I need to plan an A/C system to offset heat gain from server equipment and other electronics. The rating plates on everything totals 16,000 watts, but how much heat should I count on from these pieces. It isn't all heat, is it?

I think this is a tough question. I wouldn't use nameplate data.

I'd measure the power drawn at the panel.
Now some will be converted to light, some heat and some mechanical energy.

The disk drives and fans will use a 12 V supply and that number can be subtracted out.

Fluorescent ighting can be subtracted out too and there are ways of dealing with lighting.

Don't forget people.

You may also be able to do it by measuring the temperature rise of the space over time.

1 watt equals 3.4121 BTU, always. Heating equipment naturally produces this more efficiently, but there are many well houses here in the Ozarks that are heated by a 100 watt light bulb. And as far as counting out fluorescent lighting... that's not accurate. Because of the lighting in our retail settings, we actually have to start cooling by March 1st. And that is in the Chicago area. Obviously the more efficient the lighting is the less this happens. The lighting load is always calculated in both heating and cooling calculations especially in large operation where people have to work or shop.

A smart HVAC person always allows the engineer to calculate item like this. The reason is very simple. When the system does not work as planned the engineer is on the hook for the problem not you. There are many items that need to be calculated for this setup.

Usually these systems must run 24/7 forever so

A head pressure controller system must be installed for cold weather use. Not some cheap Mickey Mouse control but probably a real set of pressure operated dampers for each outside condensing unit.

The outside condensing units should be of commercial quality not some piece of residential equipment.

Static needs to be addressed since computers/servers hate static so some type of humidity control needs to be included in the job plan.

Space size in volume also needs to be considered since the load calculation will also need to take this into consideration.

If it is a real computer/server area then you will probably have under floor troughs for wire pulling and other uses. That space will also need to be calculated into the figures.

There is more here than meets the eye so again I say contact the engineer for the job OR tell the owners that you can only bid off approved plans. It is all called CYA.

I'm coming late to this thread, but I want to reinforce what Missouri Bound said. For all intents and purposes of questioners here, you can figure that ALL electricity used inside an enclosed space can be calculated as heat. The percentage of energy converted into light or potential energy by motion is so small that it can be ignored.

KISS, you are off base here. Even 12v power is measured in watts. And watts consumed converts into heat released. That is why fans actually increase the heat in the area they are running in. When I took my HVAC classes, we were taught to take the air handler fan into account when figuring system efficiencies.

Ten 100 watt bulbs will heat a room just as fast and efficiently as a standard four foot section of electric heat. And watch those fluorescent lights, they put out more heat than the sum of the tube wattages. You have to count the ballast losses too, and that is significant if you have magnetic ballasts.