Industrial AC Energy Cost Estimation

I need a concise yet reliable calculation of how much electricity our air-conditioning system consumes each month and what that translates to on the utility bill. You will receive a datasheet for the cooling units on site along with their numbers together with its cooling capacity and manufacturer-stated power draw. As well as area for each facility.

Because our plant does not keep the air conditioners running at a fixed schedule, the model has to accommodate variable operating hours that change with weather and production load. I will supply recent run-time logs and ambient temperature data so you can weight each unit’s contribution realistically.

What I expect from you
• A clear method—preferably in Excel or Google Sheets—where I can plug updated hours and tariff rates and instantly see kWh consumption and cost for the month.
• A short written summary (PDF or Word) explaining the formulas, assumptions on part-load efficiency if you use any, and a quick sensitivity check showing how costs rise or fall with longer operating hours.

If you are comfortable incorporating local electricity tariff structures (step rates and demand charges) please mention it, as that will make the estimate even more meaningful.