Phil from Denver. Client's own building management system shows a peak demand of 287 kW for the billing period. The utility bill shows 312 kW. The discrepancy is about 25 kW which translates to about $400 per month at their demand rate. How do I figure out which number is right?
Peak demand reading doesn't match the client's records — where do I start
Lisa from Portland. First question: are both systems measuring at the same point? The utility meter is at the service entrance. The building management system may be measuring downstream after some building equipment that the BMS doesn't track.
The BMS does not include the elevator motor control and the outdoor signage circuit. Those are probably 10 to 15 kW combined.
Lisa again. There you go — that probably explains most of the gap. The utility is measuring the full service entrance load while the BMS is seeing an incomplete picture. Before you file any dispute confirm that the BMS covers every load on the account.
Mark from Houston. Also check whether both systems use the same demand interval. BMS systems sometimes compute peak demand over a different window than the utility's billing interval.
Mark the BMS is set to 15-minute intervals which I believe matches the utility. But I had not checked the meter registry date — I need to confirm the utility is using the same interval.
Mark again. Request the interval data file from the utility for that billing period. It will show every 15-minute reading. You can find the 312 kW peak, see when it happened, and then cross-reference with the BMS log for that exact time window to figure out what drove the discrepancy.