A Power Unit is a measurement of relative CPU power used in the Enterprise CPU Utilization report. The total Power Units value is calculated by multiplying the number of CPUs (or cores) and the MHz speed to provide the total number of MHz available on the server.
The Power Unit is used to provide more information to simple CPU utilization by adding a total power value. For example, if two servers are both running at 95% CPU utilization, it would be important to understand if one of those servers is a single CPU 2 GHz processor whereas the other is a quad CPU 2.4 GHz server. In this case, 95% of the quad server represents far more workload than 95% of the single CPU server.
The Power Unit measurement does not attempt to relate power between different CPU architectures. For example, a 1.4 GHz POWER4 processor may have more native computing power than a 2.4 GHz Xeon processor but the Power Units display will not take that into account. Therefore it is often more valuable to select servers with the same architecture in a single Enterprise CPU utilization report to ensure that there is no confusion between actual computing power across CPU architectures.