The Steamy Side of Energy Efficiency

A few simple steps can help improve your water heater’s energy efficiency.

If your current water heater has a R-value of 24 or lower, adding a low-cost insulation blanket will help reduce heat losses. R-value information is usually listed on the tank itself or in the owner’s information paperwork. Insulation blankets can be installed on both gas and electric water heaters, however, look over the information on the Energy Star’s webpage for specific instructions in each case.

An 80 gallon tank with R-16 insulation will waste around 30 kwh per month in heat loss during the winter time (120 degree water, 60 degree attic). In our area, electricity costs $0.13 per kwh, which amounts to losing $11.70 in those months (30 kwh x $0.13 x 3 months). Considering that you can purchase a tank blanket for around $20 from the local home improvement stores, you can recoup your “investment” in two years or so. For more details and information on the calculations shown above click on this link.

Depending on the distance between the tap and the tank, it can take a good while for hot water to reach the faucet. This is because all of the water sitting idle in the piping cools off quickly. Insulating as much of the hot water supply piping as you can reach along with the first 10’ of pipe entering the tank will reduce these losses. Water in insulated pipes stays around 2 to 4 degrees warmer, which means you can also lower your thermostat settings. The added bonus is a shorter wait time for that nice, steamy shower, which saves you on your water bill as well.

Pipe sleeves are available for $1.20 to $5.30 per 6’ length from most home improvement stores. Be sure to match the sleeve’s inner diameter to the pipe diameter to a good fit. Install the sleeve with the seam facing down and seal along the seam with foil (not duct) tape. On gas water heaters, keep insulation at least 6 inches from the flue.
Great articles on heat loss in water pipes can be found at these websites: Water Pipe Cooling and Energy Star.

Insulating the tank and piping means you can also lower your thermostat temperature, since you won’t have to compensate for heat losses. For each 10ºF reduction in water temperature, you can save between 3%–5% in energy costs. Lowering the temperature also slows sediment buildup and corrosion in the tank and pipes.

Electric water heaters have both an upper and lower thermostats which should be adjusted to maximize the convection loop inside the tank. Set the upper thermostat to 125 degrees and the lower one to 115 degrees. Thermostats on electric tanks are usually positioned behind screw-on plates or panels. As a safety precaution, shut off the electricity to the water heater before removing/opening the panels. The thermostat dial for a gas water heater is typically found near the bottom of the tank on the gas valve.

To check that you are getting the correct water temperature, mark the beginning setting and the adjusted temperature on the thermostat dial. After turning it down, check the water temperature with a thermometer at the tap farthest from the water heater. You may need to make a few adjustments before you get the right temperature.

Electric water heaters can save an additional 5%–12% in utility costs with a programmable thermostat. This turns the heating element off at night and back on before hot water is needed in the morning. They can cost $60 or more, but will pay for themselves within a year or two when used with an insulated tank and piping.

The last, but not least, thing you can do so save on the life and efficiency of the water heater is to perform regular maintenance including flushing the tank and replacing the sacrificial anode. The high operating temperature of water heaters encourages the precipitation of calcium carbonate, which settles and builds in the bottom of the tank. In gas-heated tanks, this sediment creates a barrier between the gas burner and the water, which results in longer heating times and lower fuel efficiency. Sometimes the bottom of the tank will overheat, weakening the tank steel and glass lining and reducing the life of the tank. In electric water heaters, the sediment layer can completely bury the lower element, causing it to burn out. This requires the upper element to heat the full tank of water, wasting energy and money.

To drain and flush your water heater, turn off the gas or electrical power and let the water cool down. Close the incoming water valve and attach a hose to the drain valve to run the water into a large bucket, or drain to the outdoors. Open the drain valve, and turn on one hot water faucet somewhere in the house to let in air. When all the water has drained, turn the cold water valve on and off until the water from the drain runs clear. Then close the drain valve and the hot water faucet, open the cold water valve, and turn the water back on.

Tank flushing is also a good time to check the condition of the sacrificial anode and replace it if necessary. Be sure to check your owner’s manual for instructions on the how, what and when for your particular tank’s maintenance.

This blog was written for Paul LaGrange’s BuildWrite website and was originally posted on March 6, 2009.


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