All energy end-uses are simulated based on standard energy engineering and thermodynamics principles. Heating and cooling energy use is simulated using the DOE 2.1E calculation engine, and all other end uses are simulated using algorithms and data developed at LBNL. Logic for determining default values, etc., were developed at LBNL.

HES as a website can be served from any webserver to any web browser. The interactive portion was built on and for an Apple Macintosh, but can also run on IBM PC or any UNIX machine. The underlying database could be any ODBC-compliant database, but after years of working with a MAC-platform DBMS, in January 2000 we moved to an ORACLE datebase managment system. The DOE-2 calculation engine runs on an IBM PC but could run on a UNIX machine. The SEND.CGI that handles IO for DOE-2 can only run on Windows NT/IBM PC. The site runs on the Apple MacOS 8.5.1, except for DOE-2 and SEND.CGI which use a Windows NT Server, all "off the shelf."

The programming languages used were:

• Web pages–HTML & JavaScript.
• Interactive forms–Tango & SQL.
• CGI–Visual Basic.

This is the most well-validated and well-documented residential energy calculation framework. It provides the most extensive decision-support features of any comparable tool. HES is available internationally via the Internet, without the need for traditional software distribution/installation. Requires Internet access and a forms- and frames-enabled web browser.

Related and Auxiliary Software used during or in support of construction includes:

• DOE 2.1E (developed at LBNL).
• Pervasive’s Tango Editor developed the interactive forms.
• StarNine’s WebStar web server.
• ORACLE is the database managment system.
• Adobe PhotoShop,
• BBEdit, and MS Excel were also used.

User sessions require less than 1 minute for simplest user level; up to 60 minutes for advanced/detailed user level.