

It runs at lower flow temperatures than a gas boiler (typically 35–50°C vs 65–75°C), heating your home more gently and steadily. That is why sizing, insulation and radiators matter more than they do with a boiler.

What a heat pump costs

A typical air source install is £8,000–£14,000 before grants, depending on your home’s size and how much pipework and radiator work is needed. The £7,500 Boiler Upgrade Scheme grant comes straight off that, so most households pay £1,500–£7,000 net. Ground source pumps cost more (£18,000–£35,000) but run more efficiently. Use the calculator below for a figure for your home.

What size (kW) you need

Heat pumps are sized to match your home’s heat loss, not its floor area. As a rough guide a well-insulated 3-bed needs around 5–8 kW; a larger or draughtier home 10–16 kW. Oversizing wastes money and cycles inefficiently; undersizing leaves you cold in a cold snap. A proper MCS heat-loss survey is the only way to size it correctly.

Running costs vs gas

With a COP of ~3.5 and a sensible tariff, a heat pump typically costs a little less to a little more than gas — the gap depends heavily on your electricity tariff and how well the system is set up. A heat-pump tariff with cheaper off-peak rates, plus good insulation, is what tips it clearly in your favour. Systems run too hot are the main reason some people see high bills.

Is your home ready?

A heat pump runs best in a home that holds its heat. Before installing it is worth insulating the loft and any cavity walls, draughtproofing, and checking whether a few radiators need upsizing to work at lower temperatures. You don’t need a perfect home — many Victorian houses run heat pumps well — but the basics pay off in comfort and bills.

Grants you can claim

The main one is the Boiler Upgrade Scheme (£7,500) in England & Wales, applied for by your installer. Scotland has Home Energy Scotland grants up to £7,500 (£9,000 rural) plus interest-free loans. Lower-income households may qualify for ECO4. See the grants guide.

Choosing an installer

Use an MCS-certified installer — required for the grant, and it means the system is designed and sized to standard. Get 2–3 quotes, ask to see the heat-loss calculation (not a rule of thumb), and check they will commission it to run at a low flow temperature. When you’re ready, we can connect you to vetted local installers.