From Scott Carlberg

Our blogs have looked at ways that consumers can save energy in their homes or businesses. There’s something about energy, though. It is a complex thing, and not just under one consumer’s control.

Time to expand our thinking. ECC is doing this blog just to point out how involved saving energy in a society can be. Here’s an example that goes through several calculations of energy efficiency.

Let’s start with buildings. Energy Use Intensity is a measure of a building’s yearly energy use per unit area, like an amount of energy per square foot. Some people measure the EUI by the amount of energy used at the building site. Others will include the fuel that an electric generating plant may use to satisfy the building.

Apples-to-apples measurement is a reason to look at EUI, which can allow one building’s efficiency be compared to another. Which building is a smarter energy user? A better energy user is likely to have a lower cost to operate. That can be great news, but there is another energy factor to consider that adds a whole new variable.

Under construction – neat new building and parking. Buildings and cars use energy

A concept noted recently in a TreeHugger post – Why the Transportation Energy Intensity of buildings matters – adds a pragmatic new angle to building efficiency. The idea is that the people who use the building have to use energy to get to the building, and that is often by personal vehicles versus walking or public transportation. So if an energy efficient building is 20 miles further each way for 500 workers to travel, for instance, that can add 40 miles a day for each worker, or 20,000 more miles a day for all employees, or 100,000 miles a week for those employees.

Let’s do some math. Kelley’s Blue Book says that one of the most gasoline-efficient sedans in 2019 will average 42 combined city/highway miles per gallon. (By the way, 22 miles per gallon is more average in the country, so we are using a best case example here.)

  • Each worker daily: 40 miles @ 42 miles per gallon. That is under an extra gallon of gasoline used.
  • 500 workers daily: 20,000 miles @ 42 miles per gallon. That is 476 extra gallons of gasoline.
  • 500 workers weekly: 100,000 miles @42 miles per gallon. That is 2,381 gallons of gasoline.

Motor fuel to get to an energy efficient building still affects overall energy efficiency

When gasoline is burned it puts emissions into the air. When extra gasoline is burned, there are more emissions created. The U.S. Government fuel figures say, “It seems impossible that a gallon of gasoline, which weighs about 6.3 pounds, could produce 20 pounds of carbon dioxide (CO2) when burned. However, most of the weight of the CO2 doesn’t come from the gasoline itself, but the oxygen in the air.” So 2,381 gallons of extra gasoline burned could feasibly put almost 50,000 pounds of of carbon dioxide in the air.

There’s another math angle, too. There are about 250 workdays in a year. If a worker buys an extra gallon of fuel fro work each day, that is an extra $500 of personal cost at $2/gallon. The average cost per gallon in the U.S. in 2017 was $2.42/gallon. That is $605 extra dollars a year for each driver. In 2013 the average gasoline price was $3.51, or $877/year.

Be sure, these figures are variable because cars get different gasoline mileage, there are hybrids, electric vehicles, and in the case of the office building, some people may walk to work or take public transportation.

Numbers like this are tough to comprehend since we don’t deal with them daily. The concepts hold tight, however: Energy use and efficiency is a complex formula. Much of energy efficiency depends on our individual habits, and some is out of our immediate control. Some answers: Monitor personal transportation energy use, take public transportation if possible, use work-at-home options to eliminate transportation if possible, for instance.