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Home Energy Magazine Online May/June 1995
Defrosting Refrigerator Data
We now have a better idea of the energy use of older refrigerators, thanks to utility programs nationwide that pick up second refrigerators. Appliance Recycling Centers of America (ARCA) has been testing the energy use of a sample of collected refrigerators before the units are recycled. Over 1,000 units have been tested in its laboratories during the last two years. The refrigerators were from 5 to 45 years old and their capacity ranged from 2 to 25 ft3. ARCA kindly sorted the data for Home Energy, with the following results.
ARCA first sorted the data by refrigerator type (see Figure 1). As expected, the old frost-free units used the most electricity--about 1,800 kWh per year. Manual defrost models consumed less than half that, and partial-defrost units were somewhere in between. This confirms that the principal target for replacement should be old frost-free units, while replacement of partial-defrost units with new frost-free ones will usually save energy too. Interestingly, 37% of the refrigerators tested by ARCA, a sample of those collected by utility programs, were manual defrost and used an average of 775 kWh per year--about the same as an efficient new automatic defrost model.
Figure 1. Average energy use of refrigerators by defrost system type
There is also nothing surprising about the relationship between refrigerator size and energy use (see Figure 2). The ARCA data demonstrate that smaller units usually use less energy; exceptions appear among the smallest units (where very few units were tested) and the largest units, where 22-23 ft3 models use less than the next smaller cohort. (We can't explain that anomaly in the data.)
Figure 2. Average energy use of refrigerators by size
Finally, ARCA observed the change in energy use over time (see Figure 3). Refrigerators used much less energy 35 years ago because they were typically smaller and manual defrost. The energy guzzlers appeared in the 1970s (like the cars), and improved with federal energy standards over the last decade, with energy usage for a typical new refrigerator at about 800 kWh per year. When an 11- to 25-year-old refrigerator is replaced with a 1994 unit, expect that the house's electricity use will drop about 600 kWh per year. Even replacing a relatively new unit--five to ten years old--should save a few hundred kWh per year (about $30 at 10¢ per kWh).
Figure 3. Average energy use of refrigerators by age.
Taking any refrigerator out of service will save energy if it is not replaced, but the wide range of energy usage between different ages, sizes, and types can significantly affect a program's cost-effectiveness. While it may not always be practical to find precise ages and collect only refrigerators within a particular age range, the determination of defrost type and size are fairly simple. Particularly for programs aimed at replacing old models with new ones, ARCA's testing data provide key information for targeting the guzzlers. Although these results are laboratory tests rather than field measurements, other studies have demonstrated that, on average, the lab tests predict field use accurately. (See How Accurate Are Yellow Labels and What's Wrong with Refrigerator Energy Ratings, HE Jan./Feb. '93, p.30-33.) For further information, contact Bruce J. Wall at ARCA, 300 Plaza Middlesex, Suite 4, Middletown, CT 06457-3470.
--Jeanne Byrne and Alan Meier