What's the carbon footprint of … a load of laundry?

The carbon footprint of a load of laundry:
0.6 kg CO2e washed at 30°C, dried on the line
0.7 kg CO2e washed at 40°C, dried on the line
2.4 kg CO2e washed at 40°C, tumble-dried in a vented dryer
3.3 kg CO2e washed at 60°C, dried in a combined washer-dryer

Depending on how you do it, and how many loads you get through each week, laundry can contribute a surprising amount to your carbon footprint. Washing and drying a load every two days creates around 440kg of CO2e each year, which is equivalent to flying from London to Glasgow and back with 15-mile taxi rides to and from the airports.

Modern washing powders work just as well at 30°C, so there is a very simple saving to be had here of 100g per wash just by turning the temperature down. But the much bigger savings relate to drying. As the numbers above show, for a typical 40°C wash nearly three-quarters of the carbon footprint comes from the drying rather than the washing – which reflects the general rule of thumb that the more heat an appliance generates, the more energy it takes to run.

Part of the problem is that tumble dryers (like dishwashers and washing machines) generally use electricity to generate their heat. This is typically more than twice as carbon-intensive as creating heat from gas – for the simple reason that, in the case of electricity, most of the energy in the fuel gets wasted up the cooling tower of a power plant, with yet more getting lost in transmission to the home. Gas tumble-dryers do exist but aren't yet popular, despite consuming far less energy.

However your dryer is powered, if you use a conventional vented model, most of the heat is simply pumped out to the outside world, which is sensible in the summer but wasteful in the colder months when you will simultaneously be heating the home by other means. Unvented condensing dryers use a little bit more energy per cycle, but in the winter all that heat stays inside your house, where theoretically it should reduce the burden on the heating system. So the relative impact of each depends on whether you use the dryer all year around or just in the winter when the clothes-lines doesn't work as well. (Where the machine is positioned is also relevant, as the captured heat will be more of a benefit in, say, the kitchen, than it will in a garage.)

Ultimately, though, all tumble drying is wasteful. A household running a dryer 200 times a year could save nearly half a tonne of CO2e by switching to a clothes rack or washing line. When drying clothes inside on a rack, the evaporation from the wet fabrics will cool the home to cool down a fraction but this is a marginal effect – and although it's a disadvantage in the winter, it's a bonus on a hot summer's day, when you'll get some free air conditioning.

Whichever way you dry you clothes, it makes sense to use a washer with a good spin function. It is much quicker and more efficient to remove most of the water by spinning it off than by evaporating it in a dryer.

All the figures listed above are based on a full 5kg load (half loads use a little less energy each time but they work out as much less efficient per garment washed). They include around 220g per wash for the embodied emissions in the appliances themselves. If this estimate is correct, the manufacture and delivery of the appliances accounts for nearly 10% of the total carbon footprint of each wash.

You can probably improve on the lifetime of your washer and/or dryer if you look after it and get it repaired when it breaks. Switching from a typical 1998 machine to a new one with an 'A' rating might gain you around 10% in efficiency – just enough to offset the emissions created in the new machine's manufacture and delivery. In other words, unless your machine is particularly cranky and inefficient there is no real carbon case for getting a new one unless you have to.

The final piece of the puzzle is the frequency with which you wash stuff. No one wants to go around smelly, but it's worth at least asking the question: does stuff go in the wash unnecessarily often? If you can reduce the number of loads you do without yourself or anyone else noticing any difference, there is a time saving to be had, too.

See more carbon footprints.