Most of us grew up with, and still have, a conventional water heater stuck a corner somewhere. It's that silo-like device that heats and holds water until you're ready to hit the hot tap. You probably never think about unless it leaks or breaks down, but it's one of the biggest energy users in your home.
For some homeowners, there may be a more energy efficient and environmentally friendly way to get that hot water virtually whenever you want it.
A tankless heater provides an almost endless supply of hot water on demand while occupying much less space than a conventional water heater with a storage tank, which requires fuel to keep the water always hot and ready to use.
Tankless heaters heat only the water being used, said Mark Whaites, owner of Edward I. Case Plumbing in Tampa. "Therefore, it's being more efficient when it comes to fuel usage. Once it gets to the faucet, you never run out of hot water."
The U.S. Department of Energy estimates gas-fired tankless heaters can save an average family 30 percent on its water heating expenses -more than $100 per year.
There are a variety of models available, but gas tankless systems typically cost about twice as much as conventional systems - from $1,500 to $3,500, depending on the type of unit and installment requirements. Those include a minimum ¾-inch gas line, said John Gennaro, owner of Red Cap Plumbing in Tampa and co-host of a Saturday morning home improvement radio show on WFLA, 970 AM.
Tankless gas heaters are up to 94 percent efficient, Gennaro said, compared to 65 percent for a tank unit. Qualifying non-electric tankless water heaters are eligible for a $300 federal tax credit.
"They've become so efficient in their heating, especially compared to the tank type, that the savings really start adding up," Gennaro said.
As for maintenance, a tankless unit - which should last about twice as long as a tank unit - should be flushed by a professional every year or two to reduce scale buildup.
There are some limits to tankless water heaters. Because the unit provides only as much water as it can heat, homeowners must manage their water use. For example, while three people can take back-to-back-to-back showers and not run out of hot water, most tankless heaters can't handle the supply needed for two showers running at once while the dishwasher is working. Tankless units also require more gas to quickly heat the water, so it's important that only a qualified, licensed plumber install them.
Electric tankless heaters are available, but they work best in limited situations, such as smaller apartments or point-of-use applications such as a sink. Like gas heaters, they require more power when they're running.
To heat 4 to 5 gallons of water per minute, an electric tankless heater might need three 50-amp breakers, Whaites said. "That's a lot of power, especially if you only have 200 amps in your house."
Most homes can be equipped with a tankless heater, though some require modifications to accommodate a venting flue. Larger homes may need more than one unit.
Tankless units are easily repaired, compared to storage units. As a result, fewer tanks end up rusting in a landfill.
"By the time you've dried yourself off, that tank is still trying to catch up," heating more water for the next customer, Whaites said.
"The tankless, though, has switched off, so it's not using as much fuel. As a consequence, there's less carbon dioxide going into the atmosphere, which is good for the environment."