Thinking about a heat pump this winter? The electrical question your installer might gloss over

Most of the heat-pump conversations I get pulled into start the same way: the heating quote's on the kitchen table, it all looks sorted, and then someone crouches down at the meter with me and we look at the main fuse together. It's the fat ceramic carrier where the supply comes into the house... and on a lot of the older places round here it's stamped 60 or 80, not 100. That little number is the one the glossy heat-pump quote didn't mention, and now and again it's the difference between "yes, straightforward" and "hang on, we need to sort the supply first."

I'm not the one selling you the heat pump, so I've no axe to grind either way. But the electrics are the part heating installers tend to skate over, and it's the part that trips jobs up late. So here's what actually needs checking before you commit.

A heat pump wants its own circuit

An air-source heat pump isn't a plug-in appliance. It needs its own dedicated circuit run from your consumer unit (its own protective device, correctly sized to the unit) not a spur off something else and definitely not an extension lead's worth of thinking.

Which raises the first practical question I get asked to answer: is there room? On a house that's had a modern board fitted, usually yes. On a house still running an older or full consumer unit, there may be no spare way to add the circuit, and that's a job in itself before the heat pump even arrives. It's the same reason I bang on about the board with EV chargers... any big new load starts at the fuse box, and the fuse box has to have room for it.

The network has to be told... and sometimes asked first

Here's the bit homeowners rarely know about. Your Distribution Network Operator (the company that owns the cables and the main fuse in the street, not your energy supplier) generally has to be informed when you add a big load like a heat pump.

For a lot of installs that's a straightforward notification. For others, where the extra demand is larger relative to your existing supply, it has to be an application that's assessed and approved before the thing is connected. Which of those applies depends on your particular house (your existing load, your supply, and what else you're running) and it's your installer and the network operator who work that out between them. The reason I flag it is simple: it can add time, and it's better known about at the quoting stage than discovered the week of the install.

Why the main fuse matters

This is where the older housing stock round Slough, Burnham and Farnham Common comes in. Plenty of it is still on a 60 or 80 amp main service fuse... fine for how the house has always been used, but a heat pump is a meaningful new load stacked on top of everything else. If your existing demand plus the heat pump pushes past what that supply comfortably allows, you're into a supply upgrade before you're into a heat pump.

One important thing to be clear on: that main fuse and the cutout are the network's property, not mine and not yours. Nobody should be pulling or swapping it off their own bat. If the supply needs uprating, say from 60 to 100 amp, that's requested from the network operator through the proper channel. What I can do is look at your board and your existing arrangement and tell you honestly whether capacity is likely to be your problem, so you go into the heat-pump quote with your eyes open.

What about the grant?

Money's usually the reason people are looking at all this now, and there's a government grant toward a heat pump through the Boiler Upgrade Scheme. As it stands that's £7,500 off an air-source heat pump, and from 21 July 2026 it goes up to £9,000 for off-gas-grid homes coming off oil or LPG. Those figures do get reviewed, though, so treat them as the starting point and check the current Boiler Upgrade Scheme amount on GOV.UK before you budget. What I'd add from the electrical side is that the grant is toward the heat pump itself... any board upgrade or supply work your particular house needs sits outside that, which is exactly why it's worth knowing about early rather than as a surprise.

Getting the electrics straight before you commit

I can't tell you your spare capacity or whether your supply will cope down the phone... I'd want to see the board and the incomer. But that look is quick, and it's a lot cheaper than finding out mid-install. I'm a NAPIT-registered electrician based in Slough, covering Burnham, Windsor, Maidenhead and across the Thames Valley, and I'll tell you straight where you stand on the circuit, the board and the supply before you sign anything. For a free, no-obligation quote, or just a sanity-check on your consumer unit and supply ahead of a heat pump, get in touch.