Question

Do water heater timers work as advertised?

Asked by Stephan Pollard
Fayetteville, AR

I am considering installing a timer on our home's gas-fueled water heater.  I just purchased a home in Arkansas having a relatively new standard 50-gal gas-fueled water heater storage tank. I am hoping to significantly decrease CO2 emissions and lower the gas bill without having to purchase a very expensive alternative system.

Answer

Stephan,

Unfortunately marketing hype seldom delivers on its promises. 

Shutting off a gas-fired water heater for a period of time when you aren’t using hot water will not result in much energy savings.

Baseline heater efficiency

You mentioned that you have a relatively new standard water heater. I am assuming this is a gravity draft water heater rather than a fan assisted.

  • The gravity draft water heaters are around 50-54% efficient while the fan assisted models range from 10 – 14% more efficient.
  • You didn’t mention tank size but that plays a role in efficiency too, the larger the tank the greater the heat loss (more surface for conduction).
  • Gas-fired, tankless, on-demand water heaters offer efficiencies in the 80 – 96% range.

Improving water heating efficiency

Let’s look at some options to saving energy with respect to water heaters that do not involve installing a timer or replacement of the appliance.

Blanket. Install an insulation blanket on the water heater. Adding a layer of insulation will reduce the temperature difference (Delta T) between ambient air and the water heater.

  • The lower the Delta T the lower the heat transfer rate (from hot to cold).
  • Insulation blankets are available at most big box stores and are easily installed by a handy homeowner.

Pipe insulation. Insulate all (accessible) hot water lines. Adding preformed pipe insulation (either fiberglass or foam) to hot water lines helps reduce line loss, keeping hot water in the pipes for up to 30 minutes longer than uninsulated pipes.

Cold water insulation. Insulate the first 6-feet of cold water line (to the water heater) at the top of the tank. Again this is a job for a handy homeowner. Make sure you do not install foam insulation too close to the water heater flue pipe or draft hood.

Low flow fixtures. Reduce your use of hot water by replacing shower head fixtures with low flow (1.75 GPM) replacement heads and lavatory faucets with flow rates of 0.5 GPM.

Turn it down. Set your water heater at 105-degress. It takes less energy to maintain 105-degrees than it does 120- degrees plus it is safer (less of a scald hazard).

Flush your water heater monthly to remove mineral deposits from the bottom of the tank. Note that many newer water heaters are self cleaning so check your homeowner manual.

  • Flushing 1 – 2 gallons of water monthly from the water heater drain valve will remove mineral deposits from the bottom of the tank.
  • If deposits are allowed to build up they will insulate the tank from the burner making it more expensive to heat water.
  • Tanks that “gurgle or percolate” already have a buildup in the tank and should be candidates for replacement if flushing doesn’t solve the problem.
  • A word of caution, make sure you have a hose Bibb cap handy in case dislodged mineral deposits prevent the drain valve from closing fully allowing the valve to drip slowly. Caps are available at your local hardware store for around $1.

If it sounds too good to be true

Effective energy savings are rarely about gimmicks or expensive investments.

Conservation is the most effective energy savings option we can take.

When making purchasing decisions always look to products that offer reduced energy and water use to continually lower your energy use point.

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