On GFX and Electric Water Heating

Thank you for recognizing the GFX drain water heat recovery system in “Recovering Heat from Wastewater” (EBN

Vol. 6, No. 8). As stated in your article, this exciting new product has the potential to improve the hot water delivery performance of domestic water heaters while reducing costs and energy use. This potential has been confirmed by laboratory testing sponsored by Virginia Power and should be demonstrated by a planned NAHB Research Center field test.

I was disappointed, however, to see included in your article on this efficient new device, developed by the electric water heating industry, the inaccurate and misleading statements attacking electric water heating. You characterized electric water heating as inefficient and limited in the amount of hot water it can provide. You concluded that, even with GFX, electric water heating is not recommended “given the overall pollution and primary energy consumption.” These statements, although often repeated, are not well founded.

Your article is correct in asserting that one of the main benefits of GFX is its ability to “keep you from running out of hot water.” However, frequent hot water run-outs are caused by improper sizing of the hot water system, not the energy source used to heat the water, as implied by the article. Because of its ability to increase the amount of hot water delivered by a water heater (i.e., effectively increase first-hour rating), the GFX can be used to correct situations where water heaters have been undersized without replacing the water heater and while saving energy. It can also be used to reduce the size of electric water heater required for an application where cost, available space, venting or safety of combustion sources are constraints.

Regarding efficiency, it is well known that electric water heaters typically have energy factors 30% to 60% higher than fossil-fueled water heaters used in similar applications. Testing sponsored by Virginia Power at Old Dominion University has found that the GFX effectively increases the energy factor for electric water heaters by about 57% to 73%. (Fifty-gallon electric water heaters demonstrated effective energy factors of 1.17 to 1.82 in this testing.) Although actual performance will depend on the amount of hot water used in flow applications, these effective energy factors with GFX on electric water heaters can result in typical primary energy use for electric water heaters comparable to natural gas-fired units. If fuel scarcity and diversity are also considered, electric water heaters, particularly those used with GFX, have a distinct advantage over fossil-fired units in their use of energy resources.

For a utility with a generation mix similar to Virginia Power’s, this also means that carbon dioxide emissions from electric water heaters using GFX are similar to those of gas-fired water heaters, and carbon monoxide and VOC emissions are significantly less than those of gas-fired systems. In addition, emissions from electricity generation are constantly monitored and controlled while emissions from on-site appliances can vary widely depending on age and maintenance.

With the coming of electric utility deregulation, consumers will have increased choices in the source of their electricity and may choose to purchase electricity generated from renewable energy or other low-emissions sources. In this case, electric water heating will provide consumers with greater opportunities than fossil-fueled appliances to minimize the primary energy use and emissions resulting from water heating.

GFX can provide a variety of benefits when used with electric water heaters. Its use should not be limited by the bias held by some against electric water heating.

Timothy A. Bernadowski, Sr., P.E. Virginia Power

Richmond, Virginia

Editor’s Response:

Thank you for reinforcing the value of the remarkable GFX system. You make a number of important points and a few that call for rebuttal or clarification. First, it’s important to note that the energy factor that you mention considers only energy delivered to the building, not the inherent inefficiencies of electricity generation and transmission. As you point out, typical primary energy use for an electric water heater with the GFX is comparable to that of a natural gas heater without the GFX. We simply made the point that a better option would be a gas heater with GFX. And while the CO2 emissions for your utility may be relatively low, those in more coal-intensive regions are much higher.

We share your hope that deregulation will lead to an increase in electricity generated from renewable sources, but there remains the distinct possibility that deregulation will result in more electricity from more polluting fuels, such as coal. And for water heating, direct solar water heaters would seem to make a lot more sense.