Conventional storage water heaters are widely available in North America, fairly inexpensive, and are about 80 percent efficient. However, they do have some drawbacks. For one, they generally don’t last very long. You can count on replacing your water heater every 10 to 15 years, unless you take steps like those outlined here to ensure a longer life span.

Another problem with storage water heaters is that they use natural gas and propane, two fuels slipping toward extinction. Even electric water heaters have some problems. For one, they rely on an expensive source of energy: electricity. (Electricity is the most expensive means of heating water.)

Perhaps the most significant problem with storage water heaters is that they maintain a large quantity of hot water 24 hours a day, 7 days a week, 365 days a year. Heat invariably leaks out of tanks between uses. This is called standby loss. Standby heat loss must be replaced and one-fifth of the fuel consumed by a conventional storage water heater is used to offset the standby losses.

Many, myself included, believe this system wastes too much energy. It’s a little like keeping your car running in the garage 24 hours a day so that it is ready to use anytime you want. A far better alternative is the tankless water heater.