How Americans watch movies has changed dramatically over the last century. Once restricted to theaters, movies have long since moved into our homes. And though some families might still have ancient VCRs or LaserDisc players hanging around, most of us now watch movies on DVDs or films streamed over the Internet.
For many people, the choice of DVD or streaming movie tends to be one of convenience. But there’s one winner when it comes to energy use — video streaming. The main culprits? Energy-inefficient DVD players and the vehicles used to transport DVDs from store to home, report Arman Shehabi of Lawrence Berkeley National Laboratory in Berkeley, Calif., and colleagues. Their study was published today in Environmental Research Letters.
Americans watch a lot of movies, older TV shows (Breaking Bad marathon, anyone?) and other videos in their homes. In 2011, for instance, people in the United States watched about 17.2 billion hours of DVD content and 3.2 billion hours of video streamed over the Internet.
In the new study, Shehabi and colleagues used data from 2011 to look at the energy consumption involved in watching DVDs purchased in a store or through the mail and rented in a store or through the mail, and compared that to Internet streaming. “Energy consumption” here is more than the amount of energy used to play the movie on a screen—it includes all the energy needed to get a movie from Hollywood to home, including DVD manufacture, shipping and delivery, storing files on data servers and methods of playback and viewing. By including these other factors, researchers could calculate the average amount of energy consumed for each hour a movie after it’s production.
Video streaming cost about the same amount of energy as DVDs purchased or rented through the mail, Shehabi and colleagues calculated. Each of those methods of viewing consumed almost 8 megajoules of energy per hour of watching.
But DVDs rented or purchased in a store consumed a significant amount more (12 megajoules and 10.6 megajoules, respectively). In other words, getting DVDs from a store came at a higher energy cost.
This cost translates into a whole lot of increased carbon emissions. How much exactly? Well, if everyone who watched DVDs in 2011 has instead streamed those videos, that would have avoided some 2 billion kilograms of carbon dioxide emissions and saved about 30 petajoules of energy. That’s enough energy to power 200,000 U.S. households for a year, the researchers calculated.
Obtaining DVDs from a store is so much more energy-intensive because most people drive to get there. Mailed DVDs are also driven to your home by the mailman, but there’s considerably less driving involved—many movies can be delivered to different addresses on the same route whereas renting from the store involves each individual driving to the store and back twice (once to rent, and once to return).
But the other big energy-suck when it comes to DVD viewing is the DVD player used at home, Shehabi’s group found. DVD players sit around for days or even months on end, using up lots of energy, even when turned “off.” (The easiest way to get around this is to unplug the device when it’s not in use, but that comes at a loss in convenience.) Older versions, in particular, are big energy guzzlers.
Movies streamed at home usually depend on more-efficient, newer devices. That helps to offset the energy consumed in transmitting the video data over the Internet, the largest source of energy use for this method of viewing.
Perhaps surprisingly—given how data centers are perceived as huge energy sinks— storing those movies and television shows in the cloud isn’t a huge contributor to energy consumption in this equation. They account for less than a percent of video streaming energy use, the team calculated. That’s because even though a data center can use a huge amount of energy, lots of data is stored in that one place, and lots of people are using that video data. So once it’s averaged out, data centers contribute just a tiny bit of energy consumption to a single movie.
Even though the authors’ analysis was done using numbers from 2011, their calculations are likely already outdated. Blockbuster may be dead, but DVD rental stores remain. Digital movie streaming and purchases increased last year; DVDs declined. Video streaming is becoming more efficient, thanks to set-top boxes like Roku and Internet-enabled televisions. Those energy efficiencies could be offset, however, by increases in streaming of more complex—and more energy-demanding—video content.
Who knows what’s next? Perhaps whatever follows the VCR and DVD and video on-demand will be an even more energy-efficient way of keeping us entertained at home.