What Electrical Supply Does a Heat Pump Need?

A domestic air source heat pump needs its own dedicated circuit from the consumer unit, usually protected by a 16 A to 32 A breaker depending on its size, plus a local isolator by the outdoor unit. Most homes with a 60 A, 80 A or 100 A main fuse can take one without a supply upgrade.

The deciding figure is your home’s new maximum demand. Your installer works it out, then tells the network operator (DNO). If the new demand is above 60 A, they must apply and get approval before connecting. This guide covers the circuit, the consumer unit, the main fuse, the DNO process and the regulations, plus what changes when you add an EV charger, solar panels or a battery.

How Much Electricity Does a Heat Pump Draw?

Manufacturer data for common 3.5 kW to 12 kW air source heat pumps shows maximum currents of about 14 A to 28 A on a single-phase supply, which calls for a 16 A to 32 A protective device. The running draw is usually well below that maximum.

A heat pump’s electrical input is its heat output divided by its efficiency at that moment. For example, a heat pump delivering 8 kW of heat at an efficiency of 3 draws about 2.7 kW. Mitsubishi rates its 8.5 kW Ecodan at 2.60 kW input at 7°C outside with 35°C flow water. The table shows published figures for a few popular single-phase models.

The hot water cylinder adds its own load. Most heat pump cylinders carry an immersion heater for backup and legionella cycles, and a typical element is 3 kW. Grant’s heat pump cylinder, for instance, uses a 3 kW immersion wired through a double pole isolator of at least 13 A.

Does a Heat Pump Need Its Own Circuit?

Yes, the outdoor unit goes on its own dedicated circuit from the consumer unit, rated to the manufacturer’s stated fuse or breaker size, with an isolator next to the unit so an engineer can safely switch it off for maintenance. It should not share a circuit with other appliances.

The electrician sizes the cable for the circuit rating, the length of the run and how it is installed, then checks voltage drop and fault loop readings. Manufacturers make the same point: Mitsubishi’s data sheets say its fuse ratings are guidance only and cable must be sized to current regulations and site conditions. The immersion heater and the indoor controls usually get their own supplies, so a typical job adds one or two new circuits.

Will My Consumer Unit Need Upgrading?

Often not, provided the consumer unit has a spare way and suitable RCD protection for the new circuit. Older fuse boxes with rewireable fuses, no RCDs or no room for another circuit usually need replacing.

The type of RCD matters with heat pumps. Their inverter drives can leak DC current, which can stop a standard RCD from tripping properly. BS 7671 regulation 531.3.3 covers choosing an RCD that works with DC components, and regulation 134.1.1 requires the installer to follow the manufacturer’s instructions. Depending on the model, that can mean a Type A, Type F or Type B device. Many electricians fit the heat pump on its own RCBO so a fault on that circuit does not trip anything else in the house.

What Main Fuse Size Does a Heat Pump Need?

Most heat pumps can run on a 60 A main fuse, but the real test is whether your existing load plus the heat pump pushes maximum demand above the fuse rating. The main fuse sits in the sealed cut-out next to your meter, and its rating is often printed on it.

If the fuse is too small, the DNO can upgrade it. UK Power Networks, for example, upgrades 30 A or 60 A fuses to 80 A or 100 A. Large heat pumps or homes with very high demand may need a three-phase supply, but that is uncommon for a typical house.

Do I Need to Tell the DNO About My Heat Pump?

Yes, every heat pump must be reported to the DNO: if the new maximum demand is 60 A or less and the other criteria are met, the installer can connect and notify within 28 days, but if it falls between 60 A and 100 A they must apply and get approval before installing. Both routes use the Energy Networks Association (ENA) form for heat pumps and EV chargers.

The form also asks for the earthing arrangement and the heat pump’s compliance with the power quality standards for harmonics and flicker. Many models are already listed in the ENA’s device database, which speeds this up.

Who Submits the DNO Application?

Your installer submits it on your behalf, normally through the ENA’s Connect Direct platform. MCS publishes guidance for its certified installers on notifying DNOs, and the form is part of our paperwork on every job. In Northern Ireland, NIE Networks adopted Connect Direct for heat pumps and EV chargers in August 2024.

How Long Does DNO Approval Take?

For an apply-to-connect case between 60 A and 100 A, the DNO confirms within 10 working days whether the heat pump can be connected. If a fuse upgrade or other work is needed, add time for a site visit. UK Power Networks, for example, aims to contact you within 10 working days to book one. We submit early in the process so any upgrade is booked before installation week.

What Happens If My Home Has a Looped Supply?

A looped supply, where your home shares a service cable with a neighbour, rules out connect and notify, so the installer must apply to the DNO, which may need to split the supply before the heat pump goes in.

The cost position has improved. Since 1 April 2023, Ofgem’s reforms mean demand customers no longer pay towards upstream network reinforcement, although they can still be charged for work at their point of connection. The ENA says GB network operators will provide what a home needs to decarbonise for free, up to a 23 kVA cable. UK Power Networks notes that work on a looped supply involves both households and may carry a charge, so ask your DNO to confirm costs in writing before work starts.

What Regulations Cover the Electrical Work?

All the wiring must meet BS 7671, the IET Wiring Regulations, and in England and Wales a new heat pump circuit is notifiable building work under Part P. The current edition is BS 7671:2018 with Amendment 4 (2026), published on 15 April 2026. The previous version is withdrawn on 15 October 2026.

An electrician registered with a competent person scheme can self-certify Part P work. You should receive an Electrical Installation Certificate, and the scheme notifies building control. If the electrician is not registered, the work must be inspected and certified by building control instead. In Wales, the Part P special locations also include kitchens and outdoor areas. Scotland and Northern Ireland have their own building standards, but BS 7671 still sets the wiring requirements across the UK.

Does a Heat Pump Need Special Earthing?

No special earthing is needed in most homes, but the electrician must identify your earthing arrangement and confirm it is safe before connecting. The DNO form asks whether the supply is TN-C-S, TN-S or TT.

With TN-C-S (often called PME) and TN-S, the earth comes from the network. With TT, found mainly in rural homes, the earth is a rod in the ground, which makes correct RCD protection essential. The electrician also checks main protective bonding to the incoming gas and water pipes, as the heat pump will be connected to both the electrical and plumbing systems. If bonding is missing, adding it is typically a few hours’ work.

Do I Need a Smart Meter or a Special Tariff?

A heat pump works with any electricity meter, but you need a smart meter to join a time-of-use tariff. Some suppliers offer tariffs with cheaper periods designed around heat pumps, and a smart meter provides the half-hourly readings those tariffs rely on.

If you still have an older Economy 7 meter that uses the Radio Teleswitch Service, ask your supplier to replace it. The RTS switch-off began on 30 June 2025, and the replacement is free.

Can a Heat Pump Share the Supply With an EV Charger, Solar Panels and a Battery?

Yes, but the installer must add every load into the maximum demand calculation, and a heat pump plus a 7.4 kW EV charger often pushes demand above 60 A, which triggers a DNO application or calls for load management. A 7.4 kW charger alone draws about 32 A at 230 V.

Load management usually means a current clamp on the incoming supply that tells the EV charger to slow down when other loads rise, then speed up again when they fall. It manages the existing supply rather than increasing it, which can avoid a fuse upgrade.

Solar panels and batteries generate rather than consume, and they follow their own DNO process. Systems up to 16 A per phase fall under G98, and the DNO must be notified within 28 days of commissioning. Larger systems, including many solar and battery combinations, fall under G99 and need approval before installation. If you plan to add all of these over time, tell your installer at the start. Designing the supply once is cheaper than revisiting it for each new device.

How Much Do Electrical Upgrades for a Heat Pump Cost?

Many heat pump installations need no electrical upgrade beyond the new circuits included in the quote, but a replacement consumer unit averages around £485 and main earth bonding costs £65 to £230. The figures below are national averages from Checkatrade’s 2026 cost guides and the DNO’s own guidance, and your quote may differ.

Our surveyors check the consumer unit, cut-out, earthing and existing loads during the home visit, so any electrical work shows up in your quote rather than on installation day.