Is 3 phase electricity more expensive than single phase?

Question

We're looking at getting an EV charger and possibly a heat pump, and someone mentioned upgrading to 3 phase. Does it cost more to run day to day, and what's the upgrade itself likely to cost?

Izuchukwu Emmanuel · Answer

A 3-phase electricity does not inherently cost more to use. Your day-to-day electricity bill is usually based on the number of kWh you consume, not whether your supply is single-phase or three-phase.

Running costs

If you upgrade to 3-phase:
- Energy price: Usually the same tariff (or very similar) as single-phase for residential customers.
- Standing charge: In many areas it's the same, though some suppliers or network operators may have a slightly higher standing charge for 3-phase residential supplies.
- Efficiency: There's no meaningful increase in electricity consumption just because you have 3-phase. In some cases, large motors run more efficiently on 3-phase, but for a home with an EV charger and heat pump, the difference is negligible.

So if your EV and heat pump use 10,000 kWh per year, they'll cost about the same to run whether you're on single- or three-phase.

Why people upgrade

A typical UK single-phase supply is often limited to around 60–100 A (roughly 14–23 kW available at any one time).
Adding:
- a 7 kW EV charger,
- a 10–16 kW heat pump,
- an electric shower,
- an induction hob,
- an oven, 
and other household loads can mean you're close to the limit during peak times.

A 3-phase supply gives you much more capacity, making it easier to run multiple high-power appliances without exceeding the supply limit.

Cost of upgrading

This is where costs vary enormously.

Typical ranges are:
- Simple upgrade where 3-phase is already nearby: around £1,000–£3,000
- Typical domestic conversion: around £3,000–£8,000
- If the network needs significant reinforcement or a long new cable: £10,000+ isn't unheard of.

The biggest factor is what your local distribution network operator (DNO) has to do:

- replace the service cable?
- upgrade the cut-out and meter?
- reinforce the local network?

Other costs

You'll also likely need:
- a new 3-phase electricity meter (usually arranged by your supplier),
- possibly a new 3-phase consumer unit or modifications to your existing one,
- an electrician to reconnect circuits.

These can add anywhere from a few hundred pounds to a couple of thousand pounds depending on the installation.

Steven · Answer

Its a question you need to ask your DNO on the price to upgrade, as circumstaces vary depending on the scale of the work involved. Do you know the wattage of the car charger and heat pump system you are planning on installing?

Chris · Answer

The actual running cost of Three Phase will be similar to Single Phase, but there will be a cost to upgrading to Three phase, the cost will be determined by the installer

Lewis · Answer

Ev chargers charge on 3 phase even if the supply is single phase it’s a lot more efficient and won’t cost more day to day. If your property is currently single phase it will cost a lot to have it converted, I couldn’t tell you how much exactly the dno will charge you but certainly in the thousands. The main difference is speed of charging.

Is 3 phase electricity more expensive than single phase?

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