EnergyPlus
Free, DOE-funded whole-building energy simulation engine with sub-hourly HVAC, lighting, and water modeling -- the engine under most commercial tools on this list.
4.0 /5 composite score
C1 5/5 reflects the free license, C2 4/5 reflects CLI plus the Python and C APIs, and C4 5/5 reflects IDF, epJSON, gbXML, CSV, SQL, ESO, and ERR workflows. Integrations include OpenStudio, DesignBuilder, Ladybug/Honeybee, ClimateStudio, IES VE, eQUEST, and Simergy; firm-size fit is solo to small-team.
Worth it
Rubric Scorecard
| Criterion | Score | Evidence |
|---|---|---|
| Value for the price | 5/5 | Free, free tier Source → |
| Agent Friendliness | 4/5 | CLI, API: https://energyplus.readthedocs.io/en/latest/api.html (Python API + C API) |
| Ease of adoption | 2/5 | -- |
| Portability & lock-in | 5/5 | 7 file formats |
| Interoperability | 4/5 | 8 integrations |
Pricing
ModelFree
Free tieryes
How we verified this: we checked EnergyPlus against its live site and an independent source — energy.gov. Nothing on this page is listed from memory. See how we grade. Verified 2026-06-30.
Evidence
File formats
| Format | Direction | Support |
|---|---|---|
| IDF | unknown | unknown |
| epJSON | unknown | unknown |
| gbXML | unknown | unknown |
| CSV | unknown | unknown |
| SQL | unknown | unknown |
| ESO | unknown | unknown |
| ERR | unknown | unknown |
Integrations
OpenStudio DesignBuilder EnergyPlus Measures Ladybug/Honeybee ClimateStudio IES VE (Apache) eQUEST Simergy
Sources
Alternatives in Energy Analysis
Free, open-source EnergyPlus front-end from NREL with a SketchUp plugin, a Measures library for parametric analysis, and Radiance daylighting support.
4.4/5
SaaS whole-life-carbon data platform used by architecture and engineering firms to run rapid embodied, operational, refrigerant, and landscape carbon (LCA) assessments from concept through construction, benchmark portfolios, source low-carbon products via EPDs, and auto-generate AIA 2030 DDx compliance reports. Grew out of EHDD's in-house carbon tool (EPIC) and is separately licensed to power Autodesk Forma's Embodied Carbon Analysis feature.
4.4/5
Free open-source Grasshopper plugins for climate analysis, energy modeling, daylighting, CFD, and urban simulation, with a commercial cloud layer via Pollination.
4.0/5
Cloud-connected building-performance and environmental-simulation platform from Ladybug Tools LLC, delivered as Rhino/Grasshopper and Revit plug-ins that build and run EnergyPlus, Radiance, and OpenStudio models from CAD/BIM geometry for daylighting, energy, and CFD analysis.
4.0/5
See all EnergyPlus alternatives → ยท Compare all Energy Analysis tools →
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