Upgrading to three-phase power is a significant job, and the cost varies a lot depending on your existing supply and how much work the network operator needs to do. Here’s a realistic 2026 picture.

The headline ranges

For a single-to-three-phase upgrade, the all-in cost (including DNO charges and the new board) typically falls between about £3,000 and £12,000+, and occasionally higher. The wide range is mostly down to the DNO (your distribution network operator):

• If a three-phase supply is already near your property and only a service upgrade is needed, you’re at the lower end.
• If the DNO has to dig up the road, lay new cable, or upgrade infrastructure, costs climb steeply toward the upper end.

What makes up the cost

• DNO charges — the biggest and most variable element; quoted by the network operator after you (or your electrician) apply.
• Three-phase consumer unit / distribution board — more than a domestic single-phase board.
• Internal wiring and circuits — connecting the equipment that needs three-phase.
• Electrician’s labour — design, install, test, certify.

Your electrician handles the DNO application and coordinates the works.

Domestic vs commercial

• Homes: three-phase is only worth it for genuinely heavy combined loads — a heat pump plus a 22kW EV charger plus big battery storage. For most homes it’s unnecessary (see below).
• Businesses: workshops, industrial units, and commercial premises with machinery, large HVAC, or commercial kitchens often need three-phase as standard, and the cost is part of the fit-out.

Do you actually need it? (most homes don’t)

This is the key money-saver. A standard single-phase supply comfortably runs a normal home, including a 7kW EV charger (the practical home standard) and most heat pumps. You only need three-phase for 22kW charging, large/ground-source heat pumps, or stacked heavy loads. Because a three-phase upgrade can cost thousands, it rarely makes sense purely for faster EV charging — see our 7kW vs 22kW guide. For the heat-pump angle, see our heat pump electrical guide.

How to control the cost

• Get the DNO quote early — it’s the variable that determines everything.
• Assess total demand first — you may find single-phase with a board upgrade suffices.
• Combine works — if you’re upgrading anyway, plan all heavy loads together.
• Use one electrician to design, apply to the DNO, and install — avoids gaps.

What you get

• A three-phase supply (after DNO upgrade)
• A three-phase board and dedicated circuits
• Capacity for heavy loads single-phase can’t support
• Full certification to BS 7671

Get a three-phase quote

For an honest assessment of whether you need three-phase — and a clear quote including DNO coordination across East London — GFL Electrical are your local NICEIC electricians. See our three-phase installation service or call 020 3774 5604.