Installing 3-Phase Power at Home

If you are considering the installation of a fast 22kW EV home charger you may need to upgrade your current power supply from single phase to 3-phase.

This guide will help you understand your current setup and the steps for upgrading your supply to 3-phase power.

uk consumer unit switchboard

Understanding 3-Phase Power

You can get 3-phase supply installed in your home by your local Distribution Network Operator (DNO). The Network Operator is the company that manages the energy supply for your area, you (or your electrician) must apply to the DNO to have the work approved. The DNO is the only entity allowed to upgrade the supply.

Single-phase electricity is standard in UK homes and is used to power the appliances we use daily. Higher power equipment (such as a 22kW EV charger) will require a 3-phase supply. 3-phase uses less conductor material to transmit the current, this makes it more economical than a standard single-phase supply.

Finding your DNO

If you are all set to upgrade your electricity supply you need to understand who the local Distribution Network Operator is in your area. You can find out by entering your postcode via the Energy Networks Association website. The results will tell you who your electricity DNO is, it also provides details for your Gas DNO along with contact details for each provider.

How does 3-phase electricity work?

The ‘phase’ of an electricity supply refers to how the load is dispersed. 3-phase power consists of 3 wires running on the same frequency, each wire is separated by 120 degrees.

Imagine three sets of waves (representing the currents) starting at different times, but repeating the same pattern. When one wave is at its peak, the other two are less so, and this pattern repeats. This means that power is always being supplied at a consistent rate, but because the currents are out of phase with each other, they can be used to more effectively power large motors and heavy loads.

The constant rate of the 3 phases ensures that power transfer is constant and can handle a heavier load at a supply of around 3 times that of a single phase.

Identifying if you have 3-phase power

If you are planning to install a 22kW charger you must first discover if your property already has a 3-phase supply in place. Here’s a list of steps to determine the phase of your current supply:

  • Check the consumer unit ( the fuse board). If your consumer unit houses 3 service fuses, you have a 3-phase power supply. If there is only 1 service fuse then your supply is single phase
  • Check your Electricity Bill. Many electricity suppliers will list the phase of a supply within the bill

  • Check the electricity meter. Some (but not all) electricity meters will indicate your property’s type of power supply. The meter may not describe the supply as 3-phase, it could be referred to as poly-phase or tri-phase

Availability for residential properties

Residential properties are able to upgrade their electricity supply from single-phase to 3 phase supply. You should initially contact your local Distribution Network Operator to determine if the upgrade is possible before planning the installation of a home EV charger

Costs and Installation

The minimum cost charged by the UK Power Networks (the DPO responsible for East Anglia & London) for upgrading an electricity supply to Phase 3 is £1,800 inclusive of VAT. However, the final cost of an installation will depend entirely on the complexity and technical challenges facing the local DNO carrying out the work.

UK Power Networks publishes a summary of average cost and completion time publically. UK Power Networks 2022 average cost to upgrade to phase 3 supply is:

  • 12% of Phase 3 upgrades cost £1,700 – £3,500 (+VAT)
  • 70% of Phase 3 upgrades cost £3,500 – £6,000 (+VAT)
  • 18% of Phase 3 upgrades cost over £6,000 (+VAT)

The majority of people can expect to pay over £3,500 (+VAT) to upgrade to phase 3. Why do costs vary so much? Let’s look at the factors that can impact costs.

Factors impacting installation costs

Digging the external cable from your house will likely need upgrading which means the DNO must expose the cable in your front garden, if the cable is used to supply a neighbouring property it may be necessary to dig in their driveway as part of the installation.

If a public footpath is dug up then the DNO will need to apply for a council permit and pay a charge. In some cases, the DNO may need to dig up the main road, there are council charges and there may be additional costs for two-way traffic lights or diversions if required.

Engineers parking will be charged if they are not able to park in your driveway. Cost is added if the engineers need to park in council bays or apply for a temporary traffic regulation order if no public bays are available. 

Installation process

The first thing you can expect is a significant amount of digging. The electricity cables supplying your property will likely be underground and therefore a large trench will need to be dug in order to access the cable (you may be able to do this yourself to reduce costs, agree with the DNO in advance). The DNO will likely need to dig outside your property too, on the footbath or main road.

The cable will be replaced and a new electricity meter box will be fitted on an external property wall, you can discuss the location of the new box with your engineer.

The engineers will connect the cables and spend some time running through a series of safety procedures to ensure your setup is correct and safe to use.

The DNO will fill in the holes but this is unlikely to be on the same day (unless you have dug this yourself, then they would not be expected to make good).

To finish up your electricity supplier needs to visit the property and install a brand new meter in the meter box. Don’t forget that your electricity supplier and your DNO are two different entities, the supplier is the company you pay your bills Forr for you to avoid having no power overnight, it is vital that you arrange for your supplier to visit on the same day as the phase 3 power upgrade.

What is the benefit of 3-phase power?

We now know that cost and effort in upgrading your electricity supply to phase 3 can be significant, so what are the benefits?

  • Increased power output is the obvious benefit of the upgrade, the voltage of 3-phase power is up to 415V compared to 230V from a single-phase supply. This allows you to run 22kW EV chargers (meaning you can charge your EV faster) and other more heavy-duty electrical devices

  • Consistent power output is achieved with a 3-phase supply, a single-phase supply can be less consistent in its delivery of electricity

  • Less prone to outages due to the consistent power output, the constant flow reduces the possibility of failure

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