To use less water, try low-flow fixtures like toilets and shower heads. If you’re still using a conventional storage tank water heater, you might want to consider switching to a tankless water heater. “Everybody’s pretty familiar with the typical storage tank water heaters that keep 40 or 60 gallons of water hot 24/7,” Donahue noted. With a tankless water heater, sometimes called an ‘on-demand’ water heater, water is heated only when it’s needed, when a tap is turned or a dishwasher or washing machine is running.