Home Energy Saver

The Home Energy Saver project was launched in 1994 as the first web-based energy audit and carbon-footprinting tool, and one of the earliest websites at LBNL. It delivered detailed estimates of a home's energy use and carbon emissions (by fuel and end-use) and a tailored list of applicable energy efficiency improvements, ranked by payback time. The site first went online in 1996, just as the World Wide Web was expanding from an academic to a significant public presence. The underlying engine was the DOE-2 hourly simulation engine, which was previously accessible only by a specialized community of energy engineering experts with powerful computers, now bundled with other models and data developed by publicly funded R&D institutions .... making sophisticated resources available to the general public in a highly usable and customizable home energy self-assessment. As a cloud-based tool, it could be run on any internet-connected computer irrespective of operating system or capacity; no local software was required. Derivative versions were developed for home energy professionals and for multifamily buildings under the DOE Weatherization Assistance Program. Available in parallel with the analysis tool was a substantial body of decision-support information regarding efficient appliances and equipment, financial incentives, user stories, helpful government initiatives, etc., developed in partnership with Home Energy magazine based on their articles as well as their No-Regrets Remodeling book. The site had millions of visits. Approximately 80% of users were homeowners or renters, with the balance made up of those who visit for professional/educational reasons, such as building professionals, educators, contractors, etc.

The project was led by Evan Mills and the final core team included Leo Rainer and Norm Bourassa. Many others at LBNL contributed over the years, including, in alphabetical order: Celina Atkinson, Peter Biermayer, Chris Bolduc, Jordan Brinkman, Rich Brown, Kerey Carter, Allan Chen, Jesse Cohen, Katie Coughlin, Teresa Forowicz, Gregory Homan, Joe Huang, Sondra Jarvis, Clay Johnson, Steve Konopacki, Jon Koomey, Jim Lutz, Nance Matson, Robin Mitchell, Mithra Moezzi, Bruce Nordman, Erik Page, Maggie Pinckard, Brian Pon, Hongjie Qu, Marla Sanchez, Z Smith, Gabor Torok, Sam Webster, Iain Walker, Jeff Warner, and Richard White. Bighead Technologies provided software and infrastructure engineering. Usability consultants Kath Straub and Dianne Chojnowski made major contributions to the interface design and led our associated social network strategy.

The initial sponsor of HES was the U.S. Environmental Protection Agency's Energy Star program.  The U.S. Department of Energy subsequently became the prime sponsor. Other supporting institutions included Touchstone Energy and the National Association of Rural Electric Cooperatives, The U.S. Department of Housing and Urban Development, and the California Energy Commission, and Infosys.

We produced highly detailed technical documentation of the analysis logic, calculation methods, assumptions, and underlying data, along with a series of technical publications and presentations.

When comparing with measured energy use from well-characterized homes, we found that the site was accurate, on average, to within 1% of actual energy use, with the majority of individual estimates within +/-25% of actual. Here's that paper.

The Home Energy Saver was referenced in hundreds of news articles and other outlets, including the New York Times, Washington Post, and USA Today, as well as consumer-oriented sources such as Oprah's O magazine, Martha Stewart Living, and Better Homes & Gardens, plus a Wikipedia page. A resource called Energized Learning used HES to provide a "virtual lab"for high school teachers and their students. Hundreds of utilities linked to the tool to make it available to their customers. The site had ~70,000 followers on Twitter. The integrated Home Energy Pros network had 6,000 members including home performance contractors and other practitioners. APIs were created to help third-party software developers leverage the analytics.

Application programming interfaces ("APIs") enable private and public software developers to tap a remote tool or data feed within a user interface of their own design. The HES APIs were employed by about a dozen licensees to create derivative tools using the HES engine and data, with user experiences designed for specific audiences and use cases.  Microsoft was the most prominent licensee, with the system underpinning their Hohm tool.

Federal Laboratory Consortium Award see also FLC site (2022), R&D 100: One of the best 100 inventions of 2009 (2010), Energy 100: One of the best 100 innovations during DOE's 23-year history (2000), PC Magazine: One of the Top 100 Undiscovered Websites (2004)

Many derivative LBNL tools have been based on the Home Energy Saver, in addition to those developed using our APIs. In 2000, the Energy Star program sponsored the development of a simplified consumer web site derived from the HES, called Home Energy Advisor, which employed a more constrained building description and provided different outputs. A tool for assessing multifamily buildings (MulTEA) was later developed in partnership with the Oak Ridge National Laboratory. The Home Energy Saver was also used to create the Home Energy Score tool, which remains in wide use around the country to produce "miles-per-gallon" type ratings for single-family homes. As of November 2024, over 258,000 homes had been scored.

Public funding to develop and maintain the site was sunsetted, and as of 2023 the site is no longer online. 

• Mills, E., N.J. Bourassa, L.I. Rainer, G. Homan, N. Merket, D. Parker, G. Dickey, and J. Glickman. 2014. “Asset Rating with the Home Energy Scoring Tool," Energy and Buildings 80:441-450 [PDF]
• Parker, D., E. Mills, L. I.Rainer, N.J. Bourassa, and G. Homan. 2012. "Accuracy of the Home Energy Saver Energy Calculation Methodology," Proceedings of the 2012 ACEEE Summer Study on Energy Efficiency in Buildings, American Council for an Energy-Efficient Economy: Washington, D.C. [PDF]
• Chojnowski, D., K. Straub, E. Mills, and T. White. 2012. "Online Communities for Creating Change: Home Energy Pros," Proceedings of the 2012 ACEEE Summer Study on Energy Efficiency in Buildings, American Council for an Energy-Efficient Economy: Washington, D.C. [PDF]
• Mills, E. et al. 2007. "Home Energy Saver: Documentation of Calculation Methodology, Input Data, and Infrastructure." LBNL-51938 [PDF] - online version
• Mills, E. 1997. "The Home Energy Saver: Interactive Energy Information and Calculations on the Web." Center for Building Science News 16(4):1-2. LBL/PUB-731.

• Residential Energy Modeling with The Home Energy Saver [PDF]
• Accuracy of the Home Energy Saver Energy Calculation Methodology - 2012 ACEEE Summer Study on Energy Efficiency in Buildings, Asilomar, CA [PDF]
• Web Services that Foster Innovation in Buildings Energy Analysis Tools - 2012 ACEEE Summer Study on Energy Efficiency in Buildings, Asilomar, CA [PDF]
• Online Communities for Creating Change: Home Energy Pros [Poster] - 2012 ACEEE Summer Study on Energy Efficiency in Buildings, Asilomar, CA
• The Home Energy Scoring Tool: A Simplified Asset Rating for Single Family Home - 2012 ACEEE Summer Study on Energy Efficiency in Buildings, Asilomar, CA [PDF]
• The Home Energy Saver Do-it-Yourself Survey - Touchstone Energy Cooperatives / National Rural Energy Cooperative Association meeting, San Antonio, TX, May 16, 2006 [PDF]