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Storage Hot Water Heater Basics

Storage hot water heaters can use a variety of fuel sources (including natural gas, propane, electricity, and even wood) to heat water in a storage tank to a given temperature. Hot water from the top of the storage tank is then ready for use when called for at a faucet. The efficiency of these units is measured by a value referred to as an Energy Factor (EF), listed on the hot water heater label. An EF of 0.65 indicates a high efficiency conventional gas-fired unit, although gas-fired units that use the gases created through fuel combustion to heat more water—called condensing units—can have EFs of 0.86. An EF of 0.95 indicates a high efficiency electric unit, although new electric heat pump water heaters can have EFs above 2.0 as they remove heat from the surrounding air or from the ground to heat water in a storage tank. Keep in mind that the higher EF for electric water heaters does not account for the efficiency of the power plant used to generate the electricity. In addition, the current high cost of electricity relative to natural gas can make even the highest efficiency electric storage units more expensive to operate than some natural gas storage hot water heaters. On the other hand, electric appliances do not require combustion inside the home, which limits fire risk and potential health hazards.

Storage Hot Water Heater Limits

One of the limits on the efficiency of storage water heaters is that the water in the storage tank gets heated to a set temperature even if the water isn’t being used. The efficiency loss associated with this characteristic is called ‘standby loss’. Standby loss can be minimized in storage tanks that are well insulated, with R-values as high as R-25.

Other Things to Consider Before Buying a Storage Hot Water Heater

As with all types of water heaters, it is important to properly size a new unit instead of simply purchasing the same size water heater as your existing unit. Hot water conservation can result in the need for a smaller unit, can save you money on your purchase, and can save you money when the unit operates. To properly size a storage hot water heater, you need to estimate the maximum amount of hot water your household would use in a one hour period (called ‘peak hour demand’).

Maintenance for storage hot water heaters may include periodic water flushes from the storage tank, checking pressure and temperature valves, and other manufacturer recommendations.

Last updated: October 18, 2017 at 10:48 am