Refrigerator Power Efficiency

It has been claimed that new refrigerators use much less power than old ones. This is also the premise of The Great Refrigerator Roundup program that encourages replacement of refrigerators older than 15 years. Here is one comparison, measured over about 3 days.

New Old
Year 2010 1992
Capacity (ft3) 18.1 ~15
Duty Cycle (%) 25 43
Average On Power (W)
(Includes compressor and defrost)
101 155
Average Power (W) 25 67
Average Power (kWh/yr) 221 585
EnerGuide Rated Power (kWh/yr) 335 816

The new refrigerator uses 38% of the electricity of the old one, while also being 20% bigger. Assuming $0.10/kWh, the new refrigerator saves $36.40/year. Both refrigerators use about 70% of their rated consumption.

Update: 2017 July (6.7 years later)

The refrigerator now uses about 40% more power than when it was new. Unfortunately, I don’t know why the efficiency changed, and I don’t have any intermediate data points to show when the efficiency started to get worse.

New At 6.7 years
Year 2010 2017
Duty Cycle (%) 25 35
Average On Power (W)
(Includes compressor and defrost)
101 100
Average Power (W) 25 35
Average Power (kWh/yr) 221 306
EnerGuide Rated Power (kWh/yr) 335

I believe the lower efficiency is not due to the following causes:

  • Dust accumulation: I thoroughly cleaned the dust off the condenser and saw no change in power consumption. (I measured for 300 hours before and 1500 hours after cleaning.)
  • Ambient temperature: The indoor temperature varies by a few degrees between winter and summer, where summer temperatures can cause the refrigerator to do more work. I saw a change in power usage of about 7+/-2% between April and July 2017, so the indoor temperature change between seasons can only explain a small part of the 40% change.

Interestingly, all of the efficiency loss is due to an increased duty cycle. The on-power hasn’t changed.

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