Water Heaters: To Insulate or Not? More Ways to Save!

When considering all the ways to cut energy costs, no plan should be without an evaluation of your home's water heater. According to the Department of Energy (DOE), Americans use 15 to 40 gallons of hot water per day per person. That means a family of four may be potentially heating up to 160 gallons in any 24 hour period. DOE data also suggests that 15% of our annual electric costs and 25% of natural gas expenditures is attributible to water heating.

Water heaters consume energy in three basic ways: demand, standby, and distribution. Demand is defined as the energy used for heating incoming cold water up to the temperature setpoint. Standby is defined as the heat lost through the storage tank's walls while waiting to be consumed. Standby losses can account for anywhere from 20% to 60% of total water heating energy consumption. Houses using less hot water will still have standby losses, proportionately higher. Distribution loss is the heat escaping through pipes and fixtures once the water has left the tank and now resides in between the tank and the fixture endpoint.

The majority of water heaters in single family homes in the United States today are defined as direct storage water heaters. This means they combine the heating device, heat exchanger, and storage tank into one unit. 

Understanding then how heat is lost from your direct storage heating appliance and associated piping will go a long way in identifying those areas where you can make simple adjustments.

Consider these points when evaluating the prospect of insulating your water heater:

• What is the age of your water heater? Locate the serial number on a label at the front of your heater. The year of manufacturer is generally found within the first four digits. Any water heater manufactured before 1991 would probably benefit from additional exterior insulation. After 1991, check with your manufacturer. Obviously, newer is more likely to have increased insulation.
• Water heaters manufactured prior to 1991 were insulated with fiberglass and typically have a thermal resistance (R-value) of R-3 to R-6, while newer models will range from R-7 to R-25 and are insulated with polyisocyanurate insulation.
• Can't determine the age? Remember most water heaters are designed to last from 8-12 years for gas, and 10-15 years for electric. Also, just feel the exterior of your water heater. Is it noticeably warm?  If so, you may have an older model and could benefit from additional insulation.
• Before running out to the store to buy your new insulated blanket, do a little research on your particular make and model. Some manufacturers of newer direct storage water heaters may void any warranty in place since testing of their appliances for UL approval was not done under those same conditions your appliance will encounter in your home.
• Insulating jackets are easily available at most home improvement stores. Talk to the associate about size, type (gas or electric), and R-factor.
• Use caution when insulating the water heater, as there are areas that cannot be covered for operational and safety reasons; the warning label, top of the water heater (gas vent), the temperature pressure relief valve, access panels, bottom air inlets (gas) should all be visible and easily accessilble.
• Insulate copper supply piping, hot and cold, with polyethylene or neoprene foam. Rule of thumb is first 6 feet of cold water supply coming into the tank and all accessible hot water supply lines. Match the insulation wrap inside diameter with water piping outside diameter for a snug fit, and secure every few feet with acrylic tape, wire, or cable tie.
• Lastly, revisit your thermostat setting. Now that you've insulated, you may be able to reduce it a couple of degrees, staying above 120F degrees.

In summary, older water heaters are more likely to benefit from blanket wraps than newer. Insulation is relatively inexpensive and costs will be recovered in a relatively short amount of time. Determining the age of your particular heater is the first step. If the water heater's exterior temperature is 10F degrees higher than surrounding room temperature you're probably wasting energy. And lastly, we can all benefit from insulating our supply piping, if not already in place.

Keep in mind this isn't your typical do-it-yourself project.  When in doubt, always consult with a licensed professional.