Water Heaters


Heat Pump Water Heaters help End the Need for Natural Gas – Complement Solar Panels

This website advocates the use of heat pump water heaters. Far more efficient than regular electric water heaters, heat pump water heaters can replace natural gas water heaters and reduce our dependence on fossil fuels. For a list of high efficiency heat pump water heaters, their manufacturers, and their performance, click on this site of listed qualified vendors under the Northwest Energy Efficiency Alliance advanced water heater program. Note that the list now includes natural refrigerant, ultra-high efficiency CO2 heat pump water heaters manufactured by Sanden.


This technology is a wonderful complement rooftop solar. Several brands are available and the incentives offered by utility companies and government tax credits can make these products a relatively low priced alternative compared with other options. However, there are a few things you must keep in mind when you consider buying one. First, they draw heat out of the surrounding air, so placing them inside a small house or small room doesn’t work well. They should  be situated in a large space, like a garage. Also, the heat pump in these units creates a small amount of water condensate that needs to be drained or piped away. The heat pump is normally at the top of the water heater, so the condensate often can be naturally drained through a sloped plastic pipe to a drain or to the outside of the building. When these units are operating they make a low but audible noise, about like the noise of a microwave oven. If you’ve got a garage where you can situate the w/h, then it can be a terrific way to reduce your water heating costs, have the full convenience of a tank water heater, and leave natural gas water heating behind.

The Bonneville Power Administration has done extensive testing on heat pump water heaters. The BPA’s research strongly supports the conclusion that widespread adoption of this technology is achievable, affordable, and a key component to energy conservation and green house gas reduction. See their website here:

Some of the  main brands of water heater include GE’s “Geospring,” Voltex by AO Smith, Bosch, and Rheem. With tax incentives and utility rebates, some models are very inexpensive indeed. Pricing is competitive with on-demand systems and the payback period for these water heaters is often less than five years.

The Bonneville Power Administration, the government agency that manages the hydroelectric power in the Pacific Northwest, performed tests on various brands of heat pump water heaters. Their results suggest that the unit made by AO Smith, the Voltex model, is especially efficient and is likely worth the higher price it commands. Note that the “COP” or coefficient of performance, is an indicator of the water heater’s efficiency, and thus an indicator of how much energy it takes to heat your water compared to other water heaters. Take a look at this chart from the BPA’s study. It appears to show that AO Smith’s Voltex model performs in a superior fashion.


One more thing. Notice how the efficiency of the water heaters improves when it operates in warmer air. for this reason, the installation of an inexpensive flexible duct and duct fan can provide warmer attic air to the inlet duct of the water heater. Attics are typically 20 or more degrees warmer than a garage for much of the year, so by supplying warm attic air to the water heater the water heater efficiency can improve significantly. Attic air temperature should not exceed the air temperature limits set by the manufacturer. Also, you must have attic air that is clean and does not pose a health hazard of any sort. If you supply air from a warm source through a duct you must make sure that the duct line is large enough to keep your water heater from being starved for air and also avoid air condensation in the line that could damage the water heater. The addition of an inexpensive duct fan can help ensure that the air supply is always positive to the water heater. Note that if you utilize air from your garage, the air should be exhausted into your garage as well. No air from your garage should ever be vented into the living structure of your house, as auto exhaust is deadly.

See the entire BPA study at this website:


For a full description of heat pump water heaters visit this website:


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