Before you begin
What you need to work out appliance costs
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
Understanding what your appliances cost to run
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 the night or EV rate you enter, 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.
Worked example
The same question, answered end to end
A household on a 36c unit rate with an 85c daily standing charge, heating a 117-litre cylinder to 65 °C four times a week and running the eleven appliances the form starts with.
What was entered
- Electricity at 36c per kWh, including VAT, with an 85c daily standing charge.
- A 117-litre cylinder, thermostat at 65 °C, heated from cold four times a week.
- The starting appliance list: kettle, fridge-freezer, oven, dishwasher, washing machine, tumble dryer, electric shower, television, laptop, router and LED lighting.
How it is worked out
Each appliance's typical energy per use is multiplied by how often you said you use it, then priced at 36c per kWh.
Heating 117 litres from 12 °C to 65 °C takes about 7.2 kWh, so one full heat costs about €2.60; four heats a week makes the immersion the largest single line.
The weekly total is multiplied by 52 for the annual usage cost.
The standing charge is added separately — 85c × 365 — to reach the estimated annual bill, because it is payable whatever you switch off.
The loads that can genuinely be moved overnight are re-priced at the night rate you entered, and the difference is the night-rate saving.
What the tool returns
- Weekly usage cost
- €28
- Annual usage cost
- €1,431
- Estimated annual bill
- €1,742
- Night-rate saving available
- €351
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.