Why should you wash at 30 degrees instead of 40 degrees?

For your colored clothes, 30 °C is the right temperature. Here's why, and when you should set the temperature higher.

1) At 30 °C, your clothes are clean

Modern laundry detergents contain enzymes that work effectively at low temperatures. So you don't need hot water to remove everyday dirt and sweat.

It is also sufficient from a hygiene standpoint. This study shows that “more than 99.99% of enveloped viruses are inactivated by washing textiles at 20 °C.” Non-enveloped viruses, which are more resistant, are eliminated at temperatures as low as 30 °C when washed with a disinfectant detergent.

2) At 40 °C, your colors will fade

The hotter the water, the more it breaks down dyes. This study shows that color loss is significantly greater in a 40 °C wash cycle than in a cold, quick cycle. And if you want to see this for yourself, check out this Instagram video that compares color fading in fabric washed at different temperatures.

3) At 40 °C, it's more expensive and less eco-friendly

Heating water accounts for the bulk of a washing machine’s energy consumption. A wash cycle at 40°C uses 30% more electricity than one at 30°C (according to this study).

The two exceptions: white items and household linens

Wash whites at 40 °C using powdered detergent. The powder contains a bleaching agent—sodium percarbonate—which is effective only at temperatures of 40 °C or higher. At lower temperatures, your whites will turn gray over time. Do not use it on colored items: this same agent will eventually cause them to fade.

Household linens deserve a 60°C wash every now and then. Sheets, towels, and dishcloths accumulate dust mites and bacteria. Washing them at 60°C eliminates these, removes stubborn musty odors, and rids the linens of germs after an illness. Bonus: This hot cycle also cleans your washing machine of any lingering odors.