Yahoo: Data centers use two to five percent of all the power created in the US during any given year. Using 2013 as an example, the Natural Resources Defense Council estimates the amount of power used by US data centers was 91 billion kWh. Peak demand One area that's been a struggle for operators is balancing the number of servers needed to meet peak demand vs. the cost of having servers powered up and standing by in case of a computing surge. Depending on the sources cited the electricity wasted to power...