Most of the energy efficient advancements that eventually make it into our homes are born in Europe. This is true for tankless water heaters, which have been common there since WWII yet are only now really taking off in the US. The reason for their popularity is a deceptively simple flaw in the way your existing water heater works. A traditional, tank-type hot water heater constantly uses energy to keep water hot and at the ready anytime you might need it. Your family may be large enough to use a good bit of the 50 gallons in a typical hot water heater at 8am on a weekday, when everyone is showering and getting ready for work and school. But a few hours later, when the house is empty, that water heater still consumes energy as it keeps the water at 140 degrees.

Tankless water heaters, as you might have guessed, don’t have a tall, round tank that holds hot water. Instead this appliance hangs on the wall in a mechanical room or closet and is designed to save energy by heating only the water you need when you need it. Inside this efficient unit is a high-powered gas burner that heats water quickly, as soon as its valve senses the call for water. Once you shut the faucet, the burner flame shuts down and the unit waits until it’s called upon again. Until recently this technology was shunned in the US for fear that it could not produce a steady stream of hot water, but that’s changing.

Manufacturers of tankless water heaters cite energy savings of 30 to 50 percent, saving the average family about $100 per year. Even the most energy efficient traditional water heaters have an energy factor of about .67 out of 100, while newer tankless models reach about .95 energy efficiently. A properly sized model, based in part on the number of people in your family, can provide enough water for the entire family; up to 5 gallons per minute, which is plenty for normal demands. Tankless water heaters cost about 40 percent more up front, but you can expect one to last about 20 years, as opposed to 15 for a traditional water heater.

Sounds like a great idea, but the tankless might not be for everyone. For starters, they run on gas, not oil, so your house would need to be plumbed for gas or have propane. Also, if your family has multiple showers going at the same time, while a load spins in the washing machine and dishes are in the dishwasher, a tankless water heater may struggle to keep up with demand. Switching to a tankless water heater is a fairly straightforward installation but it does require a competent technician. Your local plumber may not be up for the task.