“Three-phase or single-phase?” comes up on almost every commercial oven or chargrill enquiry. For people buying their first piece of serious kitchen kit, it’s also the question that causes the most confusion, because the answer depends on what’s already coming into the building, not on what the equipment needs.

Here’s what’s actually going on.

What single-phase and three-phase actually are

Single-phase is what almost every UK home has. One live wire, one neutral, one earth. The supply runs at 230V, and domestic circuits are usually 13A (for plug sockets) or 32A (for a cooker). A 13A socket tops out at about 3 kW of continuous draw — enough for a kettle, a domestic oven or a small countertop fryer. A 32A cooker circuit gets you closer to 7 kW.

Three-phase is what commercial kitchens and most non-domestic buildings run on. Instead of one live wire you’ve got three, each 120 degrees out of phase with the others. The practical upshot: you can pull far more power per connection, and motors (in mixers, dishwashers, extractor fans) run smoother and last longer. A typical three-phase commercial oven wants 32A or 63A per phase — roughly 22 kW and 43 kW respectively. You’d never get that through a single-phase cooker circuit.

Why commercial kit almost always wants three-phase

Take a 10-grid combi oven as an example. It wants about 20 kW to heat up hard. Feed that through a single-phase 32A cooker circuit and you’d trip the breaker — a 32A single-phase circuit caps out at around 7 kW sustained. Feed it through a three-phase 32A supply and you’re comfortable, because 32A flows on each of three legs.

The same logic applies to:

  • Chargrills (gas ones excepted) — most need 16–32A three-phase
  • Planetary mixers above about 20 litres. Three-phase motors run quieter and draw less current per phase
  • Six-plate induction hobs — single-phase versions exist but are rare and expensive
  • Blast chillers — large refrigeration compressors are almost always three-phase
  • Rotisserie ovens — big three-phase heating elements
  • Dishwashers above the undercounter size

Some of the above have gas equivalents. Chargrills famously so. Combi ovens, as we’ve covered. Gas mixers don’t really exist. If your building is strictly single-phase and can’t be upgraded, look hard at the gas versions of anything that has one.

Checking what you have

Walk up to your consumer unit (the fuse box) and count the incoming cables. A single-phase supply has three thick wires coming in: one live, one neutral, one earth. A three-phase supply has five: three lives, one neutral, one earth.

The main switch is another tell. Single-phase main switches are usually 100A and physically smaller. Three-phase main switches will have three poles (three separate switches ganged together) and the panel will often carry “3-phase” or “415V” markings.

If in doubt, get a sparky to check before placing an order. A 45-minute site visit is much cheaper than a fryer sitting on a pallet because nothing in the building can run it.

Upgrading from single to three-phase

If you’re in a commercial unit and genuinely single-phase, your DNO — the regional Distribution Network Operator, e.g. UK Power Networks in the south-east — can usually install a three-phase supply. Costs vary enormously by region and site: anywhere from £1,500 for a simple pavement dig to £15,000 or more if the street needs a new transformer. Lead times can be weeks or months.

Before you commit, get a quote. The sticker price on the equipment is often the small bit of the total spend once a supply upgrade is in the picture.

The short version

  • If the building already has a three-phase supply, buy whatever kit fits the menu
  • If it’s single-phase, lean gas where you can, and check specs carefully on anything electric
  • If you’re mid-refit, get a sparky to cost a three-phase supply while the rest of the budget is still fluid. Retrofitting later always costs more

Still unclear what you’ve got? Take a photo of the consumer unit and send it via our contact form. We’ll give you a straight read on whether the kit you’re eyeing will actually run.