Well, I am sure power is very important when designing datacenter. How much AMP is needed for each cabinet, For 45U cabinet, how much amps minimum needed.
Power and Power Distribution is usually the main thing that limits the size a data center can grow to. It is often the cost or availability that determines where you can build a data center or how many servers you can install. Everyone tends to think it's bandwidth availability. In fact that is one of the smaller considerations. It only takes money to get fiber run to your building. Power at the levels of a data center take quite a bit of planning with the local utility company, and often city planners. A large data center will use many thousands of amps for their services and it's not like you can just call up the power company and say, "he guys can you just run me another 800 amp 3 phase line today. "
Most racks have power in 15 or 20 amp increments, rarely over 40 amps. We use a rating of 1.25 amps per power supply to determine the load planning.
Generally speaking most DC owners have spec'd out thier cabinets to have a max of 2 x 20 AMP 's. The new centers being built are building out for 3 x 30 AMP for those of us who like put 45 DUAL Xeon's and slap the switch on top of the cabinet.
Power is directly related to cooling also, so you need to make sure that you can provide proper airflow to cool the power in each cabinet also. I believe that Class 5 DC's are spec'd at cooling 150 Watt's per SQFT, (correct me if I'm wrong here).