Reducing hot-water usage is primarily a matter of common sense and exerting a little extra effort to not be wasteful. Once you have applied a few simple, low-cost measures for reducing hot-water consumption, you may want to consider water-heating system improvements if you wish to further reduce your energy bill.
Lower Your Water Heater Thermostat
One simple step for reducing waterheating energy costs is lowering the thermostat setting on your water heater. Although some manufacturers set water heaters at 140°F (60°C), 120°F (48.9°C) is satisfactory for most household needs. Furthermore, when heated to 140°F, water can pose a safety hazard (i.e., scalding). For each 10° F (5.6°C) reduction in water temperature, water-heating energy consumption can be reduced 3% to 5%.
If your dishwasher does not have a booster heater, lowering the water-heating temperature is not recommended. Also, many dishwasher detergents are formulated to clean effectively at 140°F and may not perform adequately at lower temperatures. (See previous discussion on Automatic Dishwashers.)
On gas water heaters, thermostats are usually visible. Electric water heaters, on the other hand, may have thermostats positioned behind screw-on plates. As a safety precaution, shut off electric current to the water heater before removing the plates. Keep in mind that electric water heaters may have two thermostats to adjust—one each for the upper and lower heating elements —and adjusting these is tricky. Talk to your local water-heating professional for help with this.
When you plan to be away from home for an extended period of time (at least 3 days), turning the water heater thermostat down to the lowest setting, or even turning the heater off completely, can help you achieve additional savings. Be sure you know how to relight the pilot light on your gas heater, though, before you turn it off.
Unlike dishwashers, washing machines do not require a minimum temperature for optimum cleaning.
Setting the thermostat on your water heater to 120°F, which is sufficient for most household needs, is an energy-saving measure you may wish to consider.
Install a Timer and Heat Traps
Another possibility for electric water heaters is installing a timer that can automatically turn the heater off at night and on in the morning. At a $30 selling price and a do-it-yourself installation, a simple timer may pay for itself in energy saved in about 1 year. More expensive, multisetting timers are also available. Timers for gas water heaters are not as useful or cost effective as those designed for electric water heaters. This is because the pilot light supplies some heat during the night, offsetting some of the energy savings achieved by using the timer.
If heat traps were not initially installed with your water heater, adding them is another way of reducing water-heating energy loss. Heat traps, or one-way valves, allow water to flow into the tank and prevent unwanted hot-water flow out of the tank. Heat traps cost about $30, but they may require professional installation, which could be expensive. However, if installed at the same time as a new water heater, heat traps are much more cost effective. Most new water heater models have factory installed traps, saving you the time and expense of installing one yourself.
Insulate Hot-Water Pipes and the Storage Tank
When you turn on a hot-water faucet during cold weather, it may take several seconds for the water to become hot. This happens because the water travels through pipes from the water heater to the faucet, and some of the pipes may pass through unheated sections of the house, such as the basement. As a result, the hot water loses some of its heat to the surrounding space.
This heat loss can be reduced by insulating hot water pipes wherever they are accessible —especially in unheated areas. Use quality pipe insulation wrap, or neatly tape strips of fiberglass insulation around the pipes. Eventually the water will cool, but it will remain warmer much longer inside insulated pipes.
Insulating your water-heater storage tank is a fairly simple and inexpensive improvement that can help maintain the water temperature at the thermostat setting. Some newer models of water heaters are well insulated and do not need an added layer, but a heater that is warm to the touch needs additional insulation.
Easy-to-install, pre-cut blankets (or jackets) for electric water heaters are widely available and range in cost from $10 to $20. Your local utility company may offer them at a lower price, give you a rebate, or even install them at no cost. When properly installed, a water heater blanket on an electric water heater will pay for itself in energy saved within 1 year. Installation is more difficult on gas- and oil-fired heaters. Ask your local furnace installer for instructions.
If your water heater is at least 7 years old, you should carefully evaluate your waterheating needs and investigate the types of heaters that could replace your current one. Although most water heaters last 10 to 15 years, early investigation and timely replacement can ensure a wiser purchase.
This document was produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory (NREL), a DOE national laboratory.