What Temperature Should I Wash Clothes At?

Almost all the energy a washing machine uses goes into heating water. The drum turns for the same length of time whatever the setting, so in practice the temperature dial is the cost dial.

The energy difference

Approximate consumption for a standard load:

Temperature	Energy	Cost at 25p per kWh
20 degrees	0.3 kWh	about 8p
30 degrees	0.5 kWh	about 12p
40 degrees	0.8 kWh	about 20p
60 degrees	1.3 kWh	about 33p
90 degrees	2.0 kWh	about 50p

Washing at 30 rather than 40 saves roughly 40 percent. Washing at 30 rather than 60 saves nearly two thirds.

For a household doing five loads a week, moving from 40 to 30 saves something in the region of 20 to 25 a year. Modest, entirely painless, and it extends the life of clothes as a bonus.

What 30 degrees handles

Most of it. Everyday laundry is mainly body oils, sweat, light food marks and general wear, none of which needs heat to shift.

Modern detergents are formulated specifically for this. They contain enzymes that break down protein, starch and fat stains, and those enzymes are designed to be active at low temperatures. Some are actually less effective at high temperatures, because heat denatures the very enzymes doing the work.

This is the part that has genuinely changed. Advice to wash hot dates from an era of detergents that needed heat to dissolve properly and to act at all. That has not been true for a long time, and the guidance has not fully caught up.

When to go warmer

60 degrees for:

• Bedding and towels during or after illness
• Cloths, tea towels and anything used around raw meat
• Bedding where dust mites are a concern, since mites survive lower temperatures
• Heavily soiled workwear
• Reusable nappies

40 degrees for:

• Greasy or oily stains, which shift more readily with some warmth
• Heavily soiled items generally
• Synthetic sportswear that holds odour, though many do better with a dedicated detergent at 30

90 degrees almost never. It is punishing on fabric, expensive to run, and rarely achieves anything a 60 degree wash does not.

The detergent matters more than the dial

Two things affect cleaning considerably more than temperature does.

Type. Liquid detergents generally lack the oxygen bleaching agents found in powders, which are what remove tea, coffee and wine stains. Powder outperforms liquid on whites and on stubborn staining. Liquid is gentler on colours and dissolves more reliably at low temperatures.

Quantity. Both too little and too much cause problems. Too little leaves dirt behind. Too much leaves residue in the fabric and in the machine, which is a common and unsuspected cause of stiff towels and of that persistent musty smell.

Dose to the water hardness in your area and the soiling level, not to the maximum line on the cap, which is set for the worst case.

The machine smell problem

Washing consistently at low temperatures allows a biofilm of detergent residue, grease and bacteria to build up in the drum, the door seal and the detergent drawer. That biofilm is the source of the smell people notice on supposedly clean laundry.

The fix is a maintenance wash: an empty cycle at 60 or 90 degrees, roughly once a month, with either a machine cleaner or a cup of soda crystals. Wipe the door seal afterwards, since that rubber fold traps water and is where mould appears first.

Leaving the door and the detergent drawer ajar between washes lets the drum dry out and prevents most of the problem from starting.

Spin speed, which affects the bigger cost

The spin is cheap and the tumble dryer is expensive, so the spin setting matters more to the total cost of laundry than the wash temperature does.

A 1,400 rpm spin removes substantially more water than 1,000, cutting drying time and therefore the dryer’s energy use. Since drying typically costs three to five times as much as washing, choosing a faster spin is the single most effective saving in the whole process.

The exception is delicate fabrics, where a high spin causes creasing and accelerates wear.

A sensible default

Wash at 30 with a good detergent for everything normal. Use 40 for greasy or heavily soiled loads. Use 60 for bedding during illness, for cloths, and for towels every few washes. Spin as fast as the fabric allows. Run a hot maintenance wash monthly and leave the door open between loads.

That combination cleans as well as washing everything hot, costs less than half as much to run, and makes clothes last noticeably longer, since heat and agitation are what wear fabric out in the first place.

Load size and what it changes

Machines are most efficient when reasonably full, because the energy to heat water and turn a drum does not scale down proportionally with a half load.

A useful guide is a hand’s width of space at the top of the drum. Packed tight, clothes cannot move and do not clean properly, since the mechanical action of fabric rubbing against fabric does much of the work. Too empty and you are paying nearly full price for half the laundry.

Most machines now have an automatic load-sensing function that adjusts water use, which reduces but does not remove the penalty for small loads.