SystemSimulator, the free online building thermodynamic simulator
Model any building or campus, and analyze energy usage with real-world weather data
Model any building
Worldwide weather data
Include renewables
Desktop monitor background
Quickly build any structure
SystemSimulator is powerful enough for auditors to use, yet simple enough for enthusiasts to run. We also welcome engineers and developers to use BuildingSim to develop new and improved Halo/S™ algorithms to help reduce the world's energy usage.

Create any building — from a one-room apartment, up to a 100+-floor skyscraper — and account for everything from window coverings to shade trees. Using actual hourly weather data from over 90 climates around the world, this software numerically solves full thermodynamic differential equations every minute of the year, giving you the actual energy usage down to the cent. BuildingSim can be used to accurately simulate the effects of both construction and thermostat control algorithms.
Chart and optimize
Every simulator parameter is available to chart, allowing an unprecedented view into where energy is going inside a building.
Comprehensive feature list
  • Calculate the energy savings from home improvements
  • Analyze the energy cost trends from different climates or building types around the world
  • Measure accurate energy savings by using new thermostat control programs
  • View the seasonal changes of energy usage to plan ahead