Yes watts are watts, but, as is most likely the case in commercial services, there are often demand based charges.
I believe that with demand based charges they record the maximum demand on any of the three lines (assuming 3-phase) that last for more than about 15 seconds anytime during the month, and then the power company charges you a fee based on this demand along with your normal per KWhr fee. The demand portion of the meter is monthly reset.
The demand charges can easily make up the lion share of your bill, especially if you are a low KWhr user. Also if you are unbalanced, these demand charges are multiplied by the peak which is higher than it would be if the system were balanced.
Look at a rate structure for your area. The big users have a relatively low per KWhr charge which is often easily compensated for by the heavy maximum demand charges.
