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.
Part P registered
Tested to BS 7671
60 minute target response
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 01273 095564 and we will work out what the supply and the board can take.