Google released its number this morning: 2.2 billion kilowatt hours. That’s how much energy it used last year. That’s one hundredth of one percent of global energy use. Of the 1.46 million metric tons of CO2 that Google produced last year, most of it came from data centers, and Google has said that number would be double without efficiency measures. Perhaps the most interesting info coming from the site that Google built to communicate its energy use was how aggressively it argues that PUE (Power Usage Effectiveness) needs to be measured as often as possible and over a 12 month period. We’ve covered the issues with PUE as a metric for how efficient a data center is, but one of the core problems is that companies take PUE measurements during cold months when cooling costs are low. Measuring it monthly or even daily over the course of a year will give the most honest data on how efficiently a data center is functioning.