EnergyPlus--Quest Competitor or Natural Evolution

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Thanks to all the people who responded to my question.

A few of you ask me to post the result from my very unscientific survey.

The list is split 50%, 50% in their opinion that EnergyPlus will
become a natural transition to eQuest.

The basic sentiment is that eQuest is recognized to be less capable, but
faster and easier to use.

However, almost all who responded recognized that as the demand for
high-performance buildings grows, the ability to accurately predict
energy consumption, C02 emissions, occupant comfort and life cycle costs
are going to become more important. I read this to mean that the
demand for detailed analysis tools like EnergyPuls is likely to

Someone asked me why Bentley cares. We believe that there's a hole in
the U.S. energy analysis/simulation market. We believe, as this survey
indicates, that the tools available to U.S. designers seem to fall into
two camps. Tools that are easy-to-use, but inaccurate/incomplete. Or,
tools that are precise, but difficult to use and slow.

Unfortunately, because of this we see:

1. Many "green" building don't live up to the promises
2. Robust energy simulation is typically reserved for "special"
projects, or certain project types.
3. Accurate energy analysis is typically siloed, as oppose to
integrated into the design process

As the leader in building engineering and analysis software or mission
is "sustaining the worlds infrastructure". As such we're working on
solving this problem,

Dan Monaghan

Dan.Monaghan at's picture
Joined: 2011-09-30
Reputation: 0

Your assessment that EnergyPlus is more powerful than eQuest but much less
inuitive and user-friendly (for those of us used to graphic interfaces)
concurs with my personal observations and what I have heard from my

A U.K based company has developed a proprietary software called
DesignBuilder that embodies EnergyPlus within an eQuest like user-friendly
graphic inteface.

You can download the software for a 30-day free-trial to evaluate its
functionality and capabilities.

Meng Li's picture
Joined: 2011-09-30
Reputation: 0

I work mostly in the existing buildings (non- or pre-"green) markets, but to
the extent green buildings don't live up to the promises is largely due to
operaitons, not design. Many green buildings are more complex, and since
even more traditional buildings typically have significantly sub-optimal
operations, it is only logical that green buildings will suffer at least as
much when compared to expectations/simulation results.

Some interesting documentation of green building performance is available at

As far as Energy Plus and eQuest, I only have experience with DOE-2 and
eQuest. EnergyPlus should be superior since it was built using the best of
DOE-2 and BLAST. IIRC, it was moving away from a transfer-function-based
simulation to a heat balance-based simulation. This should also help it to
be superior in some circumstances. DOE-2 derivative simulation tools are
generally weak at simulating suboptimal operations, and are very poor at
simulating certain controls improvements or retrocommissioning measures. I
don't know how much better EnergyPlus is in this regard.

At any rate, because of federal funding, and that some (many/most?) federal
projects and organizations will only allow EnergyPlus, it seems certain that
EnergyPlus is the future. My use of DOE-2 dates back to before there were
convenient interfaces and we dealt only with BDL and user-defined functions,
and we needed the stacks of documentation to know what we were doing. I
certainly believe that as more interfaces for EnergyPlus are developed, more
students come out of school with knowledge of EnergyPlus, and more of us
learn EnergyPlus, it will see greater and greater use.

William E. Koran, P.E.

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Joined: 2011-09-30
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I agree with your comments about operational issues contributing to lack
of "performance" in high-performance buildings.

However, on the design side, many energy analysis/simulation programs
don't allow for the modeling of sophisticated 'green' heating and
cooling strategies, i.e. mix mode, their plant/system definitions are
limited, and they can't simulate the buildings operation, i.e.
night-time cooling.

The only program EnergyPlus program we've found that overcomes many of
these limitations is Hevacomp out of the UK. For retocommissioning
work, it seems to offer the right set of ease-of-use and capabilities.

Dan Monaghan

Dan.Monaghan at's picture
Joined: 2011-09-30
Reputation: 0

Mr. Koran has made some good points on the power of government funding
to assure that EnergyPlus will eventually overtake DOE2 and eQuest. But
this doesn't guarantee a better simulation code. Doe2 has the backing
of decades of usage and testing by millions of experienced building
simulation modelers worldwide. It has undergone thousands of
corrections and improvements during its lifetime, and has evolved to the
point that it has been widely accepted and used as the benchmark by
which other simulation codes are tested and proven.

So my advice is let's not be hasty in writing off such a powerful legacy
and jumping to something newer just because it is receiving more funding
at this point in time. Wasn't DOE2 conceived and developed under
federal (DOE) funding decades ago? Do we need to start over with a new
baby? We can all point out weaknesses in a tool that we are all
intimately familiar with, but have we spent enough time and effort to
look as carefully and critically at EnergyPlus? Not yet, because we
can't until EnergyPlus (or any other newer software) has undergone as
much usage and scrutiny as DOE2 and its derivitives.

No matter how much money is spent on a newer code, I will personally put
more faith and confidence in the more tried and proven code. That kind
of confidence can't be bought; it can only develop over a long time.
When EnergyPlus has been proven to my satisfaction to be better than
DOE2, then I will be happy to switch.

Remember McIntosh computers and their windows GUI? Has Microsoft
created a better product? I don't think so, but we have been unhappily
forced to switch because most other people have, and it was all due to
money and its power, not a better product. As grass roots users of
DOE2, let's stick together and demand that EnergyPlus be proven to our
satisfaction to be at least as good as DOE2 before we switch. After
all, we pay our government to serve our needs, not to use our money to
dictate our choices.

Glenn Haynes, PE

Glenn Haynes's picture
Joined: 2011-09-30
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I agree with Glenn. I have always regretted the split that occurred
between the eQUEST team and the EnergyPlus team that occurred lo so many
years ago now. We users have paid for that the most. Just think what
tools would be available right now if all those experts were still
working together.....

William cited operations as the reason for green buildings not
performing as they should; Dan thinks it is the tool's fault. I think
we, as energy modelers, better look in the mirror to see who is at
fault. There are a lot of untrained new people entering this field who
think that by possessing an engineering degree, or some other advanced
degree, they should be able to jump right in and do this work. I have
been doing it for 25 years now using a variety of tools and I can tell
you that any tool I use is only as good as my ability to make it work,
and I am still learning how to do that.

It is not correct to assume that the funding for eQUEST is insignificant
just because federal $ are no longer available for it. As far as I know
eQUEST is funded at a level that the current eQUEST team is hard pressed
to spend because there are not enough of them doing the work as well as
not enough hours in the day. Also, they are constantly making changes
and improvement which address the past concerns that people had about
the algorithms, heat balance methodology, etc.

Each team, the EnergyPlus team and the eQUEST team. is composed of
highly educated and trained professionals that are capable of developing
great tools for our use. Each one will eventually function as well as a
user can make it function. And, that again is the biggest problem. The
user, not the tool. We can wish for a model to do this or to do that but
as long as there are users out there, you know who you are, who are
untrained and inexperienced, bad results will be obtained using whatever
tool is used.

Carol Gardner PE

Carol Gardner's picture
Joined: 2011-09-30
Reputation: 0

I agree that there are some serious disconnects occurring between the
design, modeling, construction and building operation. I have been on
projects where the design engineer claimed that all pumps will operate at
variable speeds, but no control valves were specified for coils, meaning
that while pumps are supplied with VSDs, no variable speed pumping is
actually possible. I've also seen projects reported where the design team
touted the installation of high-efficiency boilers (94% or better), and then
also claimed to be saving pumping energy by running loop temperatures hot,
around 180 F. You have to be very careful with this combination. I don't
know of a boiler that can provide 94% efficiency at 180F supply water
temperature without some very fancy heat exchangers.

Sometimes field changes are made that cut into the energy performance of a
building. Simple pipe distribution and pumping changes can have large
energy performance impacts. Simple misplacement of a DP sensor in a pumping
loop can result in inadequate flow to heating and cooling coils. This often
results in an efficient pumping system being forced into an all-on position
so that all systems are provided with adequate flow. Each building tells
its own story. I've seen fantastic engineers produce horrible models
because they understand how buildings work, but not how computer programs

When I first started watching this list-serve, someone said "if you can't
develop a simple excel spreadsheet calculation to estimate what you are
trying to model, you shouldn't be modeling it." I think that we all need to
take this to heart. You should be able to explain each and every result.
If you can't, look through hourly outputs. See how the program is
calculating things. Figure out what is going on. All of the output reports
available from eQuest allow for a window into the calculation mechanism of
the program that is absolutely fantastic. It is unlikely that I will use a
modeling program that doesn't provide me with this sort of transparency, and
post-processing ability.

I have looked through Energy Plus. On the surface it seems that there's
some valuable functionality available that is not currently available in
eQuest, but without a fully-functional graphical user interface, and
extensive testing, none of that matters. Precision does not equal accuracy.


No Username provide's picture
Joined: 2011-09-30
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Karen and Carol,

Attached is a PDF that illustrates you points that knowledge is kingJ

Anyone who deals with MEP systems will enjoy this post.

Dan Monaghan

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Joined: 2011-09-30
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