Americans are saving energy because they don’t go outside as much anymore, researchers say. It’s a plus for the environment, though in another light (no pun intended), it’s just sad.

In 2012, Americans spent an extra eight days at home compared to 2003, according to the American Time Use Surveys. Being at home means using more energy by keeping the lights on and watching TV. But it also means less travel, and it means that fewer people are outside operating offices and stores. So overall in 2012, we saved 1,700 trillion British thermal units (BTU) of heat, or 1.8 percent of the national total, according to an analysis published today in the journal Joule. That’s about how much energy Kentucky produced in all of 2015.

Specifically in 2012, Americans spent one day less traveling and one week less in buildings other than their homes when compared to a decade earlier. The trend of staying indoors is especially strong for those ages 18 to 24: the youths spent 70 percent more time at home than the general population. At the other end of the age spectrum, those 65 and older were the only group that spent more time outside the home compared to 2003. Next, the researchers want to look at energy consumption changes in other countries as a result of lifestyle changes.

It’s tricky to pinpoint the exact reasons for these changes, but the authors suggest it’s a combination of remote work and services like streaming video and online shopping. With the rise of flexible work-from-home privileges, Amazon Prime, two-day shipping, and Netflix, there seems to be fewer and fewer reasons to venture outside the front door. But scientists have long said that spending time outdoors is good for us. Being in nature is helpful for reducing stress, and going to see a friend helps us maintain relationships, which is also key for well-being. Reducing energy use is a good thing, but so is going out into the world every once in a while.