Commercial Building Energy Usage

All commercial buildings in the U.S. together consume 6,787 trillion btu of energy per year, spending $141.238 billion.

Generating heat (for space heating, water heating, and cooking) is overwhelmingly done with natural gas, and electricity overwhelmingly powers other tasks. Natural gas is better suited to heating than electricity because natural gas converts directly to heat when burned. Electricity is better suited to everything else because it’s a very precise and controllable (“high-grade”) form of energy.

High-grade energy is relatively expensive. While electricity accounts for 60.13% of energy consumption (on a Btu basis), it accounts for 84.25% of energy expenditures. It makes sense that electricity is more expensive than natural gas, considering that natural gas is (on average) a major input to producing electricity and there are losses in that process.

There are 96.423 billion square feet of commercial building floorspace in the US, across 5,918,000 buildings. That works out to a median annual energy consumption of 45,000 Btu per square foot (an amount of energy equivalent to 37% of a gallon of gasoline) and an expenditure of $1.46 per square foot.

The energy intensity (energy consumed per square foot) of a building depends on its purpose. Most building purposes have similar energy intensities, reflecting lighting and HVAC load. Buildings with higher energy intensities have a higher density of “other stuff” - refrigerators, cooking, equipment, etc.

We can confirm this by looking at how much each end use contributes to the fuel intensity of each building type. Cooking, refrigeration, computing, and miscellaneous plug loads set the highly energy intensive building activities apart. (There’s also a surprising amount of difference in HVAC intensity between building types. Inpatient hospitals use 105,000 Btu while hotels use 34,600 Btu per square foot.)

Of course, building types differ significantly in their number and square footage. Here’s the aggregate energy consumption of the different building types. Education, one of the least energy intensive building types, is one of the largest energy consumers because there are so many buildings of this type and they are very large.

This next graph shows the effect that building count and floorspace has on energy usage. Building types to the right of the line have disproportionately high square footage per establishment, and building types to the left have low square footage per establishment.

Inpatient hospitals stand out for having a very high square footage per establishment (second only to Enclosed Malls) and also a high electricity intensity due to unusually high plug load. These factors combine to make Inpatient hospitals the highest energy consumers per establishment by far (4.8 MMBtu versus 3.5 MMBtu for Enclosed Malls).

Instead of looking at consumption of all energies (in TBtu), let’s start to focus on spending on electricity (in $). This next graph teases apart the impact of floorspace on electricity spending.

Building types to the right of the line have disproportionately high aggregate spending for their aggregate square footage. Unsurprisingly, these building types have high spending intensity.

The 5 most electricity-intensive building activities are, in order: Fast Food, Grocery Store, Convenience Store, Restaurant, and Refrigerated Warehouse. All but the last one are Food Service / Food Sales. That’s no surprise. We see below that the electricity intensity of Food Service and Food Sales is mostly due to cooking and refrigeration loads.

The “Other” category’s electricity intensity includes significant computing load, which leads me to believe that light data centers are included in this survey under “Other”. The other building activities with significant computing load are Inpatient and Outpatient health care establishments and Office buildings, three building types that frequently have on-premises computing.

As is tradition on this blog, let’s now do a big 3D scatterplot.

A few takeaways:

• Very high spending per building for Enclosed Malls ($712k), Inpatient hospitals ($621k), Refrigerated Warehouses ($356k), and Laboratories ($211k) due to buildings of these types having both high electricity use per square foot and high square footage per building.
• Other building types have very similar spending per establishment because although they vary in square footage per establishment, they have a similar electricity intensity per square foot.
• Building types with the highest aggregate spending are Admin./Pro. Office ($13.1B), Strip Shopping Center ($9.0B), Retail Store ($5.8B), Inpatient hospital ($5.6B), and Mixed-use Office ($5.2B) due to high total floorspace.

Now that we have our heads around where electricity consumption is coming from and going towards, let’s figure out who’s paying the bill. That’s important because owner-occupied structures have a greater incentive to make energy efficiency investments, and government-owned structures may have special requirements to do so.

Education and public order establishment floorspace is overwhelmingly government-owned. Religious and Inpatient establishment floorspace is overwhelmingly owner-occupied. The other establishment types are a mix of owner- and tenant-occupied, with warehouse, office, and mercantile floorspace having a higher proportion of tenant-occupied floorspace.

Although Mercantile establishments are among the highest aggregate spenders on electricity, their low proportion of owner-occupied floorspace would seem to make them a relatively poor candidate for energy efficiency investments. Warehouse spaces have the most owner-occupied square footage, but their low electricity intensity makes them middling consumers in aggregate. The high proportion of owner-occupied Inpatient floorspace makes that establishment type a great candidate considering its overall high consumption.

It’s not worth visualizing, but the survey data indicates that in government and owner-occupied structures, the owner is almost always responsible for managing the structure’s energy systems. For tenant-occupied structures, 53% of floorspace has its energy system managed by the owner.

Finally, let’s look at how many buildings have on-site generation.

Unsurprisingly, the most safety-critical building types - public order (e.g. police and fire stations) and inpatient hospitals - are most likely to have backup diesel generation.

Building types with a high proportion of diesel backup aren’t much more likely to have a higher proportion of solar. That’s because the two on-site generation technologies achieve different goals. Diesel generation is used as a backup when grid power goes out, whereas solar panels are used to lower the cost and carbon emissions of the building’s electricity use.

When this survey was taken in 2018, only 1.6% of all buildings had solar panels, and the only building types with solar panels were Public Assembly (3.3%), Education (3.2%), Mercantile (1.9%), and Office (1.8%). Warehouses, which have lots of roof space, had no solar panels in the survey. This shows how rapid the buildout of rooftop solar has been, as a cursory look at Google Maps shows many distribution facilities in my area with solar panels today.

But ownership type predicts solar penetration better than building type in this survey. While 1.2% of all non-governmental buildings had solar panels and 0% of state or local buildings did, 3.6% of local buildings had solar panels.