kW required for cooling server room?

We’ve been growing a lot over the past year and have gone from 2 Compaq Proliant 200 servers in a closet to 2 Compaq Proliant 1600, 2 Compaq Proliant 800, 2 Compaq proliant 200, and a couple custom built servers. We’ve moved them out of the small closet and into a bigger, central room (of course). Now we are looking into cooling options because leaving the door open is both not enough to keep it cool and a security risk. In speaking with a few cooling people, they have asked what is the total kW of my servers. How do I find this out? I assume it’s a measurment of heat that they give out over time, but I don’t know where to get this information or if it’s something I can just calculate. Any suggestions would be great! thanks,
Ron