Size Facebook by power usage.
180,000 servers 2018

Based on data available for total annual power draw for Facebook's data centers - 509 million kilowatt hours -
 and estimates Facebook's average data center power usage at 58 megawatts of power.
He then applies Facebook's published Power Usage Effectiveness (PUE) of 1.07 to
conclude that the social network is delivering 54.27 megawatts to servers, and divides that by
the power usage of an efficient server. At 300 watts per server, that works out to about 180,000 servers.

Facebook’s electricity consumption has gradually increased over the last years, reaching 3.43 terawatt hours in 2018. Facebook has set goals to reduce its greenhouse gas emissions by 75 percent in 2020. In recent years, the company was able to separate growth in the business from increased emissions, reducing their greenhouse gases from the previous year. The technology company is also aware of its water consumption and has committed to a circular system that allows for the reuse of water consumed. By analyzing their value chain and implementing changes into the supply chain, Facebook has been able to mitigate emissions from their operations.