Do Heat Pumps Need Three-Phase Power?

Quick Answer:

No.95% of UK homes have single-phase power, and that's perfectly adequate for residential heat pumps up to 16 kW.

Three-phase is only needed for very large homes (5+ bedrooms) or commercial properties.

What Most UK Homes Have

Single-Phase Power (Standard)

  • ✓95% of UK homes
  • ✓240V supply
  • ✓100A main fuse (typical)
  • ✓Can run heat pumps up to 16 kW

How to Check Your Supply:

Look at your main fuse (near your meter). If you see ONE main cable, you have single-phase. Three cables = three-phase (rare in homes).

Heat Pump Power Requirements

Heat Pump SizeTypical HomePeak Power DrawSingle-Phase OK?
5-6 kW2-3 bed semi2-3 kW electric✓ Yes
8-10 kW3-4 bed detached3-4 kW electric✓ Yes
12-14 kW4-5 bed large house4-6 kW electric✓ Yes
16+ kW5+ bed / commercial7+ kW electric⚠ Maybe

Note: Heat pumps use 3-4x LESS electricity than the heat they produce. A 10 kW heat pump only draws ~3 kW from the grid.

When You Actually Need Three-Phase

Rare Scenarios:

  • •Very large homes (5+ bedrooms, 300+ sqm)
  • •Commercial properties (offices, workshops)
  • •Multiple heat pumps on one property
  • •Your main fuse is under 60A (very old properties)

Cost to Upgrade:

Three-phase connection from DNO: £2,000-£5,000+. Usually cheaper to right-size the heat pump instead.

Electrical Work Included in Installation

Standard heat pump installation on single-phase includes:

  • ✓
    Dedicated circuit from consumer unit

    Usually 20-32A circuit breaker

  • ✓
    RCD protection

    Safety requirement

  • ✓
    Armoured cable to outdoor unit

    Weatherproof connection

  • ✓
    Electrical certification

    Required for building regs & BUS grant

Typical Electrical Cost:

£200-£500 (included in installation quote). Already factored into typical £8k-£14k total cost.

Consumer Unit (Fuse Box) Upgrades

You might need a consumer unit upgrade if:

  • ⚠You have an old rewirable fuse box (pre-1990s)
  • ⚠No RCD protection on circuits
  • ⚠All spare ways (slots) are already used

Upgrade Cost:

New consumer unit: £400-£800. Your installer will assess this during the Heat Loss Survey.

Next Steps

  1. 1.
    Check your supply

    Look at your main fuse - one cable = single-phase (you're fine)

  2. 2.
    Get a Heat Loss Survey

    Tells you exact heat pump size needed (required for BUS grant)

  3. 3.
    Installer assesses electrical

    They'll confirm if any upgrades needed - usually none

Cost CalculatorFull Cost Breakdown

Common Questions

Will a heat pump overload my electrics?

No. Modern UK homes have 100A supply, heat pumps draw 2-6A. Even with other appliances running, you have plenty of capacity.

Do I need to tell my DNO (electricity supplier)?

No notification required for residential heat pumps under 16 kW on single-phase. Your installer handles all required notifications.

Can I run a heat pump and EV charger together?

Yes. Load-balancing technology prevents overload. Heat pump (3-6 kW) + EV charger (7 kW) is well within a 100A supply.

What if my main fuse is only 60A?

Contact your DNO for free upgrade to 100A. Takes 2-6 weeks, usually free. Do this before heat pump installation.

Summary

✓95% of UK homes have single-phase power - perfectly adequate for heat pumps

✓Heat pumps up to 16 kW work on single-phase (covers 99% of homes)

✓Electrical work costs £200-£500 (included in installation)

✓Three-phase only needed for very large/commercial properties

Calculate your heat pump cost (including electrical work): Free Calculator

Last updated: August 2026

Related guides: Installation Cost Breakdown • BUS Grant Eligibility • Keeping Existing Radiators