Energy impacts of defrosting in household refrigerators: Lessons from field and laboratory measurements

Many modern household refrigerating appliances have automatic defrost systems that keep the evaporator clear of frost and ice and obviate any user interaction to remove frost accumulation that occurs during normal use. The energy impact of defrosting has received little attention to date and there is little understanding on how these systems operate in homes. This paper uses laboratory measurements for 110 appliances over a period of weeks and field measurements for 195 appliances over periods of up to one year to observe the energy characteristics of defrosting systems. Field data covering some 55,000 individual defrost events has been analysed to obtain unprecedented insights into defrosting intervals during normal use. This data also provides useful information about the pattern of defrosting and a comparison between laboratory measurements and field measurements. A method to estimate incremental defrost and recovery energy in normal use is proposed.