Before you begin
What this tool needs
Copy the per-kWh unit rate and the daily standing charge from your latest bill rather than using the defaults.
Tick only what you use. Amounts are weekly unless the unit beside the box says otherwise.
The immersion is costed from cold water at 12°C and a 3 kW element.
Reading the answer
What your result means
Work down the ranked list from the top. The first two or three items usually account for most of the spend you can actually control.
Changing the unit rate lets you compare a standard tariff with a genuine night or EV rate.
The standing charge is unavoidable, so treat the usage total as the part you can influence.
Boundaries
Assumptions and limitations
Working assumptions
- Typical appliance energy per use is used, not a reading from your exact model.
- An appliance you add yourself is costed simply as watts × hours, with no thermostat or duty cycle applied.
- The night-rate comparison uses 21c/kWh as a comparison figure, and applies it only to loads that can genuinely be moved.
Where to be careful
- Thermostats, appliance age, programme choice and household behaviour can materially change the result.
- Use an energy-monitoring plug for a precise reading where the appliance can safely be measured.
- Cooking, heating and pump figures assume the appliance cycles on and off as its thermostat allows, rather than drawing full power the whole time it is on.
Common questions
Questions about this tool
Does leaving the immersion on use 3 kW continuously?
Not with a working thermostat. It heats at full power, then cycles to replace heat lost from the cylinder. Heating unused water and poor insulation are the larger wastes.
My appliance is not listed. What do I do?
Add it at the bottom of the list with its wattage and the hours you use it each week. The rating plate, the manual or a plug-in energy monitor will give you the wattage.
Why is the standing charge shown separately?
It is payable whether or not any particular appliance runs, so keeping it apart makes individual uses comparable. The estimated bill line adds it back.