Kilowatts and kilowatt-hours are different things
A kilowatt is a rate: how fast power is being drawn at a moment. A kilowatt-hour is a quantity: how much energy was drawn over time. A facility that draws 100 kW for 10 hours has used 1,000 kWh. The bill charges for the kilowatt-hours as consumption, and on most commercial tariffs it also charges for the highest kilowatt figure the facility reached, which is the demand.
The two answer different questions. Consumption says how much the facility used. Demand says how hard it pulled at its worst moment, and that moment is what a service has to be sized for, because a service is rated in amps and it fails at its peak, never at its average.
Where demand appears on the bill
On a demand-metered account there is a line for it, usually labelled demand or maximum demand, in kW or sometimes kVA, with the interval and often the date and time it occurred. The interval matters: the utility does not record the single highest instant, it records the highest average over a fixed window, commonly 15 minutes, and that averaged figure is the demand.
Not every commercial account is demand-metered. Smaller accounts are often billed on consumption alone, and their bills show kilowatt-hours and nothing else. That is the case that matters for a load study.
Why a load study needs it
NEC 220.87 establishes the existing load on a service from its maximum demand: the highest demand over 12 months of utility records, taken at 125%, plus the new load, against the rating. Twelve months of consumption figures cannot supply that. They say how much energy was used each month, and nothing about the peak rate inside the month. A facility with kilowatt-hour bills alone has no usable record for the utility data path.
That does not end the study. The section's other path is a 30-day recording at the panel, which produces the demand figure directly, at the same 15-minute interval the code specifies. And before that, it is worth checking the utility portal: many accounts hold interval data the bill never printed, and an account that looks consumption-only on paper sometimes has a year of demand data online.
How to tell which kind of bill you have
Look for a line in kW or kVA. If the only unit on the bill is kWh, the account is billed on consumption and there is no demand record to send. If there is a kW line, 12 months of those bills are the evidence a measured study needs, and the question is answered from records in days rather than from a recording in weeks.
Questions people ask
Is kW the same as kWh?
No. A kilowatt is a rate of draw at a moment. A kilowatt-hour is energy used over time. Demand is measured in kW. Consumption is measured in kWh.
My bill only shows kWh. Can I still get a load study?
Yes. The existing load is recorded at the panel over 30 days instead of read from records, and the study takes about 5 weeks rather than days. Check the utility portal first: some accounts hold interval data the bill never printed.
Where do I find 12 months of demand data?
On the bills themselves, where the account is demand-metered, or in the utility's online portal, which often holds interval data at finer resolution than the bill. Either is evidence for a measured study.
What interval does the code use for demand?
For the 30-day recording path, NEC 220.87 defines the maximum demand as the highest average over a 15-minute interval. Utility billing intervals vary, and 15 minutes is common.