7 No Cost Ways to Save Reduce hot water temperature to º. Save 7-11 % of water heating costs. Insulate water supply line (first 5 feet). Use cold water when washing clothes % of home energy cost is for water heating (today s detergents are designed for cold water). Clothes dryer: Keep dryer free of lint (clean filter every load). Keep dryer vent free of obstructions. Do not vent into the house or attic.