This article was originally published in the September/October 1996 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online September/October 1996
Average Rates Rate a Complaint Here in the western United States we also have a problem with average electric rates. (See Where Do Average Costs Come From? Letters, HE July/Aug '96). The average residential rate for our customers is only 6 cents/kWh. The problem is that energy-saving products often show cost and payback information based on higher rates. When customers don't see the promised reductions on their bills, we hear about it. Packaging should include payback calculations for several rates, so customers everywhere could have accurate information. Thanks for the great magazine! Carol Dollard
CEM Energy Services Coordinator
City of Longmont Electric Department
Longmont, CO Call the COPs-HE Unfair to Heat Pumps! Your March/April '96 article Choosing a Heating System That Saves Energy (p. 27) underscores the difficulty of comparing HVAC technologies. A focus on heating alone doesn't do the comparison justice, when you consider that heat pumps don't just heat. Further, the article is inaccurate and always tilts toward favoring gas.
The author says that one divides the HSPF by 3.413 to get a heat pump's seasonal Coefficient of Performance. By this figuring, an air source heat pump just in compliance with US standards (HSPF of 6.8) will have a COP of 1.99. Many air source units have significantly higher ratings than this. Yet in Table 2 (p. 30) the article claims that the typical seasonal efficiency of an air-source unit is 150% (COP of 1.5). Why not provide a range of efficiences, starting with the legal minimum, as you did with just about every other technology?
Even worse, the article puts the typical seasonal efficiency of a ground source heat pump at 260% (COP of 2.6). Again, this is about the absolute worst one can do with this technology on a seasonal basis. Most units sold have COPs well over 3, under an ARI test regime that measures not seasonal, but winter peak performance. A 1993 EPA report found that standard ground source units with single-speed reciprocating compressors operated at a seasonal efficiency of 275% or better in the coldest U.S. climates, even taking into account the air handlers! In warmer climates, seasonal efficiencies weighed in as high as 500% for the best systems.
The panel Integrated Systems for Space and Water Heating mentions only gas systems, neglecting to mention integrated air- and ground-source heat pump systems that provide full-demand water heating. You also never mention the fact that most ground source systems are installed with desuperheaters, which can provide 15%-40% of a home's water-heating, essentially for free. Ground source systems also heat water while cooling the house.
Geothermal Heat Pump Consortium Incorporated
You make a good point about heat pump desuperheaters used to heat water. They were left out of the section on integrated space and water heating systems by an editing oversight, but are an excellent application and improve the economics of heat pumps. I agree that cash flow calculations can be beneficial in convincing people to purchase efficiency measures, especially expensive ones like ground source heat pumps or even high-efficiency condensing furnaces. However, simple payback calculations are still useful for quickly comparing with other options.
Editor's note: Look for an article on ground source heat pumps in the next issue of Home Energy.
Locating replacement anodes can be as challenging as removing them from tanks. Usually all you'll get at hardware stores is a quizzical look. Even plumbing wholesalers may not have the anode you need. These mail-order sources should be able to supply you:
Gull Industries. Tel: (800)748-6286
We have seen no firm figures on recirculation system energy use and believe there are too many variables to make such figures very useful. Minimizing the time hot water is in piping reduces opportunity for heat to escape, and the Metlund system addresses that need well. Next best would be a thermostat- and timer-controlled system.
Home Energy can be reached at: email@example.com
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