The most energy-efficient way to watch movies? Stream on
A study shows that energy savings come from eliminating transportation and inefficient DVD players.
Watching a live stream of a movie can be more energy-efficient than watching the movie on DVD, especially if the latter involves driving to a rental or retail store to rent or buy the DVD, reports a study by researchers at Northwestern University and Lawrence Berkeley National Laboratory (Berkeley Lab).
Comparing different ways to watch movies
Researchers studied five different ways of viewing movies and, using a systematic method called life cycle analysis, estimated the energy used and carbon dioxide emissions produced for each. They determined that video streaming can be more energy efficient and emit less carbon dioxide than the use of DVDs, depending on the DVD viewing method.
“End-user devices are responsible for the majority of energy use with both video streaming and DVD viewing,” said Eric Masanet, associate professor of mechanical engineering and of chemical and biological engineering at Northwestern’s McCormick School of Engineering and Applied Science.
“Much of the energy savings estimated in shifting to video streaming comes from shifting end-user devices to more energy-efficient alternatives — in other words, away from old DVD players,” he said.
The study was published May 28, 2014, in the journal Environmental Research Letters. The authors are Masanet, Arman Shehabi of Berkeley Lab and Ben Walker of Northwestern.
“It’s a modern-day equivalent of the debate about which is more environmentally sound — the disposable or the cloth diaper?” said Shehabi, a scientist at Berkeley Lab.
The researchers compared five basic movie-viewing cases:
Watching a movie live-streaming over the Internet
Renting a DVD through a mail-based service
Renting a DVD at a local store
Buying a DVD from an internet source and receiving it in the mail
Buying a DVD at a local store
Estimating the life-cycle energy use of the various cases required accounting for the energy used to manufacture DVDs; to transport DVDs by mail truck; to drive to and from local stores and rental locations; to stream movies over the Internet; and to manufacture and operate the in-house devices ultimately used to watch the movies.
“Video streaming is favorable when compared to any DVD viewing involving consumer driving, which significantly increases the energy and carbon dioxide emissions per viewing hour,” said Walker, a master’s student studying energy at Northwestern and sustainability and a member of Masanet’s research group.
The study esitmates that the total video viewing in the United States in 2011 required about 192 petajoules of primary energy and emitted about 10.5 billion kilograms of carbon dioxide. Shifting all DVD viewing in 2011 to video streaming would have reduced the total primary energy use to about 162 petajoules and the carbon dioxide emissions to about 8.6 billion kilograms. This figure represents a savings equivalent to the primary energy used to meet the electricity demand of nearly 200,000 U.S. households each year.
The study also shows that data transmission energy and consumer travel account for significant portions of the total streaming video and DVD viewing energy use. Streaming data at a higher rate to support complex video increases the energy use of streaming beyond that of DVD viewing. Reducing the consumer energy use of travel to and from store locations makes the DVD viewing of movies more energy-efficient than streaming.
Shehabi believes the research can guide the electronics sector to greater efficiency. “Our study suggests that equipment designers and policymakers should focus on improving the efficiency of end-user devices and network transmission energy to curb the energy use from future increases in video streaming,” he said.
“Innovation can help video entertainment evolve towards becoming a more environmentally sustainable service,” Shehabi said. “Such efficiency improvements will be particularly important in the near future, when society is expected to consumer far greater quantities of streaming video content compared to today. In other words, to maintain the environmental efficiencies of streaming video, we need to continuously improve efficiency to offset the effects of rapidly growing video demand.”