A Scalable Non-intrusive Load Monitoring System for Fridge-Freezer Energy Efficiency Estimation

In this paper we propose an approach by which the energy efficiency of individual appliances can be estimated from an aggregate load. To date, energy disaggregation research has presented results for small data sets of 7 households or less, and as a result the generality of results are often unknown. In contrast, we have deployed household electricity sensors to 117 households and evaluated the accuracy by which our approach can identify the energy efficiency of refrigerators and freezers from an aggregate load. Crucially, our approach does not require training data to be collected by sub-metering individual appliances, nor does it assume any knowledge of the appliances present in the household. Instead, our approach uses prior models of general appliance types that are used to first identify which households contain either a combined fridge-freezer or separate refrigerator and freezer, and subsequently to estimate the energy efficiency of such appliances. Finally, we calculate the time until the energy savings of replacing such appliances have offset the cost of the replacement appliance, which we show can be as low as 2.5 years.