Q I am hearing "buzz" about on-demand water heaters. What are the pros and cons of this system?
A The pros for gas on-demand (or tankless) water heaters:
• Generally, they can cut hot water energy use 20 to 30 percent.
• They are small, often mounted on a wall, freeing many square feet of space for other use.
• Most tankless water heaters are designed with a direct vent to the outdoors, eliminating the need for a chimney, increasing the health and safety of occupants.
• A household using natural gas can spend about $250 a year with a standard water heater. An instantaneous one may save $75 to $100 per year at current prices, as well as reduce CO2 emissions by 750 to 1,000 pounds a year.
The cons of gas water heaters:
• They have a large "instant" demand for gas that may exceed your home's gas supply capacity. Most homes have a gas supply -- the capacity of the line coming into the home -- of about 300,000 BTUs per hour. Demand for gas by an existing clothes dryer, furnace, gas grill and fireplace may limit the ability to install a gas on-demand water heater. However, investment in more energy-efficient appliances can make a home more compatible. An energy-efficient front-loading washer, for example, uses a lot less hot water. And it's so efficient at extracting water that operation of a gas dryer is reduced, thereby saving gas. An energy-efficient dishwasher also uses less hot water.
