Electric water heater schematic (C) Carson Dunlop Associates

Hot Water Heater Timer Recommendations for Energy Savings
     

  • TIMERS for ELECTRIC WATER HEATERS - CONTENTS: Water heater timers: how to choose and use a water heater timer to save energy
    • Guide to inspection of electric water heaters
    • Timers for electric water heaters
    • Timers for tankless electric water heaters
    • How long should the "off" time be on an electric water heater for a timer to save energy
    • Comparing savings from water heater timers with other options
  • POST a QUESTION or READ FAQs about how to install, set, use, and troubleshoot electric water heater timer controls
  • REFERENCES

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Guide to water heater timers for energy savings: this article explains how discuss the use of timers to control electric water heaters and tankless electric water heaters. This article contains links to in-depth articles on inspecting, testing, and repairing problems residential hot water heaters of all types, including their parts, controls, and alternative sources for hot water as well as tips for improving hot water temperature, hot water pressure, and hot water quantity.

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Guide to Using Timers on Residential Hot Water Heaters

Water heater timer control (C) Daniel Friedman

The sketch above shows the basic components of an electric water heater and is provided courtesy of Carson Dunlop Associates.

This article contains links to in-depth articles on inspecting, testing, and repairing problems residential hot water heaters of all types, including their parts, controls, and alternative sources for hot water as well as tips for improving hot water temperature, hot water pressure, and hot water quantity.

 

Also see Energy Efficient Water Heating, a US Department of Energy, a PDF file that provides tips on lowering your water heating bill.

 

 


Water heater timer control (C) Daniel Friedman

The link to the original Q&A article in PDF form immediately below is followed by an expanded/updated online version of this article.

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Water Heater Timers

Question:

Does it make sense to put a timer on an electric hot water tank to turn it off for most of the day if no one will be home?

How about using a timer on a tankless electric water heater if gas is not available? -- Bill Geary, Belfair WA

Answer:

Efficiency of Timers on Conventional Electric Water Heaters

According to Princeton Energy engineer Gautam Dutt, the idea of using a timer on an electric water heater will work fairly well if your daily hot water consumption is less than one water-tank load, or if the hot water heater will be shut off for several days at a time, such as over a long weekend.

For shorter time periods or for higher hot water consumption rates, in the 1980's Dutt thought that it would be more practical to insulate the water tank.

However modern hot water tanks come from the manufacturer with good insulation, and in some cases insulating a hot water heater tank may fail to follow the manufacturer's instructions, could void its warranty, or could make the water heater unsafe (if for example you covered the pressure-temperature relief valve). --DF

In the 1980's a typical stock electric water heater was about 73-percent efficient, including tank losses. If you included hot water delivery piping losses, the efficiency of the water heating system drops to about 60 percent. This is a good incentive to add insulation on your hot water piping, and it may help you decide on using a water heater timer too.

At WATER HEATER EFFICIENCY we provide a comparison of the efficiency of different types of water heaters.

What is the Energy Efficiency of Electric Tankless Water Heaters?

Tankless water heater (C) Carson Dunlop AssociatesDutt said that tankless electric hot water heaters work best if the hot water demands are low, and if points of hot water use are clustered in the building (as opposed to having the tankless water heater deliver hot water through long pipe runs to distant points of use from the heater itself).

Obviously this is easier to achieve in new construction than in a hot water heating retrofit.

We add that because tankless water heaters have zero or very low stand-by losses, there would be typically be no gain achieved by installing a timer on an electric tankless water heater. -- DF

Drawbacks of electric tankless hot water heating systems are that they draw high electrical current (amperage) and supply low hot water flow rates. This means that from a modest-sized tankless electric hot water heater system you can't shower and wash dishes at the same time, and low hot water-demand appliances are in order as well.

Consumer Reports points out that a tankless water heater may be efficient but not necessarily economical to operate. What they mean is that it is certainly efficient to avoid heating water when no one is using it. But if water usage is high, a high-BTU tankless water heater may consume more total energy than a large but more conventional oil or gas fired hot water tank and burner.

See TANKLESS WATER HEATERS and Should I Convert to a Tankless Heater? for more about these systems.

Sketch (above) of a point of use tankless water heater courtesy of Carson Dunlop Associates. Our OPINION is that readers looking for plenty of hot water heated efficiently should also consider the heater we describe at Indirect-fired Water Heaters.

Readers should also see ALTERNATIVE HOT WATER SOURCES to distinguish among these types of hot water producing systems and see Electric Shower Heaters for a discussion of point of use heaters at shower heads.

If your hot water is not working, check the water heater timer: Some electric water heaters are installed with a timer (photographs above) that saves electricity costs by turning off the heater during periods when no one will be using hot water. If a timer is installed for your heater, it might be in its "off" position. Instructions for setting the water heater timer are inside the timer cover.

WATER HEATER PROPERTIES discusses water heater types and their efficiencies; there we also note that using a water heater at a high duty cycle (such as heating a home) will shorten its life.

Also see Energy Efficient Water Heating, US Department of Energy, a PDF file that provides tips on lowering your water heating bill.

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