The U.S. Department of Energy has released the results of a study exploring the energy-reporting accuracy of market-available connected devices.
Advanced building systems such as connected lighting increasingly have greater functionality and energy-dependent operating modes. This increased functionality makes energy consumption estimates more complex because energy performance is dependent on what operating modes are used and how much time is spent in each mode. Devices and systems that can report their own energy consumption mitigate this uncertainty.
The study, conducted by Pacific Northwest National Laboratory at its Connected Lighting Test Bed, was intended to generate awareness of building systems capable of reporting their own energy consumption and further interest in the value of energy data for a variety of uses. The results draw attention to how the accuracy of reported metrics can be characterized and quantify the performance variation found in market-available products.
The study considered two residential-market products and three commercial-market products with the ability to report the power drawn and/or energy consumed by devices connected to their electrical outlets. Energy consumption data reported by the devices was compared to measurements taken by a reference meter under 10 test conditions. The residential products reported power draw but not cumulative energy consumption; the commercial products reported both power draw and cumulative energy consumption.
Analysis of the results revealed variations across devices and test conditions, as summarized in the figures below.
The average relative reporting error (RRE) of the two residential products, derived from the reported power draw, was −0.02% and −1.20%. The average RRE for two of the three commercial products, derived from reported power draw, was greater than those of the residential products (−2.40%, −2.72%, −0.36%). The average commercial-product RRE derived from reported energy consumption should be very consistent and better than performance based on reported power draw. However, the RREs derived from reported energy consumption varied significantly (17%, −10.78%, −1.5%) across the three makes of commercial-market products and was uniformly less accurate than performance based on reported power draw. Subsequent analysis identified a number of root causes for this decrease in performance, most of which were related to reporting resolution.
The results of this study and subsequent related work may be relevant to stakeholders in industry specification and standards development organizations. The methods this study employs could inform test and measurement procedures and performance classifications for connected outlets, lighting products, and other building systems capable of reporting their own energy consumption. The report concludes with technical recommendations for manufacturers, the standards and specification community, and system designers and specifiers.
Check out the report here.
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