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Energy Performance Score (EPS) certificate. Image: Energy Trust of Oregon
The need for effective, accurate measurement tools in home energy efficiency has never been greater. Home owners are looking to assess the value and effectiveness of efforts to reduce carbon emissions and save energy. Policy makers and home performance professionals need accurate, graphically instructive tools to evaluate the efficacy of energy efficiency techniques and programs. And it’s increasingly clear that in order to be meaningful and broadly adapted, a measurement system be as accessible to consumers as the miles-per-gallon standard.
On Wednesday, Energy Trust of Oregon released the Energy Performance Score (EPS) Pilot Findings and Recommendations Report, aiming to address many of these demands.
Although EPS is well known among energy efficiency building insiders, it is just now becoming available to the public. Within the overall discussion about moving toward an MPG rating for houses, this report is important, very thorough, and very interesting work.
The Energy Performance Score (EPS) 2008 pilot was born of the need to find an accurate and cost effective way to calculate a home’s energy performance, recognizing that buildings make a substantial contribution to carbon emissions (43%) and energy use, and that changes must be made quickly and effectively. EPS is modeled after the United Kingdom’s Energy Performance Certificate program (EPC), which measures and reports on home energy use and carbon emissions. Energy Performance Certificates are a mandatory element of house sales in the UK. The Certificate is comprised of a score sheet, graphic depictions of energy use and carbon emissions, and a multipage report describing energy improvements that can be made to lower energy use and costs.
We recommend reading the entire Energy Performance Score 2008 Pilot Report for more in-depth discussion of what was undertaken and learned, but based on our review, we wanted to share why we think Energy Trust of Oregon is on to something really important.
1. EPS aims to develop a unified and easily understood means of comparing energy efficiency in houses, whether they are new or existing construction, so that consumers can have a true understanding of what they are buying, the way that we currently understand fuel efficiency in cars. The time has come to put this information into the hands of home buyers, and that cannot be accomplished without first establishing a meaningful basis of comparison.
2. The EPS Pilot Project was rigorous. In order to reach its pilot recommendations, the project looked at 302 houses in Portland and Bend, Oregon. Most of the houses were located in Portland, with a smattering in Bend to insure that cold climate considerations were taken into account.
3. The EPS Pilot scrutinized software tools using meaningful measurements. In order to undertake this study, EPS surveyed over 100 software tools in 190 homes, and honed in on four to determine which was the most accurate, easiest to use during an audit, affordable, and least likely to produce errors. The four that auditors used throughout the study were: REM/Rate, SIMPLE, and two versions of Home Energy Saver (HES). (Of these, EPS settled on SIMPLE as the best overall performer, but noted that the others have the capacity to be tweaked to increase accuracy).
4. The EPS approach assesses both predicted and actual (operational) energy usage. Actual use data from homes was used to evaluate the predictive ability of the software used in the study. The report acknowledges that actual use data were imperfect both because homeowners at times did not report and may have reported inaccurately. Nevertheless, a key recommendation of this report is to make measuring and reporting actual consumption simpler, so that homeowners will feel encouraged to conserve and find creative ways to reduce energy usage. “Measuring consumption directly incentivizes lower home energy consumption, which is the ultimate goal.”
5. The EPS energy score aims to display total energy usage to homeowners in a graphic and readily understood format. In their own words:
The EPS energy score should be expressed as the total annual energy required for the house under normal conditions and be expressed in kilowatt hours per year. This score should be illustrated on a scale that also indicates the energy use of different fuels, relevant local comparisons, energy upgrades for existing homes and built to code comparisons for new homes, and community energy goals.
Two aspects of this recommendation are key: the first is the determination to consider the house in its entirety, the second is that the presentation of data must be visually comprehensible. As we have learned in our own monitoring project, graphic representation of data is extremely helpful.
6. The EPS approach calculates carbon emissions, in order to present a full picture of home energy use. The EPS takes into account different fuels (rather than just electricity use or oil, for example), and provides a carbon score that “balances the fuel efficiency bias that would result from only using an energy score.”
7. Finally, and perhaps most importantly, the EPS report takes into account what homeowners actually want. In their words:
Reporting Results, Surveys, the United Kingdom’s EPC progress, and anecdotal information from the field technicians all indicated that homeowners want to gain information about how to improve the energy performance of their homes. Ideally, they would like to know the cost of these upgrades and the anticipated savings. Given that the accuracy of the modeling tools was not known until the end of the pilot, the EPS team developed an Interim EPS Report that generally outlined the energy performance of a home and recommendations for improvements. This report was provided to the homeowner.
