Laundry in cold water

What if everyone in the US washed their laundry in cold water?

I know that washing laundry in cold water saves energy, but how much?

And what if every household in the US were to switch to washing their laundry in cold water. How much energy would be saved then, and how much would we reduce our CO2 emissions?

Answer - Best Answer on Yahoo! Answers

It takes 1 Calorie (a kilocalorie) to heat one kilogram or liter of water by one degree Celsius at standard pressure and temperature.

Let's assume the average input temperature for a hot water tank is 60F (about 15C) and that the tank is set to an inefficient 140F (60C). That makes for a 45C gap in temperature.

Now let's assume that a typical top-loading washer uses 40 gallons of water per load. About half of that would be hot water for washing; assume the rest is cold water for rinsing. So we have 20 gallons of hot water, or 77.5 liters, being warmed 45C. That makes for a total of 3,875 kilocalories per load of water.

One kilowatt hour - which is a measure of power consumption typically associated with electricity use, but can apply to any form of energy use - is equivalent to 860 kilocalories, so a load of laundry uses roughly 4.5 kilowatt hours of energy.

Now let's assume that there are 100 million households in America (an average of about 3 people per household) and that each household does an average of 2 loads of laundry a week. That works out to about 10 BILLION loads of laundry a year, which if everyone were using hot water would result in about 45 BILLION kilowatt hours of energy use.

My guess is that the actual figure is much lower - probably around 20 billion kwh, because many Americans wash in cold water; in some warmer areas, the water going in is warmer than 60F; many people have sensibly lowered their hot water heater temperature from 140F to a more energy efficient 120F; and many people are switching to front-loading washers which use a lot less water and energy than top-loaders. Still, if all those people switched to cold water we could be saving the equivalent of 20 billion kwh of energy.

Since one pound of coal generates about 1 kwh of electricity that goes to your house, people whose water is heated by an electric hot water heater where the electricity comes from coal, are using at least 4.5 pounds of coal, and creating about 13 pounds of CO2 for that load of laundry (not counting the electricity to run the washer, which is much less). Since coal fired plants are very inefficient (about 35%) and gas hot water heaters are probably closer to 80% efficient, that means probably about a third as much CO2 emissions for the hot water heated by natural gas.

Still, we are talking about somewhere in the realm of 60 million TONS of CO2 emissions that could be saved if everyone stopped washing in hot water. Plus our clothes would last longer!

Green Energy Efficient Homes articles cited

View original question and answer at Yahoo! Answers

Return from Laundry in cold water to the Home energy efficiency questions page or to the Green Energy Efficient Homes site home page.

This page is part of our FAQ. See the disclaimers.

Feel free to link to this page to spread the word about energy efficiency