ESSaver PUE is a computerprogram that softwarematically monitors the energyusage for servers. The calculation model is patented. For a couple of years, datacenters have been striving to decrease their power consumption. This power consumption is rising dramatically, as the demand for fast online data increases exponentially throughout the world. ESSaver PUE consists of a monitor application, which is installed on every server in a datacenter and a reporting tool, that creates the reports and insights . The monitor collects powerusage data for every (active) process. These usages and savings data are daily uploaded by each server in the datacenter, to a central database (using a webservice, kicked off by the windows or linux scheduler. The site manager can review these usage and savings data via management reports. Using this data, he/she can take action to optimize server deployment and hence minimize waste and disusage and increase the Power Usage Efficiency of the datacenter. The data can also be used to bill customers not on the hardware they use, but on the amount of usage, the software is using.