HVAC Load Calculations Made Easy
Get fast, precise load calculations with HeatWise, our online HVAC load calculator. Made for mechanical engineering firms and consultants.
No credit card required.

Get fast, precise load calculations with HeatWise, our online HVAC load calculator. Made for mechanical engineering firms and consultants.
No credit card required.
HeatWise is designed to improve on similar software like HAP and CHVAC. We have all the features you'd expect, with additional tools to make your life easier.
Use our web-app to calculate detailed load breakdowns for your residential and commercial building projects. Load breakdowns give a detailed picture of where the heating and cooling loads are coming from.
Our calculations are based on the 2021 ASHRAE Fundamentals Handbook, using the Radiant Time Series calculation method. We calculate system cooling loads for each hour of one day of each month, for a total of 12x24 samples. We then find the peak loads and show a breakdown by component.
We support entering the following components for each space: ventilation, infiltration, walls, windows, doors, roofs, skylights, shadings, floors, partitions, buffer spaces, people, lighting, motors, appliances, and more. We have intuitive input forms for each one, and provide detailed load breakdowns by component.
We use your location data to calculate the precise solar irradiance entering your building through windows and skylights. See detailed charts of solar irradiance throughout the day, and tweak your windows for maximum efficiency. We also support external and internal shadings, which may operate on a user-defined schedule.
HeatWise is designed to be easy to use and learn, with a modern user interface. Many inputs, like ventilation, have an "automatic" mode where we can calculate the values for you based on your building's specifications. This saves you time digging through reference manuals and ASHRAE standards.
Our integrated Quick Help system guides you through the input process. It provides in-app help for every page of the app so that you are never left guessing. Calculate loads start to finish without time-consuming and expensive training courses. We also provide detailed explanations of what calculations are being performed so that you can sanity-check results.
Load ASHRAE weather-station data for locations across the world. Adjust any location data values to suit your needs. We use this data in our calculations to precisely estimate your building's outdoor temperatures and solar irradiance values throughout the year.
Our software runs right in your browser, on any platform (Windows, Mac, Linux). This means no software to install, no updates to worry about, and no compatibility issues. Share your projects with co-workers across any device and platform.
HeatWise is increasingly being used by firms and consultants looking for a modern load calculator. Here are a few testimonials from our users:
" When our IT department restricted downloads of our outdated, unsupported load calculation software, HeatWise provided the perfect solution - its web-based platform eliminated approval bottlenecks and deployment hurdles while delivering straightforward, accurate calculations for our needs in an industry that has become unnecessarily complicated with new energy modeling platforms and different calculation methods. "
Using HeatWise to assist with commercial building load calculations.
" I used HeatWise to calculate heating/cooling loads for a fourplex project. I'm stunned by the user-friendliness, interface, and the graphics provided at the end of the calculation. I'll use HeatWise for my projects going forward and recommend it to HVAC engineers! "
Used HeatWise to calculate loads for an energy-efficient fourplex residential project.
" The software is very easy to use. The interface is friendly and clear. "
Tried HeatWise for a commercial project. Was able to get calculate loads without HeatWise training.
Let us take the headache out of load calculations for you. We designed HeatWise to be easy to learn and use so that you can get results fast.