twitter youtube facebook linkedin email
Connect with:


Over the past 2 years we have received this question in one form or another from nearly everyone we know, including members of the Department of Energy, architects, engineers, academics, and even some people from inside of Autodesk. It’s a very fair question and we are always happy to answer it. We also thought it would be nice to write a definitive blog post to comprehensively answer the question for everyone.

Adsk E+

Definition of "a better design" = One that reduces total cost of ownership, increases occupancy comfort and significantly reduces the buildings impact on the environment relative to existing design practices.


What does Autodesk believe in with respect to whole building energy analysis?

  • The ultimate goal should be to design buildings that get as close to Net Zero as possible. Code compliance is required and valuable, but we are focused on delivering solutions that produce significantly "better designs" (as defined above). Code compliance will not be sufficient to address those criteria today.
  • Considerations of how to get to Net Zero should start as early as possible in the design process– often before pen even touches paper.
  • Analysis engines should be fast and accurate, but that is not enough—
  • The analysis process should not be about producing a single answer, but rather about providing actionable information to the designer about the behavior of the design and how it can be improved upon without sacrificing aesthetics, comfort, cost, or the environment. This is done by highlighting what factors of the design are most sensitive as well as describing the range of performance for the design.


Why Invest in Energy Plus?

  • We believe EnergyPlus is the most advanced whole building energy analysis engine available in the market. Sure there are other engines that are better at specific things, but when you add it all up, we believe EnergyPlus usually comes out on top overall. 
  • Even though EnergyPlus is very accurate, taking into account the latest in building science and enabling capabilities like green roofs and natural ventilation, it is slow and very hard to use with BIM applications.
  • We thought that Autodesk could address the limitations of EnergyPlus, and do it in such a way to benefit the industry at large. We also did not see anyone else willing to put the effort required to address the limitations of EnergyPlus. We decided if we did not do it, nobody else would and the industry at large would be the worse for it. We have the resources and we know it was the right thing to do.  The classic "If not Autodesk, then who? If not now, then when?"
  • EnergyPlus has one other very important advantage over almost all other modern engines. It is open source. That means anyone can see the source code and improve upon it. EnergyPlus can be used by researchers all over the world to study how to reduce the impact of buildings on the environment without sacrificing cost or occupant comfort. In the long run, open source core technology has shown to be equal to, if not better than, proprietary products. Obviously the core technology must be valuable enough to have a community to rally around it. To support that hypothesis, here are just a few examples: Linux, OSX, Android OS, Mozilla, and the list goes on. All of these have open source as their underlying core technology with customized and sometime proprietary UI on top of them. 


What has Autodesk done to date?

  • We started from day one by collaborating with the DOE to make sure that all the work that we did would be consistent with the DOE standards. We also wanted to make sure that our work would become the new development branch of the EnergyPlus code base, which it now is. 
  • We worked with the DOE managers and developers on a regular basis to get guidance and support. And we must say the experience was a real pleasure. 
  • We converted the EnergyPlus 8.0 Fortran code base to C++. We did this because Autodesk and future developers would not be able to work with Fortran. We also knew from our research that the community of Fortran developers willing to work on EnergyPlus is very small, but if EnergyPlus was converted to a modern language like C++, we could get access to not only a very large community but also leverage both modern programming techniques and development tools. 
  • After the code was converted to C++ we handed every line of code back to the DOE, who started to develop it and released the code base as open source for everyone in the community to see, use, and hopefully improve. 
  • Once the code base was made public, Autodesk took that code base and made the required modifications to have it run on the cloud significantly faster than on the desktop.

E+ Cloud


What is the long term plan?

We are still learning as we go, so the plan is still being formed. However there are a few things we know:

  • Faster: Almost every EnergyPlus model we have seen has been significantly simplified to overcome the performance issues. This produces a model that is so simple it does not take advantage of all the EnergyPlus engine has to offer. We want to increase the performance of EnergyPlus to the point that people do not need to simplify their analytical model. Our interest is to take a model that takes hours on the desktop and run that analysis in just a few minutes in the cloud. We continue to see a lot of opportunities to improve performance.
  • BIM Friendly: Creating an EnergyPlus model is still not simple. Yes, there are tools to help, but nothing is as simple as the frictionless work flow that we have between Revit and Green Building Studio. We want to make it just as simple to run an EnergyPlus analysis from a BIM file as it is to do with GBS

GBS Banner

  • Better Design: At the end of the day, it’s back to designing building as close to Net Zero as possible. By leveraging EnergyPlus and its strengths, we hope to help lead professionals to a better building design that reduces total cost of ownership, improves occupant comfort and significantly reduces the building's impact on the environment. 


How can you help?

  • If you are a student or researcher working on sustainable building related topics, consider using the latest EnergyPlus and contribute to improving the code base and extending its capabilities.
  • If you are a developer interested in sustainability, consider working on EnergyPlus, finding and fixing bugs, improving performance, and making the product more BIM friendly. 
  • If you are an architect or engineer working on buildings and interested in sustainable design, consider using EnergyPlus to analyze your design and tell us what is getting in the way of using it. If you already use EnergyPlus for design or research and your analysis takes close to an hour or longer, use EnergyPlus Cloud for free and see if it makes your work more productive. Also if you find bugs in EnergyPlus tell us about it so the DOE and Autodesk can try to fix it. 
  • If you are a software developer in the sustainability space (regardless of whether you compete with Autodesk or not) consider using EnergyPlus as your core engine. Just remember that the code base is open source and protected, so you cannot take code snippets and integrate them into your code or modifying the code and resell the compiled version of the code as your own engine. 

As a minimum, whoever you are, try to participate in the community in any way you can. Anyone can use the Autodesk EnergyPlus Cloud project as well as the API that we have made available. 

E+ Cloud Project


Tell us what you think

Share your thoughts and provide feedback to help shape the future of energy modeling.

Do you use EnergyPlus? Why or why not?

If you use EnergyPlus for research or in your professional practice, how does EnergyPlus need to develop to become more useful to you?

Have you used EnergyPlus Cloud? What do you think?



Efrat Stark is a Product Manager at Autodesk who works on Autodesk's online properties. Her main products are Autodesk University Online and Community which includes blogs, social share, social sign in, comments, reviews, public profiles, and more.