Working from home was not really a thing my parents enjoyed when I was growing up. You were either in the office, or you took a sick day.

Today, I work for a publication that doesn't even have an office (well, unless you count the Ars Technica Orbiting HQ). My friends and family who work in offices are often able to work remotely if they need to every once in a while. In fact, the US Bureau of Labor Statistics (BLS) notes that in 2016, 22 percent of employed Americans did some or all of their work at home. Although there are good things and bad things about this new reality (who among us hasn't checked work email right before going to bed), all those hours not spent getting to and from offices is adding up.

According to researchers from the University of Texas at Austin, a difference is noticeable as recently as this decade. In a paper published in Joule, the researchers compared data from 2003 and 2012 gleaned from the American Time Use Survey (ATUS), which is conducted by the BLS. They then tried to estimate how time spent in different buildings and vehicles translated to energy use based on average residential, commercial, and transportation energy use figures from both years.

They found that on average, Americans spent 7.8 more days at home in 2012 than they did in 2003, a significant shift. That time appeared to be subtracted from time spent in non-residential buildings (6.7 fewer days in offices and stores) and time spent traveling (roughly 1.2 fewer days traveling per year). When they were at home, Americans reported increased time working from home, streaming video, or just generically using their computers.

The paper notes that while more time at home translates to more energy use at home, overall energy use fell, especially due to reduced time driving. Driving, the study notes, is just about the most energy-intensive activity per minute that you can engage in, among the 465 activity options available on the federal time-use survey.

Who’s using energy and where?

The researchers also broke out the time-use data based on age and employment status. Unsurprisingly, the populations at either end of the surveyed age spectrum showed the most interesting results. "The population aged between 18 and 24 shows the most dramatic change, [with] 14 additional days at home in 2012 compared with 2003, balanced by 4 days less traveling and 10 hr less time in non-residential buildings," the paper states. "Notably, for the population aged >65, time spent in residences decreased, with more time in non-residential buildings and traveling." While the former might be attributed to a larger student population or more young people working part-time in the "gig economy," the researchers suggest people over age 65 are spending less time at home because they're retiring later.

To get a more accurate picture of how time at home affected energy use, the researchers also looked at how the residential sector changed between 2003 and 2012. Specifically, they used third-party survey data to study the energy-use effects of a growing population, larger home sizes, and energy efficiency measures, as well as increased time spent at home. Overall, energy efficiency measures were key to limiting the effect of increased time spent at home. They estimated that the increased hours at home led to consumption of an extra 480 trillion BTUs (British Thermal Units).

In the commercial and transportation sectors, the story was a bit different. Energy efficiency and reduced time in those sectors led to less energy consumption, despite a growing population and growth in store area. Non-residential sectors of the economy used 1,000 trillion fewer BTUs in 2012 than in 2003, and the transportation sector used 1,200 trillion fewer BTUs.

Accounting for the additional 480 trillion BTUs consumed in homes, that means time-use changes reflected a net decrease of 1,720 trillion BTUs in 2012 from 2003, or 1.8 percent of national primary energy use. "To paraphrase in colloquial terms, Americans are saving considerable energy by staying more at home," the paper stated.

Of course, there are lots of other ways energy is used in the US. And energy use that isn't accounted for in the time-use survey won't show up in this analysis. For example, if more data centers pop up around the country, that energy use isn't accounted for (besides in that small sector of the population that will spend extra working days at a data center, and even then their time will generically be counted as "non-residential" time). Indirect energy consumption from manufacturing processes is also not taken into account in this study (that laptop took a lot of energy to create). All this means that even as Americans use less energy, other sectors of the economy could offset those gains in efficiency.

The results of the study suggest that energy efficiency standards for electronics and appliances can go a long way to cutting energy consumption in the US even further. Same goes for transportation. Efficiency generally isn't the most exciting part of the energy industry, but unless there's a sea change in how Americans spend their time, it's a good way to whittle down carbon emissions from an energy sector still largely dependent on fossil fuels.

Joule, 2018. DOI: https://doi.org/10.1016/j.joule.2018.01.003 (About DOIs)