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Ask Dr. Laundry

Ask Dr. Laundry

Cold Water Basics

By Dr. Laundry January 28, 2008

It’s January, there’s lots of snow, its winter and it’s COLD!! Larger energy bills are due to show up in your mailbox. What are some options for helping to keep these in check?

Many people are looking for ways to cut energy costs, save dollars and help the environment. Also, many companies have their eye on these trends and are developing products that can help consumers meet these needs. So I thought I would do a series of blogs on the Cold Water phenomena starting with a little background.

Basic Facts


  • Heating water is a major energy cost – Winter energy costs increase due mainly to home heating and hot water production. A key reason these costs rise in winter is the incoming cold water temperature plummet from those warm summer tap values. The cold water is delivered to your home usually from large pipes that transport surface water from a reservoir. While summertime incoming temperatures can reach the 70ºs, during winter I have seen values in the 30ºs in Northern U.S. taps. So to get to that 130ºF hot water in your tank in summer only requires a 60º (130-70) change while in winter it can require a 90º change (130-40). When you multiple this difference hot water tank after hot water tank, it really starts to add up. Unfortunately this takes a bigger chunk out of your paycheck during the winter months.

  • Some studies sponsored and published by Procter & Gamble suggest that a little more than 1/3 of the total hot water usage in the home is for laundry.

  • Further, 80-85% of the total energy consumed by a conventional top-loader washloads is from heating the hot water. The remainder is the energy needed to power the agitator for providing the mechanical energy in cleaning the clothes.

  • For a number of years, washer manufacturers have relied primarily on changing the hot to cold water ratio for the warm water wash setting to achieve the reductions necessary to achieve the lower Energy Star ratings on new machine.

  • The result has been a decrease in warm water wash temperatures. In the past it was possible to depend on a warm wash to be around 90ºF. With the newer washers and these higher cold water mixtures, it is possible for warm washes in winter to slip into the 60ºs. That is a huge difference and definitely impacts your detergent performance.


Next time I will talk about some laundering challenges presented by cool and cold water.