About 25 percent of United States electricity goes to businesses, and companies like Google are now about 2 percentage points of that. Dominion Virginia Power, located in a state with perhaps the world’s largest concentration of data centers, last year had a demand increase from those customers of 9 percent, while overall demand was nearly flat, according to Dominion.

Google operates eight different businesses, including internet search engines, YouTube and Gmail, each of which has over 1 billion customers. They run on a global network of 13 large-scale data centers, each one a complex of many buildings containing hundreds of thousands of computers.

The 5.7 terawatt-hours of electricity Google consumed in 2015 “is equal to the output of two 500 megawatt coal plants,” said Jonathan Koomey, a lecturer in the school of earth, energy and environmental sciences at Stanford. That is enough for two 140,000-person towns. “For one company to be doing this is a very big deal. It means other companies of a similar scale will feel pressure to move.”

It moves the needle on costs to have a big consumer, Mr. Koomey added, since a larger market tends to allow for economies of scale and more innovation. “Every time you double production, you reduce the cost of solar by about 20 percent. Wind goes down 10 to 12 percent,” he said.

Facebook has entered into similar deals with wind producers. Last week, Amazon reiterated its long-term commitment to power its machines entirely with renewable energy, though for 2016 it expects to be above about 40 percent of its goal. It has announced five more solar projects.

Microsoft says it has been 100 percent carbon neutral since 2014, but much of this comes from the purchase of carbon offsets, which are investments in things like tree planting or renewables projects meant to compensate for the fossil fuels a company consumes. The company hopes to have half of its electric power supplied from wind, solar and hydroelectric sources by 2018. Its data centers currently use about 3.3 million megawatt-hours of power a year.