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Standard Hot Water System Energy Savings

In a typical American home the water heater uses more energy than any other appliance in the home except for the heating system. Depending on local energy prices, it costs a typical family of four between $200 and $500 per year for water heating. For many families, this represents a significant portion of their utility bills.

For most households, the energy used to heat water can be reduced by 25-50 percent through conservation. This amounts to a savings of approximately $50-$250 per year at current rates. This web site offers many tips for reducing hot water usage. Here are some tips for increasing hot water energy efficiency.

Increasing Water Heating Efficiency

Set Back the Water Heater Thermostat
Some states now require that all new water heaters be set at 120°F at the time of sale. This increases the safety and energy efficiency of the heater.

If your water heater was purchased prior to 1984, it's likely that the thermostat is set higher than this, probably between 140°F and 150°F. You should set it back if this is the case. Most people shower at a temperature of 105°F, so a setting of 120°F will still require mixing with cold water for a comfortable temperature.

Hot water temperatures greater than 120°F are not necessary and should be reduced for several reasons:

  • It can cause scalding. Children and seniors are most often scalded. Scalding occurs in: 2 seconds at 150°F, 15 seconds at 140°F, 30 seconds at 130°F, 10 minutes at 120°F

  • It causes the water heater to lose heat at a much greater rate than would occur if the temperature was kept lower; and

  • It increases the rate of corrosion on internal fittings and other surfaces.

By lowering the thermostat from 150°F to 120°F, energy demand is reduced by 15 percent.

Insulate Your Water Heater
Older water heaters lose heat quickly because they contain only an inch or two of fiberglass insulation (R-5). To reduce heat loss, they should be wrapped with additional fiberglass insulation.

Insulating kits can be purchased at home supply and hardware stores, and some electric utilities will install them at no charge for customers. Most have an insulating value of R-11 and will save $20-$28 per year at current rates.

Rigid foam board insulation placed under the water heater can further reduce heat loss. About two inches of extruded polystyrene board is recommended since it resists compression and does not absorb water.

Gas water heaters should be wrapped with insulation specifically made for gas water heaters. These kits are designed so that they won't block the air intake and insulation will not come in contact with the flue. This is essential for proper functioning of the heater and to avoid a fire hazard.

Insulate Pipes
Your house is a good candidate for pipe insulation if you use water frequently throughout the day, if the pipe runs are long, or if they pass through an insulated crawlspace or basement. It is necessary to wrap hot water pipes only. Pipe insulation comes in different forms:

  • Closed-cell flexible foam tubes (R-3 to R-5);
  • Rigid foam (R-7); and
  • Fiberglass batts (R-11).

Other Water Heating Alternatives
If you have already taken basic hot water conservation measures and seek further reductions of your hot water bill, other water heating alternatives may be considered. These include tempering tanks and demand water, heat pump, solar, and wood-fired water heaters. In general, these systems are most cost-effective in new homes or for families using greater than average quantities of hot water.

Anti Convection Valves
If the hot and cold water outlet and inlet run vertically up from the water tank, convection up these pipes causes heat loss when the tank is not being used. To reduce heat loss, anti convection valves, essentially tiny ball check valves, can be purchased at plumbing outlets and installed on both the inlet and outlet of the water heater. You may need a plumber to install them for you. If so, wait until other plumbing work needs to be done. This will save on costs.

Water Heater Timers
Timers are not very effective at reducing energy use unless time of use (or "peak") rate structures are in use. Also, if the tank is well insulated, the savings from timers will be relatively small. A water heater timer might save 36 kWh (or $1-$2) per year on a well-insulated water heater. Tank insulation wraps, because they are simpler, less expensive and more effective, are a preferable means of saving energy.

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