In 2011, a large study found that data centers probably used about 1.3 percent of the world's electricity between 2005 and 2010. Since then, many studies have come out, but many of these studies have overestimated future energy use. One study claimed that data centers will use 20 percent of all electricity by 2025, said Kamiya. He said that the media often focuses on worst-case scenarios.

However, Masanet's new study gives solid estimates of the energy used by data centers. These estimates have been reviewed by experts. Kamiya said that key decisions around climate and energy have to start with facts and data.

The demand for data is constantly growing, especially given the growth of advanced technologies. Experts think that computer use will double as more people come online around the world. However, researchers estimate that data centers will be able to cover these growing needs. They predict that data centers will continue to improve their energy efficiency in the future.

To make sure computers use energy efficiently, several things need to happen, Masanet said.

Industry and governments need to continue to encourage energy efficiency. Nations also need to be open about how much energy their data centers use. This is particularly true for countries in Asia, where data center energy is expected to grow but little information is available, Masanet said.

Large data companies also need to source their electricity from renewable energy. This is energy that is collected from renewable resources, which are naturally replenished on a human timescale, such as sunlight and wind. Google and Apple both purchased or generated enough renewable electricity to match 100 percent of their data center energy use in 2018. Facebook says it will reach 100 percent this year.

"It's not that we can be complacent," said Masanet. "But we don't have to feel guilty about watching Netflix or staying connected."