At the recent Bisnow Seattle Sustainability event, energy use intensity, or EUI, was a prominent topic. Tom Paladino called EUI the “BMI for buildings”… and Mark Huppert of the National Historic Trust Preservation Green Lab joked, “Yes, and the city wants to put us on a diet.”
But what exactly is EUI? And why should building owners and operators care?
EUI in Lay Terms
Energy use intensity is simply the energy consumption of a thing, divided by a key descriptive factor of the thing. Miles per gallon (MPG) for cars is a type of energy use intensity.
In the real estate industry typically EUI is expressed by the energy use of the property divided by the area of the property. While a high MPG number means a more efficient car, with buildings you want to see a lower EUI score. That means less energy is being used per square foot.
“Simply” is an understatement because you can quickly disappear down a rabbit hole when defining the numerator and denominator :
- Energy consumption: Whose? The tenant’s, the landlord’s only, the leased car charging stations in the parking garage paid directly by Tesla owners…?
- Square footage: Which? Gross, net, leasable?
Phew! Let’s instead focus on how to use EUI.
What is EUI Good For?
When data is ever more available in reducing cost and complexity, EUI is a useful tool to benchmark performance in large data sets. Benchmarks can be a powerful engagement tool if used appropriately—as soon as our clients know how they perform relative to others, they ALWAYS ask “how do we improve?”
For example, municipalities like New York and Seattle, which mandate reporting of energy consumption from commercial building owners, publish the average EUI results by asset type. These numbers and the citywide scale can engage an entire community around reducing consumption and changing behaviors.
Paladino also uses EUI for large-scale performance improvement projects where it is important to start generating cost savings rapidly, rather than spending years developing the perfect metric.
Currently our team is leading a retro commissioning program at a university campus in Seattle. The industry’s typical retro-commissioning approach starts with walking through each building and gathering building automation system data to identify deficiencies.
Because the buildings on this campus are co-located and therefore the climate is the same at each, this approach lets the data do the work, by categorizing the 28 buildings first by program (lecture, lab, dorm etc.) and then by EUI.
Once it’s determined how far each building is from mean performance on a project, it’s possible to develop packages of energy efficiency measures designed to bring energy consumption back to the target EUI for that group.
Finally, when on site to review building automation system data and retune the buildings, we can clearly address specific systems in specific buildings, which saves the client consultant time and helps capture energy cost savings more quickly.
What is EUI Not Good For?
EUI is not a very helpful metric when area is a not a significant driver of performance, or where the user group can’t define area consistently. For example, in the manufacturing world it makes more sense to benchmark plant performance based on energy use or energy cost per unit of production rather than the size of the manufacturing plant.
This is because the processes, equipment and products produced, along with their associated energy use, can vary widely between buildings.
Paladino is helping ICSC members explore a similar process for retail real estate by using Gross Leasable Area (the unit of production for retail landlords) as a starting denominator in the Property Efficiency Scorecard. As more users enter their data into the Scorecard, more benchmarks are generated based on statistical analysis of a growing data set of performance information that was previously not available to industry.
Analysis of EUI for a retail portfolio
EUI also doesn’t tell you how a specific building is functioning or how to make it perform better. While commissioning a very high performing office with a low EUI, we found a duct heating system was being triggered on every day at 12:15 am while the space was unoccupied, due to an error in the controls system.
This was causing large and unnecessary power draws. The building’s low EUI could have been interpreted as everything is good, but there is always room to improve.
EUI is an informative metric when you want to:
- Categorize large data sets for peer comparison
- Engage user groups with lots of buildings
- Make coarse cuts in the data to get to the end goal faster
- Understand where to begin your detailed analysis
Use a different tool if you need to:
- Definitively categorize building performance
- Identify and resolve building specific issues
When using any benchmarking metric, such as EUI, it’s important to ensure at the start of a project that you are using the correct metrics to give you the data that you need.
Patrick Leonard is Director, PMP®, LEED® AP with Paladino Seattle