What is COP?

The Electric Cooperatives of Arkansas are very excited about the General Electric Hybrid water heater, or GeoSpring. Why?

Because rarely does a new product come along that actually performs as well as advertised and is feasible, as well as good for consumers. The cooperatives are long-time advocates of energy efficiency and have watched many so-called miracle products come and, mostly, go. There have been the magic black boxes, the many different room heaters, the unbelievable sheets of aluminum foil, and others. There are individual cases where these products may actually help, but almost never perform at the advertised 30, 40, or 50 percent savings.

The GeoSpring will perform exactly as advertised. A couple of commonly asked questions are: “What is the price?”and “How can it be 200 percent efficient?”

Call your local electric cooperative for the current price and here is the answer to the efficiency question.

The engineering term that is used to state the efficiency is “coefficient of performance” or “COP.” I like to say that the “COP” tells us how efficient the product converts a unit of electricity to heat. Here are three examples.

1.      As you try to move electricity through a metal wire it meets resistance. In some metal coils the resistance is so great that the coil glows red hot. You would recognize this in a toaster, a hair dryer, some electric room heaters and in an electric furnace. Most electric heaters have a COP of 1.00 or an efficiency of 100 percent. One unit of electricity in and one unit of heat out.

2.      A heat pump is totally different. It uses a compressor to move heat from one location to another and it does it at higher efficiencies. Think of your refrigerator as the compressor runs and takes the heat out of the milk and puts that heat in the kitchen from the back of the refrigerator. The COP of a properly installed heat pump is about 2.5 or about 250 percent efficient at 40 degrees or warmer. One unit of electricity in and 2.5 units of heat out.

3.      A geothermal heating system has a COP of about 4.00 and one model has a cop of 5.00. One unit of electricity in and 4 or 5 units of heat out.

Gas water heaters do not have COP ratings because they are not electric. They have an Annual Fuel Utilization Efficiency (AFUE) rating. The AFUE rating of most gas water heaters is 57 percent or less. That simply means that about 43 percent of the gas goes straight up the flue to the sky above.

The cooperatives believe that the GeoSpring will deliver hot water at more than 200 percent efficiency.

Go to: www.ecark.org to learn more.

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