Tankless Water Heaters – An Option for Homeowners

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In days past, taking a hot shower or washing dishes meant that water had to be heated ahead of time and stored, which can be quite inefficient. Now several types of “demand” water heaters heat water, as the household needs it, saving energy, money, and sometimes water itself. Conserving energy not only lowers power bills, but also promotes a cleaner environment.

Two types of water heaters operate without a tank – demand (tankless or instantaneous) water heaters and tankless coil and indirect water heaters. Demand units heat water, as it is needed. When a hot water tap is turned on, cold water travels through a pipe to the water heater where the water is heated over a gas burner or electric element. This supplies a constant flow of hot water, but can be limited by the heater’s flow rate. Demand water heaters generally provide water 2-5 gallons of water per minute.

Sometimes household hot water demands require a back-up demand water heater for additional capacity. Households can also install a separate demand water heater for an individual appliance, such as a washing machine or dishwasher.

Gas versions of demand water heaters provide a higher flow of hot water, but can waste energy if they employ a constantly burning pilot light. With a gas-fired demand water heater, be sure to factor the energy costs for the pilot light into your water heater budget. Also, consider a model that lights the pilot light only as needed. If your home uses 41 gallons of water per day or less, a demand water heater can be 24 percent to 34 percent more efficient than a standard storage tank model. These heaters can be 8 percent to 14 percent more efficient in homes that use 86 gallons of water or more per day. Demand water heaters are usually more expensive than conventional models, but energy savings will offset the higher cost.

When buying a demand water heater, look carefully at the amount of hot water you will need, and look for a high-efficiency model that will save money and energy over the lifetime of the heater.

Tankless coil water heaters use a home’s existing space-heating system to heat water. These units are also called combination water and space heating systems. With a tankless coil heater, when a hot water tap is turned on, cold water flows through a heat exchanger installed in the home’s main furnace or boiler. This type of water heater provides hot water on demand, just as other tankless units do. However, tankless coil heaters operate most efficiently during cold months when a home’s space-heating system is already in heavy use.
When considering a tankless coil or other combination water and space heating system, consult a plumber or heating contractor to determine the appropriate size for your home and hot water needs. Most combination systems are designed for new construction, although some of these systems are available for homes with an existing water heater.

Proper installation of tankless coil or other combination systems can increase energy efficiency and should be done by a qualified plumbing or heating contractor. The installation design should take into consideration fuel type, climate, local building codes, and safety restrictions.

With any water heater purchase, compare the energy factor on water heaters that you are considering; a higher EF means a more efficient heater. Remember,  however, that a higher EF may not mean lower annual operating costs if the heater requires a more expensive fuel. Look for the water heaters bearing the Energy Star label. The Energy Star program identifies products that meet strict energy efficiency guidelines set by the U.S. Environmental Protection Agency and the U.S. Department of Energy.

Source: energystar.gov