22kW vs 7kW Home EV Charger: Do You Need Three-Phase?

A 22kW home charger looks like the obvious future-proof choice — three times the speed of a 7kW unit, ready for whatever battery capacity the next EV brings. The reality is more nuanced. The vast majority of UK domestic supplies are single-phase, which physically caps a home charger at 7.4kW regardless of what the unit says on the box. Going to 22kW means a three-phase supply upgrade that most households can't justify on the maths. This guide explains exactly when 22kW is worth it, what the DNO upgrade involves, and which households should stick with 7kW.

The headline number on a charger box is the maximum the unit can deliver — not what your house can supply. UK domestic electricity is delivered as either:

• Single-phase — one live conductor at 230V, capped at the main fuse rating (usually 60A, 80A, or 100A). The maximum continuous draw on a 7.4kW charger is 32A at 230V = 7,360W. This is the supply about 95% of UK domestic properties have.
• Three-phase — three live conductors at 400V phase-to-phase. A three-phase home charger draws 32A on each phase = 22,000W. This is what new-build executive homes, larger detached houses with electric heating, and farms typically have.

The crucial point: a 22kW charger plugged into a single-phase supply will not deliver 22kW. It either won't function (most three-phase units refuse to run on single-phase), or it will fall back to roughly 7.4kW (some hybrid units), or it will trip your main fuse at startup. You cannot upgrade the speed by buying a faster charger — the supply has to come first.

If you have single-phase today and want to [install](/blog/how-to-install-home-ev-charger-uk/) a 22kW charger, the supply upgrade typically follows this rough cost structure:

• £3,000–£5,000: standard upgrade where the existing service cable can be reused. The DNO swaps the meter, fits a three-phase fuse and meter assembly, and installs three-phase tails to your consumer unit. You then pay a separate consumer-unit upgrade (£500–£1,500) to handle the additional circuits.
• £5,000–£10,000: where the service cable from the street has to be upgraded. This is common in older properties on rural overhead lines or in conservation areas where the LV main isn't already three-phase to the property boundary.
• £10,000+: where new ducting has to be excavated, where the local LV transformer has insufficient capacity, or where the property is on an isolated rural single-phase spur.

These figures don't include the charger itself (£900–£1,400 for a 22kW unit) or your electrician's labour for the consumer-unit work. Realistically, budget £4,000–£7,000 all-in for a typical UK semi-detached upgrade. DNO timelines run 4–12 weeks from initial enquiry to energising, so the upgrade is also a meaningful project commitment.

The case for 22kW comes down to one question: do you need to add more than 60kWh of charge in a single session faster than overnight? Almost no UK household answers yes. The cases that do:

• Two EVs that both charge overnight on the same wallbox. A single 7kW unit can deliver around 42kWh in a six-hour off-peak window — enough for one car's daily commute but not two large packs both arriving at low SoC. A 22kW unit delivers ~130kWh in the same window: more than two depleted packs need.
• High-mileage drivers with large batteries. A taxi or sales-rep driver returning home with 10% SoC on a 100kWh battery needs 90kWh of charge to be ready by morning — a 7kW unit takes 13 hours, which doesn't fit inside any UK off-peak window. A 22kW unit takes ~4.5 hours, well inside the cheap window.
• Daytime charging from solar. Households with 6kW+ of solar PV and a 22kW charger can dump excess generation into the EV in summer at meaningful rates without exporting to the grid. A 7kW unit caps the diversion at 7kW, leaving the remainder going out at the SEG rate.
• Small fleets sharing one driveway. Three or four cars rotating through the same wallbox — a small business or extended household — adds up to enough kWh that 22kW pays back, especially if some sessions are mid-day rather than overnight.

If you don't fit one of those four cases, 7kW is fine. The maths on a typical UK driver's 8,000–15,000 miles a year is overwhelming: even at 4 mi/kWh (a relatively inefficient EV), that's ~3,000kWh per year, or ~58kWh per week. A 7kW charger delivers that in 8.5 hours total — easily absorbed across two off-peak sessions per week.

Smart tariffs like Intelligent Octopus Go, EDF GoElectric, and OVO Charge Anytime define a finite off-peak window — typically 5–7 hours overnight. The faster you can charge, the more kWh you can pull at the cheap rate. A 22kW charger lets you put a full 100kWh battery onto cheap electrons inside that window where a 7kW charger would force half of the session into peak hours.

For most households this doesn't matter — typical overnight charging fits comfortably inside the cheap window at 7kW. The exception is large-battery EVs (100kWh+ Mercedes EQS, BMW iX, Lucid Air imports) or households deliberately running their packs down to a low daily SoC. In those cases the 22kW upgrade does change the maths on tariff economics, not just charging time.

Many EVs cap their onboard AC charger below 22kW regardless of what the wall unit can supply. The car's onboard charger rating is the actual ceiling. Examples from current UK lineups:

• 11kW max (3-phase): BMW i4, BMW iX, Tesla Model 3 / Y (post-2021), Mercedes EQE / EQS, Audi e-tron / Q4 e-tron, Volkswagen ID.4 / ID.5, Polestar 2.
• 22kW max (3-phase): Renault Megane E-Tech / Scenic E-Tech (optional), Smart #1, Audi e-tron GT, Porsche Taycan (optional), Tesla Model S / X (older).
• 7.4kW max (single-phase): Hyundai Kona Electric (older), Nissan Leaf, MG4, MG5, BYD Atto 3, Toyota bZ4X, Subaru Solterra.

So even if you upgrade to three-phase and a 22kW wallbox, an 11kW car will only ever pull 11kW. That's still 50% faster than 7kW (about 65kWh in six hours), but it's not the headline figure. Check your specific model's onboard charger spec on the manufacturer's site before committing to a 22kW supply upgrade — it's the most common reason 22kW upgrades disappoint in real use.

For 95% of UK households, a 7kW single-phase charger is the right call — fully charges any current EV overnight, fits cleanly inside every smart-tariff window, and avoids a five-figure supply upgrade. Spend the saved budget on a quality charger with strong tariff support: see our best home EV charger comparison.

For the small minority — high-mileage drivers, two-EV households charging overnight, large-battery imports, or solar-heavy installs — 22kW genuinely earns its keep. [Talk to your DNO](/blog/dno-notification-g98-g99-ev-charger/) before the wallbox supplier; the supply upgrade is the longer pole and the larger spend, and a charger purchase is meaningless until that's quoted.