Detergent chemists have come a long way since Fels Naptha and boiling water was the answer to dirty laundry. Most people still think hot or warm water gets clothes cleaner, but in fact all it does is add cost. Consumer Reports calculates you could save enough in energy costs to pay for 300 loads worth of detergent. Your clothes will last longer, too. Warmer water contributes to fading and can cause fabric shrinkage. Save the hot water for your shower.