Add up the total wattage or amperage if everything ran at 100%.
Utilities do not charge for a lightning-fast surge (e.g., starting a 200kW motor for 2 seconds). Instead, they measure the sustained load over a sliding window. If your load peaks for 5 minutes and drops to zero, the 30-minute average will be modest. However, if you sustain high load for the entire window, your MD spikes. maximum demand calculation