How much water does a washing machine use per cycle?

Water use is the part of laundry cost that people either ignore entirely or wildly overestimate. Machines from the 1990s used well over a hundred litres a cycle; efficiency requirements have pushed that down a long way since. The number that matters is not a general one, though — it is the one in your own manual, against the programme you actually select.

What you'll need

• The machine's manual, or the model number to find it online
• Your water bill, for the rate per cubic metre (optional)

Step by step

1. Find the programme table in the manual.Nearly every manual has a table listing each programme with its water consumption in litres, its energy in kWh and its duration. That is the authoritative figure for your machine, and it varies far more between programmes than most people expect.
2. Understand that the machine adjusts to the load.Modern machines weigh the drum contents and fill proportionally. A half load genuinely uses less water, which is why the old advice to always wait for a full load has softened.
3. Note which options add water.An extra rinse adds a full rinse's worth. A prewash adds a short fill and drain. Synthetics and delicates programmes deliberately use more water than cottons, to keep fabric moving freely and reduce creasing.
4. Convert to cost if you are metered.Litres divided by 1,000 gives cubic metres. Multiply by the combined water plus sewerage rate on your bill — sewerage is charged on the same volume, so use both figures, not just the supply one.
5. Ignore it entirely if you are not metered.On a rateable-value bill the water is not costed by volume at all, so water use has no effect on what you pay. The electricity still does.
6. Put it in proportion against the rest of the house.A full cotton wash is roughly the same as one bath, or a shower of a few minutes. It is a real quantity but rarely the largest one in a household, and a running toilet outweighs it many times over.
7. Check for the specific fault that wastes water.A machine that fills and drains repeatedly, never reaching level, is self-siphoning through the waste hose — usually because the hose is pushed too far into the standpipe or the high loop has been lost. It quietly triples water use and washes badly.

Tips

• If your water bill has jumped and the machine is the suspect, watch a full cycle. A machine draining while it fills is unmistakable once you are listening for it.
• Water-condensing washer dryers use additional mains water throughout the drying phase, which does not appear in the wash-cycle figure at all. Check the drying figure separately.
• An extra rinse is worth its water for sensitive skin. Adding one routinely to every wash out of habit is not.

Common mistakes

• Assuming water is the main cost of a wash — On most tariffs the electricity to heat the water costs more than the water itself, and on an unmetered bill the water costs nothing marginal at all.
• Using the wrong rate to convert litres to money — Metered households are charged for supply and for sewerage on the same volume. Using only the supply rate roughly halves the apparent cost.

Questions people ask