Single phase vs three phase

When you compare home EV chargers, the terms single phase and three phase appear quickly. The short version is simple: most UK homes can use a 7kW charger, while faster 11kW or 22kW AC charging usually needs a three phase supply and a car that can accept it.

Quick answer

If you have a normal UK domestic supply, plan around a 7kW single phase charger unless an installer or electrician tells you otherwise. That is usually enough for overnight charging on Octopus Go or Intelligent Octopus Go.

Three phase can be useful for large homes, farms, workshops, multiple EVs or short daytime turnaround charging. For a typical driveway charger, it is rarely worth paying for a supply upgrade just to chase a bigger number on the charger’s spec sheet.

What is the difference?

A single phase supply brings one live electrical phase into the property. It is the normal setup for most homes and supports the familiar 7kW home charger, subject to the existing fuse, wiring and DNO checks.

A three phase supply brings three live phases into the property. That lets the load be spread across phases, which is why three phase is common in commercial buildings and larger sites with heavier electrical demand.

You do not need to understand the engineering detail to make the charger decision. The practical question is whether your home, charger and car can all support more than 7kW AC charging.

How to tell what you have

A charger installer or qualified electrician is the safest person to confirm your supply during a survey. You can still do a few rough checks before booking anything:

• Meter and service head: Three phase equipment is usually larger and may have three main fuses or clearly marked phase labels.
• Main switch: A three phase consumer unit often has a wider three-pole main switch rather than a single domestic main switch.
• Property type: Ordinary houses are usually single phase. Larger detached homes, farms, converted buildings, workshops and some newer or higher-demand properties are more likely to have three phase.
• DNO confirmation: Your Distribution Network Operator can confirm the connection type. The Energy Networks Association has a tool to find your network operator.

Do not rely only on counting cables. Older or altered installations can be misleading and opening supply equipment is not a DIY check.

What it means for charging speed

Single phase, usually up to about 7kW at home: This is the common domestic setup. A 7kW charger can add roughly 25 to 30 miles of range per hour, depending on the car, temperature and charging losses.

Three phase, often 11kW or 22kW where supported: A three phase charger can be much faster, but only if the property supply, charger and car all support it. Many EVs on UK driveways still have a single phase onboard AC charger, so a 22kW wallbox will not automatically charge every car at 22kW.

For context, a 7kW charger running through a six-hour cheap window can add around 40kWh before losses. That is enough for a lot of normal weekly driving patterns, especially if the car is plugged in regularly rather than left until nearly empty.

DNO checks matter more than the label

EV chargers add a large, regular electrical load. That is why the installer must consider your fuse rating, existing appliances, earthing, cable route and whether the local network needs to be notified or asked for approval.

Octopus says it informs the DNO for charger installs and may need extra checks for looped supplies, fuse upgrades, second chargers or a possible three phase supply. ENA guidance says installers should use the low-carbon technology process, now through Connect Direct, to decide whether the DNO can approve the installation quickly or needs to assess the connection before work starts.

GOV.UK guidance says a charger installer should assess smaller installations and decide whether the DNO is informed before or after installation. Where a new or upgraded connection is needed, the DNO quote and delivery timescale depend on connection size and site work; the April 2023 reinforcement-cost change does not make every service-head, meter, cable, electrician or charger change free.

This is not just paperwork. It is what stops a home charger from overloading old supply equipment or causing network problems on a street where several homes add heat pumps and EVs at once.

Do you need three phase for Octopus Go or Intelligent Octopus Go?

Usually, no. Octopus Go and Intelligent Octopus Go are about when and how charging is scheduled, not whether the home has three phase.

For Intelligent Octopus Go, the important checks are:

• whether you have a compatible EV or compatible charger
• whether your smart meter setup is suitable and sending half-hourly readings
• whether the car can be plugged in for long enough to meet the schedule
• whether charger, car and app timers are not fighting each other
• whether Octopus billing evidence comes from smart-meter data, not only from a charger or vehicle app screenshot

A three phase charger can still be useful if you have a compatible car and genuinely need faster AC charging. It is not a shortcut around the normal Intelligent Octopus Go compatibility checks, and it will not turn an unsupported car or charger into a supported integration.

When three phase may be worth exploring

Consider asking about three phase if one of these is true:

• You need to charge two or more EVs at home and the existing supply is already tight.
• You run a high-demand home business, workshop or farm from the property.
• You have a large heat pump, battery system or other heavy electrical loads alongside the EV charger.
• You often need a quick turnaround between trips and cannot leave the car plugged in overnight.
• Your property already has three phase and your car can accept 11kW or 22kW AC charging.

Even then, compare the cost with simpler options first: a good 7kW smart charger, load management, a second lower-powered charger, a different charging routine or a tariff that makes overnight charging cheaper.

Cost and disruption

A three phase upgrade is not like swapping a socket. The DNO may need to survey the property, check local capacity, quote for connection work and schedule any cable or service-head changes. GOV.UK guidance for larger or upgraded EV connections says quotes and timescales vary by connection size and site requirements.

Some network reinforcement costs are no longer charged to demand connection customers in the way they used to be, but that does not mean every upgrade is free. Site work, connection work, meter changes, electrician time and charger changes can still make the project expensive or slow.

Ask for a proper quote before assuming three phase is a sensible EV cost. For many households, the same money is better spent on a reliable compatible charger and making sure the car can use cheap overnight electricity consistently.

Quick comparison

Sources checked on 24 May 2026

• Octopus EV charger installation FAQs for DNO notification, looped supplies, second chargers, fuse upgrades, installation timing and Intelligent Octopus Go charger-fit checks.
• Energy Networks Association EV and heat-pump connection guidance for Connect Direct, DNO assessment and low-carbon-technology application rules.
• GOV.UK chargepoint electricity-network guidance for upgraded-connection timing, quotations and the reinforcement-cost caveat.

Bottom line

For most Octopus households, single phase and a 7kW charger is the sensible baseline. It is simple, widely supported and lines up well with overnight smart tariffs.

Three phase is worth understanding, not chasing by default. If your installer flags it, treat it as an electrical capacity question first and an EV charging speed question second.

If you are choosing hardware, start with our compatible chargers guide. If you are still working out whether home charging is practical at all, the home charging basics guide is the better next step.