Every minute of every day, your standard water heater keeps 40 to 80 gallons of water heated to 120 degrees or higher, even when you're asleep or playing with the dog or not even at home. Small wonder that the cost of heating that water is a home's second- or third-biggest energy expense, representing 13% of a typical utility bill. A "tankless water heater" - also known as a "demand water heater" or "instantaneous water heater" -- can help pare the cost, as well as the environmental impact.
A tankless water heater provides hot water only when needed. It heats water on demand. How it works: You turn on the hot water tap, the system rapidly heats cold water (which travels through a pipe into the unit), and hot water flows to your tap as long as you'd like. That means you won't run out of hot water in the middle of a shower.
For homes that use 41 gallons or less of hot water daily, a demand heater can be 24% to 34% more energy-efficient than standard water heaters, according to the US Department of Energy. If your household uses lots of hot water - say, 86 gallons daily - the savings are smaller; a tankless water heater can be 8% to 14% more energy efficient than a standard version. Energy savings can reach 50% if you install a tankless heater at every hot water outlet. (See: www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=12820)
Tankless water heaters cost more up front than standard models; the idea is that you'll save money in the long run due to lower energy bills. That's why they're appearing in some high-end houses, zero-energy homes and even some Habitat for Humanity houses, such as a project in West Philadelphia (see tinyurl.com/36u9yw). If your old storage water heater is on its last legs and you opt for a tankless unit, check whether you can get a federal tax credit. At least in 2007, homeowners who chose an eligible model (a gas unit with an Energy Factor of 0.80, or an electric unit with an EF of 0.2) could get a $300 federal tax credit.
For more info:
Tips on saving money on water heating from the US Department of Energy:
9 Best Practices for Choosing and Installing a Tankless Water Heater:
How Do I Choose a Tankless Water Heater?:
Some plumbers love them, others don't:
Enter your city or zip code to get your local temperature and air quality and find local green food and recycling resources near you.