The Home Energy Saver quickly computes a home's energy use on-line, based on methods developed by Center researchers. By changing one or more features of the modeled home to improve energy-efficiency, users can estimate how much energy and money they can save. Users benefit from a constantly evolving information base that is more timely than resources published in static electronic media. Hypertext links lead the user to hundreds of other Web sites that provide detailed information on energy-efficient products, home builders, residential utility programs, government programs, practical newsletters, energy software, and other useful topics.

The Site's Four Elements
The Home Energy Saver Web site consists of four main elements. With a single mouse click, the Quicklook module instantly compares energy use for typical and energy-efficient homes in different parts of the country. The Home Energy Saver's Virtual Home Energy Advisor goes a step further by calculating energy use in a particular city, based on a detailed description of the home provided by the user. In addition to calculating energy use on-line, the Home Energy Saver's Librarian connects users to an expanding array of related information resources on the Internet; the Answer Desk provides answers to a variety of frequently asked questions.

The Virtual Home Energy Advisor uses the DOE-2 building simulation program to estimate heating and cooling energy consumption. DOE-2 performs a very sophisticated series of calculations, but the user interface is relatively simple. A full annual simulation for a typical weather year (involving 8760 hourly calculations) takes about 10 to 20 seconds, once the user has entered information describing the home. Users can choose from more than 250 weather locations around the United States. Default energy prices for each fuel and state are available, or users can enter a specific price.

The Virtual Home Energy Advisor also calculates domestic water-heating energy consumption, using a model developed by Center researchers. Users can see how the number and age of occupants, equipment efficiencies, and water-heater thermostat settings affect bottom-line energy costs. And by entering the number and approximate age of their major domestic appliances, users can estimate the appliance's energy consumption, based on historic sales-weighted efficiency data. Two very detailed modules estimate energy consumption for lighting and dozens of miscellaneous gas and electric appliances, and lighting, using default values based on data collected over the years by Center researchers.

Advantages of Web-Based Tools
A Web-based approach has several distinct advantages over the traditional software production and distribution process. First, given the sophistication of Web development tools, the user interface can be designed (and subsequently modified) with considerably less effort--and thus lower cost--than with traditional methods. Second, the cost to distribute the product is minimal. Furthermore, future refinements or additions to the program do not require physical redistribution or reinstallation of the software or documentation; changes need only be made to the master version (located on the home server) for all users to have the benefit of those changes. Any user with a forms-enabled Web browser, regardless of platform, sees a seamless interface free of most hardware and software compatibility and installation problems. Regardless of the computing resources they have available, users have access to powerful computational engines residing on the host server. Lastly, the Web provides immediate access to all the other relevant energy-efficiency information that is constantly evolving on the Web.

The first phase of Home Energy Saver development is now complete. The next phase will focus on further developing the site into a one-stop shop for homeowners seeking to improve energy efficiency. The site will suggest the most cost-effective changes to make to the house, link to information about products available for these upgrades, and offer information on selecting a contractor and participating in utility programs.

--Evan Mills

Evan Mills
Center for Building Science

Visit the Home Energy Saver.

This work is sponsored by the U.S. Environmental Protection Agency, Atmospheric Pollution Prevention Division.