Client's PSE&G bill shows a power factor of 0.72 with a substantial penalty. The client hired an electrician to measure PF at the main panel and got 0.91. That's a massive discrepancy. The client wants me to challenge the utility's reading. How do I resolve conflicting PF measurements?
Utility says PF is 0.72 — client's electrician says 0.91 — who is right?
The discrepancy is probably a timing issue. The utility's PF reading is the average over the entire billing period, weighted by demand. The electrician's reading is a snapshot at one moment in time. If the building's PF is 0.91 during normal hours but drops to 0.60 during startup or shutdown periods, the utility's monthly average could easily be 0.72. Ask the electrician to install a PF data logger for a full week to get a continuous reading. That will show the PF profile over time and explain where the low readings occur.
Derek's explanation is the most likely. But also consider the possibility that the utility's meter is reading incorrectly. Request a meter test specifically for the reactive power (kVAR) register. If the reactive register is malfunctioning, the PF calculation based on that register will be wrong. I've seen reactive meters fail while the real power (kW) meter was fine — the result is an artificially low PF reading that generates a penalty the customer doesn't deserve.
I had a similar discrepancy on a Duke account. Turned out the CT feeding the reactive register was wired incorrectly after a meter swap. The PF reading was essentially random. Meter test confirmed it and the client got 2 years of penalties refunded — about $34,000.
Requested the meter test. If the reactive register checks out fine, I'll go with the data logger approach to identify when the PF drops. If the meter is bad, we're looking at a big refund. Will update.