Data Collection & Analysis
Match the instrument to the question
The data hierarchy runs from utility bills (12–36 months, low resolution, essential for baseline) to interval data (15-minute, ideal for load shapes and demand analysis) to sub-metering and temporary logging (end-use specific) to trending from the BAS (free but often uncalibrated). Spot measurements describe one instant; trending and logging describe duty cycles. Auditors who measure only once routinely miss cycling equipment, night loads, and weekend operation.
The most common exam-level technical point is the three-phase power equation:
P (kW) = √3 × V (line-to-line) × I (amps) × power factor ÷ 1,000
Equally important: nameplate horsepower is a rating, not a load - verify actual amps against full-load amps to estimate load factor, and note that oversizing is normal. Record measurement conditions, instrument accuracy, and sampling basis; IPMVP-style options (retrofit isolation, whole-facility, calibrated simulation) define how much measurement a savings claim requires.
Traps. Using nameplate kW as measured load; averaging three phases without checking balance; confusing kW with kVA (missing power factor); extrapolating a 15-minute spot reading across a year; and ignoring data quality - meters that are swapped, estimated bills, or time stamps that do not align with the BAS.
Worked example
A 480 V, three-phase motor draws 42 A at 0.85 PF: P = 1.732 × 480 × 42 × 0.85 ÷ 1,000 = 29.7 kW. At 4,000 operating hours per year that is 29.7 × 4,000 ≈ 118,700 kWh - at $0.10/kWh, roughly $11,900 per year.