Software to Analyze Home Energy Performance

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Analyzing your passive solar home's energy performance by hand is long-winded, cumbersome, and prone to error. Between ten and twenty years ago, a variety of software tools appeared on the market, ranging from DOS-based utilities to basic Windows apps.

Over time, most of these programs have disappeared. Some were discontinued because they weren't popular enough, some vanished because they were based on obsolete operating systems, and others were simply discontinued through lack of support.

These days, there are many energy modeling programs available, but the one which is the most popular (probably because it's free) is the US Department of Energy's EnergyPlus. The program has been around since 2001 and is updated regularly (2013 saw the release of version 8).

EnergyPlus comes with full documentation, explanations of calculations, and a variety of other useful information. It also has a bunch of add-ons to connect it to other programs, a web tool to pull in weather data, and open source projects to do things like redefine the user interface.

EnergyPlus models heating, cooling, lighting, ventilation, other energy flows, and water use. It includes time-steps less than an hour, modular systems and plant integrated with heat balance-based zone simulation, multizone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems.

You will have to create an account on the DOE's website to download the software.