Home Charging
EV Charger and Heat Pump on One Supply: Load Management Guide
How EV charger heat pump load management works: CT-clamp curtailment, 60/80/100A main fuse ratings, when DNO fuse upgrades are free and when you need more supply.
By Evova · Published
Yes — an EV charger and a heat pump can share a standard single-phase supply in almost every UK home, and adding an electric shower or a hot tub to the mix rarely changes that. The trick is load management: a CT clamp on your meter tails watches the whole house’s demand and turns the charger down whenever the total approaches your main fuse rating, then back up afterwards. Genuine supply upgrades are the exception, and the installer you choose will check your supply and consumer unit as part of the quote — find an installer near you or request a free quote.
What load management actually does
A CT (current transformer) clamp is a small sensor clipped around your incoming supply cable. It measures the total current your home is drawing at any moment, and the charger reads that figure continuously. If the oven, shower and heat pump push the house towards the fuse limit, the charger throttles down — sometimes to a trickle — then restores full power once the peak passes. Nothing trips, and nobody has to think about it.
There’s a regulatory reason this matters. IET guidance on BS 7671 (the wiring regulations) says no diversity may be applied to an EV charging circuit when assessing a home’s maximum demand — and installers typically treat a dedicated heat pump circuit the same way — so the paper figure assumes everything runs flat out at once, which inflates it fast. The same guidance accepts CT-based load curtailment as a legitimate way to keep total demand within the supply rating, which is why most modern home chargers are designed to work with one. The same clamp is also what enables solar surplus charging, if you have panels.
How much room is on your main fuse?
Most UK homes are fed through a sealed service fuse — the cut-out — rated at 60A, 80A or 100A, though a few older supplies are lower still. At 230V, that works out roughly as follows (simple amps-times-volts arithmetic, last checked July 2026):
| Main fuse | Approximate total capacity | Typical context |
|---|---|---|
| 60A | ~14kW | Common on older supplies |
| 80A | ~18.4kW | Frequent upgrade target |
| 100A | ~23kW | Standard on newer supplies |
Against that, a 7kW charger draws about 32A — roughly half of a 60A supply on its own. Electric showers run 7.5kW to 10.5kW, or about 33-46A while the water is on. Hot tubs split into 13A plug-in models and hard-wired ones on a dedicated 32A (sometimes 40A) circuit. A heat pump typically sits on a dedicated circuit of 16A for a small unit, up to 32A or more for larger ones — though its running draw is usually well below the circuit rating, because a heat pump delivers several units of heat per unit of electricity.
One caution: don’t open the cut-out to read your fuse rating yourself. It’s the DNO’s property and sealed — your installer or the DNO can confirm what’s fitted.
Fuse upgrades: often free, usually triggered for you
Fuse upgrades are done by your DNO — the regional company that owns the cables — not your energy supplier. Whether it costs anything varies. UK Power Networks upgrades cut-out fuses to 80A or 100A free of charge, offers a free site visit it aims to arrange within 15 working days, and for EV and heat pump customers asks the installer to apply for the device first — it says there’s no need to request a fuse upgrade yourself. National Grid Electricity Distribution upgrades 30A or 60A fuses to 80A, but says any cost depends on the specifics of the application (both last checked July 2026). In short: often free where the network allows, but not a blanket rule.
The main complication is a looped supply — one service cable feeding two neighbouring homes, common in some older estates and terraces. Unlooping has to be planned with your neighbour’s household too, and some shared-cable cases can involve a charge. The DNO arranges it; allow extra lead time.
Why the survey asks about your shower, hob and hot tub
Because the paperwork demands it. The industry-standard ENA connections process for EV chargers and heat pumps requires a load survey of the whole premises to calculate maximum demand — it asks about existing chargers, electric heating, battery storage, solar and any other large loads, and whether a load-limiting device is fitted. If the criteria are met, the installer can connect and notify the DNO within 28 days; if the new maximum demand exceeds 60A per phase or your cut-out rating, the installer must apply and get the DNO’s confirmation before installation. Declaring the CT-clamp system is what keeps most homes on the fast connect-and-notify route — though it isn’t treated as a free pass, partly because curtailment reacts with a short time-lag rather than instantly.
When is a supply upgrade genuinely needed?
Rarely, for a 7kW charger plus a heat pump. The cases that do justify one: maximum demand still above the cut-out even with curtailment declared, two chargers without shared load management, or wanting 22kW charging — which needs three phases. Three-phase conversion costs vary enormously, from modest sums where the local network is ready to five-figure bills where new cabling or reinforcement is needed; each DNO prices jobs through its own estimator, so get a real quote rather than trusting a blog figure. And if you rent or own a flat, the EV chargepoint grant can still take up to £500 off the socket itself.
DNO policies, notification thresholds and grant rules all move over time — the ENA connections form and your own DNO’s website are the operative sources, and a good installer deals with both daily. For the broader picture, start with our home charging hub, or request a free quote and let the survey answer the fuse question for you.