OpenStudio
Free, open-source EnergyPlus front-end from NREL with a SketchUp plugin, a Measures library for parametric analysis, and Radiance daylighting support.
Vaporware Risk
4.6 /5 composite score
Best free option for a solo architect or engineer who wants full EnergyPlus fidelity -- the SketchUp plugin lowers the geometry barrier and the Measures library adds parametric capabilities at no cost; no commercial support, so budget time for community troubleshooting.
Worth it for a firm of one
Rubric Scorecard
| Criterion | Score | Rationale |
|---|---|---|
| Maturity | 5/5 | DOE/NREL-funded, actively maintained, cross-platform (Win/Mac/Linux); Wikipedia page and decades of academic publication confirm maturity and legitimacy. |
| AEC Specificity | 4/5 | Full EnergyPlus simulation, Radiance daylighting, HVAC systems modeling, parametric Measures scripts, and an SDK for C++/Ruby/C#; ~700 downloads/month. |
| Integration | 4/5 | SketchUp plugin for 3D geometry; OpenStudio Application for HVAC configuration; SDK for scripting; cross-platform; underpins Sefaira and DesignBuilder. |
| Value / Pricing | 5/5 | Completely free and open source; no per-seat cost; the Measures marketplace adds community-built analysis scripts at no charge. |
| Evidence | 5/5 | Wikipedia article; U.S. Department of Energy endorsement; NREL project page; widely cited in peer-reviewed building science literature. |
How we verified this: we checked OpenStudio against its live site and an independent source — en.wikipedia.org. Nothing on this page is listed from memory. See how we review. Verified 2026-06-29.
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