It is simple, the higher the temperature of the water the fastest the laundering reaction. But how does the water get hot? Energy is consumed to bring the temperature of the water to the required level. This process costs money to most of us using electricity or gas to heat the water. This should be considered when calculating the total cost of the process. The indirect environmental effect of energy consumption is also to be considered, for while it seems a small impact for an individual, consider the environmental cost when millions of user a doing their laundry with hot water, therefore consuming tons of fossil fuels.
Now several products are marketed as “Cold Water” laundry detergents. Indeed there are special detergents that are effective at low temperature, but as a general rule to achieve the same cleaning ability of hot water, cold water laundry requires higher concentration of detergent. Also addition of enzymes, cold water activators, and other ingredients are added to this products. The question raise: Are we saving energy, helping the environment, getting a better laundry results?
No. More chemicals mean more chemical manufacturing, the use of more raw material stocks, the use of more energy in detergent manufacturing process and transportation.
My proposition, based on the fact that you are constantly heating up the water in the water tank (unless you have an on-demand water heater) is: use hot water (if the fabric allows it) to clean, and use cold water to rinse.
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