Wow, basic electricity 101. First get straight on your terms, you are mixing them.

Power is expressed in kilo-Watts or kW.

1HP = .746 kW (746 watts)

If you use power over time, that is called "Energy", and is expressed in kWH, or kilo-Watt Hours.

So energy in kWH = kW x Hours used.

But if all you know is the HP ratings of the motors, the best you can determine is the MAXIMUM power consumption, in other words what they would consume if they were fully loaded. Any AC motor will consume only as much power as the connected load demands of it to do the work involved (less efficiency). If you have a kW meter attached, then you can determine the actual power consumption. Without it, you can only guess, or maybe estimate.

If you can measure the current and you know the nominal voltage, you can estimate the power consumption. The formula for 3 phase motors is as follows:

kW = V x A x PF x Eff x 1.732/1000 where;

V = nominal or measured Voltage

A = Current in Amperes

PF = Power Factor, and if you don't know what it is, you can estimate .70 conservatively

EFF = the motor Efficiency rating and again if you don't know what it is, you can estimate it at 80% conservatively.

1.732 is the sq. root of 3, because it is 3 phase power. If it were single phase, you ould leave out that step.