Use Cold Water in Your Cleaning Machines

Whether it's laundry or dishes, turn down the dial for environmental savings and gleaming results.

It is a discussion we've been having on this website since its inception more than a decade ago: Does cold water clean as well as hot? Back in 2008, Collin Dunn wrote that pushing the 'hot' button on your washing machine was equivalent to driving 9 miles in a car. In 2011, John Laumer argued that refusal to use cold water is "bad for our budgets as well as the environment" and that, unless you're a car mechanic, you don't need hot water for everyday washing.

Today I am here with yet another defence of the cold-water team, inspired by an article in Apartment Therapy. Kay Gebhardt, a chemist and senior scientist for sustainability at Seventh Generation (a cleaning company), was interviewed for her opinion on the matter. She believes consumer practices are outdated:

"The perception that hot water cleans better than cold stems from the way we did laundry years and years ago. Back then, heat was useful because it sped up the cleaning process when detergents and machines were less efficient."

Nowadays, detergents have been formulated to be effective even in cold water. They no longer need to be "activated" with hot water, as earlier versions did, and contain enzymes that, in Gebhardt's words, "literally cut up the soils and allow the surfactants to move the stains off the clothing."

Cold water has additional benefits. It doesn't fix stains in place the way hot water does, meaning you can actually get cleaner-looking clothes as a result; and it is gentler on fabrics, increasing their longevity, especially if you hang-dry instead of putting them in the dryer. Combined with a bit of oxygen bleach and an extended pre-soak, cold water can work wonders on tough dirt.

The same applies to automatic dishwashers, where agitation and modern detergents are more than sufficient to clean dishes, no hot water or heated drying cycle needed. The hot water in a dishwasher usually tops out at 120 degrees F, which isn't enough to sanitize dishes; you need 150F for that. When it comes to clothes, the dryer can sanitize, but not the washer, and sunlight is just as effective – another reason to hang-dry outside. And you really only need to sanitize when "the soiled clothes are harboring nasty bacteria, such as fecal matter on cloth diapers, or vomit resulting from an illness."

The only time when hot water makes sense is when you're washing clothes or dishes by hand. For the former, it's mainly a matter of comfort, as the laundry detergent works the same regardless of the way you're washing clothes. (Some natural powdered detergents do require warm water to dissolve, but you can do that in a small dish before adding to the washer or sink.) For the latter, liquid dish detergents are formulated to need warm or hot water to kickstart their degreasing power. Finally, if you live in a cold climate and your water supply is frigidly cold in winter – say, almost at freezing level – then it makes sense to turn up the heat a bit.

Otherwise, turning down the heat on the washing machine and dishwasher can save you a boatload of energy. When it comes to laundry, three-quarters of emissions associated with a single load comes from heating the water itself, so a small tweak practiced over time can go a long way toward reducing your household's impact.