Storage type water heaters have long been the most popular type of residential water heater. A conventional storage type water heater keeps a tank full of water hot for use when needed. Despite their popularity, storage water heaters waste energy due to standby heat loss and waste water when the tap has to run for a period of time before the hot water reaches the tap.
In an effort to address these concerns, many homeowners have converted to demand (or tankless) water heaters that only heat water when it is needed and can produce instant hot water if installed at every tap, but the conversion from a conventional storage type water heater to a demand water heater is expensive and demand water heaters have a few disadvantages that detract from the allure of instant hot water.
Sticking with a storage water heater offers the lowest up front cost and by choosing a properly sized energy efficient unit, your operating costs will not be a lot more than with an on-demand system. The primary way that storage water heaters waste energy is through standby heat loss. Energy is wasted by keeping the tank of water hot even when there is no demand for hot water.
You can minimize standby heat loss by looking for a water heater with a heavily insulated tank. Thermal resistance is measured by R-Value and the higher the R-Value, the better insulated the tank is and the less energy that is wasted on standby heat loss. Look for a minimum R-Value of R-12 and a higher R-Value would be better. Some water heaters have thermal resistance of up to R-25.
