Benchmarking buildings for energy consumption is an industry buzzword, like “sustainable” and “green”. Benchmarking is based on energy intensity, which is energy consumption per square foot of floor space, like automobile miles per gallon. That is where the similarities end. The vast majority of cars burn gasoline, and they serve a very similar purpose. Buildings use electricity, and in most cases, any of the following: natural gas, fuel oil, steam, chilled water and sometimes more exotic sources like wood or flux capacitors running on Pepsi cans and banana peels.
Garden variety benchmarking tells building owners little, at best, and it almost always lacks actionable direction for tackling the issues that make some buildings energy hogs.
Physically speaking, the fitness of a commercial building is like the fitness of a human being. If you ask me for the fitness level of a 200 pound human and all you tell me is the gender is male, I would have to ask, is he like this guy or this guy:
Pictures tell a thousand words in this case. Not so with buildings. What is the building type? What types of fuels does it consume? What types of heating and cooling systems does it have? Anyone who knows real buildings understands clear cut answers to these questions are about as rare as Mario Balotelli’s physique.
Characterizing buildings from answers to these questions is a mess. There may be many additions, each with unique heating and cooling system types; some sections may lack ventilation; there are frequently multiple meters; there may be hybrid gas/electric systems. A good benchmarker can read building, system, and operating characteristics described by the building owner, look at the energy bills, and make informed estimates of potential savings – much like a doctor interviewing a patient and taking vital signs screens for ailments.
What is the Problem?
The British, as in the British thermal unit (Btu), the “universal” unit of energy; the equalizer – that is one big problem. Many benchmarkers mix Btu electric with Btu fossil, or even thermal Btus. A kilowatt hour has 3413 Btu. A therm of natural gas has 100,000 Btu. A pound of wood has 8600 Btu. Do you suppose a kWh or a four pound hunk of wood is more valuable?
At 10 cents per kWh, a million Btu of electrical energy costs about $30. At 60 cents per therm, a million Btu of natural gas costs $6. Does mixing electrical Btu with natural gas Btu make sense? Even dollars per square foot isn’t worth much because it doesn’t indicate which fuel or both/all fuel consumption is high. Benchmarking needs to reveal whether the electrical, fossil, or thermal energy use is high, and by how much, and what the excess is worth.