The Net Impact of Home Energy Feedback Devices

March 01, 2010
March/April 2010
A version of this article appears in the March/April 2010 issue of Home Energy Magazine.
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Recently, much attention has been focused on modifying the way individuals interact with energy consuming products in their homes. In order to examine the viability of real-time feedback devices to produce energy savings, Energy Trust of Oregon, piloted a study using the Blueline PowerCost Monitor. Energy Trust manages Oregon’s portion of the public purpose charge for investor-owned electric and gas utilities. The agency manages energy efficiency and renewable energy programs that span residential, commercial, and industrial sectors. Currently, the residential program focuses on retrofit and incremental energy conservation measures, solar energy systems, and also offers free home audits, called Home Energy Reviews (HER). This article details the net impact of the monitor on electricity use for “early adopters” and HER participants.

Enter the Monitor

Energy Trust began investigating potential products for a home energy monitor (HEM) pilot because of an interest in findings from Canadian utility pilots of instantaneous feedback devices. The agency chose the Blueline PowerCost Monitor because homeowners could install the device themselves. Following product testing, Energy Trust launched a small-scale pilot in January 2008 with installations continuing through August 2008. The pilot tested two delivery mechanisms: self installations by the customer (early adopters), and Home Energy Review (HER) installations. In the first method, the monitor was offered for purchase through Energy Trust’s Web site for a discounted price of $29.99; the typical retail price at the time was $150. A total of 164 monitors were sold through the Web site. In the second delivery mechanism, the monitors were offered to customers during HERs and were installed by the auditor at no cost. In total, the pilot consisted of 164 “early adopter” households and 201 HER households. Pilot households we also surveyed twice, once shortly after the monitor was installed and again at six months after installation, to gather information about use of the monitor.

Surprising Findings

For the early adopters, the estimated savings from an HEM were not significantly different from zero. Despite a large majority of participants reporting a reduction in energy use attributable to the monitor during the study period, post-period reduction in electricity use was statistically identical for the participant and comparison groups. This is not the intuitive result we expected, given that these participants were eager, self-selected adopters who had to pay a non-trivial amount of money for their HEMs. If any group should show above average reductions in consumption, this would be the group. HER installed monitors also had no significant effect on household energy consumption.

Significant attrition occurred by the end of six months, with response rates of 57% and 55% for self-installed and HER-installed monitor participants, respectively. The six month surveys gathered a number of key data points about monitor longevity and household use of the monitor. Regression billing estimates of monitor impact on energy consumption took into account all participants, as well as the subset of survey respondents.

For both groups, point estimates of energy savings, while never significant, were highest within three months of installation, and declined as the post period was extended to six or nine months. This finding seems to indicate that participants may have been taking steps to reduce consumption shortly after installation, which diminished over time. The failure of some units due to a manufacturing defect may have contributed to this attenuation of energy savings.

Other Findings

Several confounding factors were also at play during the study period. Participants and their comparison groups saw electric rate increases as well as a declining economy, likely resulting in an overall decrease in energy consumption. Participants may have felt that the monitor was aiding them in reducing their consumption while in reality economic trends were resulting in widespread reductions in energy usage among all utility customers.

It does not appear that instantaneous feedback devices can be counted on to deliver large savings. While a decline in savings stemming from these devices could be expected over time, results of this study indicate that the monitors have no appreciable immediate impact. Given the level of interest in this technology, and the volume of program pilots currently in the field nationwide, impact results from much larger studies using a variety of delivery methods, with the possibility of analyzing subsets of participants, should help inform the applicability of instantaneous feedback devices in the residential market.

Brien Sipe does evaluation research and project management with Energy Trust of Oregon. Projects include estimating impacts of residential weatherization retrofits through billing analysis, and examining long run trends in program participant energy consumption. 

Sarah Castor conducts program evaluation research as a Project Manager with Energy Trust of Oregon.  Current pursuits include behavioral market research in the residential sector.

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