Energy Management
Energy Management
This domain tests how you turn energy data into decisions: setting baselines, normalizing for drivers, screening measures, and reporting savings. Expect questions on power versus energy, load factor, energy intensity, audit levels, and the ISO 50001 cycle.
Core rules
- Power (kW) is instantaneous; energy (kWh) is power integrated over time. A 10 kW load for 5 h uses 50 kWh.
- Load factor = average demand / peak demand over a period. Low load factor means peak-driven cost.
- Baselines must be adjusted for weather, production, occupancy, or schedule before claiming savings.
- ASHRAE audit levels: Level 1 walk-through, Level 2 survey and analysis, Level 3 detailed capital analysis.
- ISO 50001 uses energy review, significant energy uses (SEUs), energy performance indicators (EnPIs), objectives, and continual improvement.
Worked example
A 15 kW motor runs 4,000 h/year at 75% average load. Annual energy = 15 × 0.75 × 4,000 = 45,000 kWh. At $0.10/kWh, energy cost is $4,500. A VFD is projected to cut consumption 20%, saving 9,000 kWh and $900/year. If installed cost is $2,700, simple payback = 2,700 / 900 = 3.0 years. Demand-charge savings are excluded unless the load profile shows a coincident peak reduction.
Traps
Do not multiply nameplate kW by hours without a load factor. Do not call a change in bills savings if production or weather changed. Keep kWh and kW separate, and state the measurement boundary.