As server density has increased over the years, power consumption has become significant factor in the data center. It can be easy to forget about this particular aspect of the colocation package, but it is just as vital as space, bandwidth, and the other high-profile factors.
Fortunately, there are a few tools available that make it a bit easier to determine what your power needs are. Connex measures power usage in the form of Amperes drawn at standard line voltage. Determining how many amps you need at the outset will allow you to get an accurate quote for your needs, and can save a lot of trouble and headache down the road.
If you are using Dell equipment, you can use the Dell Datacenter Capacity Planner or the Energy Smart Solution Advisor to determine the power needs for your equipment. These online tools let you load your equipment model into a workspace, edit it to match your configuration, and set the level of loading. You can then can read the total Amps needed (ignoring watts because that figure includes heat dissipation). Simply do this for each piece of Dell equipment you will be using, and add all the values together to determine your total amps required. Please note: unless otherwise indicated, cabinet power will be supplied as 115V, so be sure to set the Properties of the DCCP for that line voltage before proceeding with measurements.
Access the DCCP and ESSA here: http://www.dell.com/content/topics/topic.aspx/global/products/pedge/topics/en/config_calculator?
HP has a similar tool here: http://h18004.www1.hp.com/products/solutions/power/advisor-online/HPPowerAdvisor.html
If you are using some other brand or custom-made hardware, it may not be as easy, but if you are unable to get published ampere-draw data for your equipment, obtain a consumer power meter like the Kill-A-Watt, which costs about $25 and can be had at many hardware and home improvement stores. You can use this to take an actual reading of the equipment in use, preferably while it is doing some kind of work or running load-testing software.
While gathering this info will take a bit of time, it is well worthwhile. Getting a quotation for your real needs is highly preferable to a guess, and can save you a lot of consternation later.