Quick tool:

Load calculator

Convert watts to amps at 230V and check what is left on the circuit before you add another heater to it.

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Home Load calculator

Estimated current

13.0 A

  • Device rating32 A
  • Used41%
  • Headroom left19.0 A
  • VerdictWithin rating

This is a rule of thumb for planning, not a design calculation. Cable sizing depends on installation method, grouping, ambient temperature, length of run and disconnection times. Always have circuits designed and verified by a qualified electrician.

What it means

Reading the result

Current in amps is power in watts divided by voltage, adjusted for power factor. At 230V, a 3kW kettle draws about 13A, which is why a 13A plug fuse is the standard.

Rules of thumb worth remembering

  • A standard 13A socket outlet supplies up to 3kW at a single plug.
  • A 32A ring final circuit serves a floor of a normal house, but not two electric heaters and a tumble dryer at once.
  • Showers and cookers get their own dedicated radial circuit, sized for the appliance.
  • Anything above roughly 80 percent of the device rating for long periods deserves its own circuit.
  • Extension leads are rated for their plug, not for the sum of everything you can fit into them.

Planning a kitchen, a hot tub, a car charger or a garden office? Those loads need designing rather than estimating. Call 0333 360 8583 and we will work out what the supply and the board can take.

Lights out, burning smell or a tripping fuse board? Call us now.

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