How much does a washing machine cost to run per cycle?

Anyone quoting you a single figure for what a wash costs is quoting their own tariff and their own machine at you. The three inputs — kilowatt hours, pence per kilowatt hour, and litres — vary by a factor of three or more between households. The arithmetic, on the other hand, is trivial, and doing it once for your own two or three regular programmes reorders most people's assumptions about which cycle to use.

What you'll need

• Your electricity unit rate in pence per kWh, from your bill
• The machine's energy label or manual
• A plug-in energy monitor, if you want the real figure (optional)
• Your water and sewerage rate per cubic metre, if metered (optional)

Step by step

1. Find the energy used per cycle, in kilowatt hours.The energy label gives a figure for 100 cycles of the eco 40-60 programme, so divide it by 100. A label showing 60 kWh per 100 cycles means 0.6 kWh per eco cycle. The manual usually tabulates the other programmes too.
2. Do not use the machine's wattage for this.A washing machine draws around 2,000W only while the element is heating, and a small fraction of that for the rest of the cycle. Multiplying the plate rating by the cycle time overstates the cost several times over.
3. Find your unit rate.Pence per kilowatt hour, on the bill or in the supplier's app. If you are on a time-of-use tariff, use the rate for the time the machine actually runs — that alone can halve the answer.
4. Multiply the two.kWh × p/kWh = pence of electricity. 0.6 kWh at 25p per kWh is 15p. That is the whole of the electricity side.
5. Add water if you are metered.Litres per cycle divided by 1,000 gives cubic metres. Multiply by your combined water and sewerage rate per cubic metre. Fifty litres at £3 per cubic metre is 15p. On an unmetered rateable-value bill, this term is zero.
6. Add one dose of detergent.Pack price divided by the number of doses it actually gives at the dose you use. It is frequently the same order of magnitude as the electricity, and it is the one input you fully control.
7. Measure it properly if you want certainty.A plug-in energy monitor between the socket and the machine records actual kWh over a full cycle, including your incoming water temperature and your load size. It is the only way to get a true figure for the programme you really use, and some libraries lend them.
8. Now compare your own programmes.Run the same calculation for a 30 degree cycle, a 40 and a 60 on your machine. The gap between them is much larger than the gap between machines, and it is entirely under your control.
9. Remember the cost that happens afterwards.For anyone who tumble dries, the drying cost usually exceeds the washing cost. A higher spin speed adds almost nothing to the wash and removes water the dryer would otherwise have to boil off. It is the largest saving in the room.

Tips

• Temperature dominates. Dropping a regular 60 degree load to 40 saves far more than any change of detergent, programme length or machine.
• Cycle length has surprisingly little effect on cost. A three-hour eco cycle can easily cost less than a one-hour 60 degree one, because the motor is cheap to run and the element is not.
• If you are on Economy 7 or a similar tariff, a delay timer that runs the machine in the cheap window is a genuine and immediate saving with no behaviour change at all.
• Standby draw on a modern machine is negligible. Switching it off at the wall is good practice for leak and fire safety, not for the bill.

Common mistakes

• Multiplying the machine's wattage by the cycle time — The heating element only runs for part of the cycle. This method typically overstates the cost by three or four times and leads people to avoid the wrong things.
• Treating the energy label figure as your cycle's cost — It describes 100 eco cycles at mixed loads. If you mostly run a 60 degree cottons wash, your real consumption is considerably higher than the label implies.

Questions people ask