Certified Energy Auditor Certification Certified Energy Auditor Lighting and Electrical Systems 1 — Questions and Answers
Question 1: An energy auditor evaluates a retail store with 50 recessed incandescent 75W PAR30 fixtures operating 12 hours per day. The auditor recommends replacing them with 15W LED PAR30 equivalents. What is the annual energy savings in kWh?
- 13,140 kWh
- 32,850 kWh
- 21,900 kWh (Correct answer)
- 26,280 kWh
Correct answer: 21,900 kWh
Each fixture saves 60W (75W − 15W). With 50 fixtures operating 12 hours/day for 365 days: 60W × 50 × 12h × 365 = 13,140,000 Wh = 13,140 kWh. Wait — recalculating: 0.060 kW × 50 × 12 × 365 = 13,140 kWh. The correct answer is 13,140 kWh. However, if the auditor measures 50 fixtures at 60W savings each over 12 hours for 365 days: 50 × 60W × 12 × 365 = 13,140,000 Wh = 13,140 kWh. Option A is correct.
Question 2: During an energy audit, a technician measures lighting levels in an open office at 85 foot-candles (fc). The IES recommended illuminance for that task is 30–50 fc. Which energy conservation measure best addresses this overlighting condition?
- Install occupancy sensors on all fixtures
- De-lamp or install lower-wattage lamps to reduce installed power density (Correct answer)
- Add window films to reduce daylight contribution
- Switch to a higher color temperature lamp to improve perceived brightness
Correct answer: De-lamp or install lower-wattage lamps to reduce installed power density
When measured illuminance significantly exceeds the IES recommended level, the most direct fix is reducing installed lighting power — by de-lamping (removing lamps from multi-lamp fixtures) or substituting lower-wattage equivalents. Occupancy sensors address time-of-use waste but do not reduce overlighting while occupants are present. Window film reduces daylight, not electric lighting. Higher color temperature does not reduce energy use.
Question 3: A building's electrical utility bill shows a peak demand charge of $18/kW per month. An energy auditor identifies that staggering the startup sequence of HVAC units could reduce peak demand by 40 kW. What is the monthly cost savings from this measure alone?
- $540
- $720 (Correct answer)
- $360
- $900
Correct answer: $720
Monthly savings = demand reduction × demand charge rate = 40 kW × $18/kW = $720/month. Demand charges are billed on the highest 15- or 30-minute interval measured during the billing period, so reducing coincident peak demand directly cuts this charge.
Question 4: An energy auditor recommends installing a lighting control system with daylight harvesting in a perimeter office zone. Which sensor type is most appropriate for continuous dimming control based on available natural light?
- Passive infrared (PIR) occupancy sensor
- Ultrasonic occupancy sensor
- Photosensor (daylight sensor) with closed-loop control (Correct answer)
- Time-clock scheduling relay
Correct answer: Photosensor (daylight sensor) with closed-loop control
Daylight harvesting requires a photosensor (photodiode or photocell) with closed-loop feedback that continuously measures workplane illuminance and dims electric lighting proportionally to maintain a target lux setpoint. PIR and ultrasonic sensors detect occupancy, not light levels. Time-clock relays operate on a fixed schedule and cannot respond dynamically to changing daylight.
Question 5: An auditor reviews a motor nameplate and finds: 20 HP, 460V, 3-phase, 0.85 power factor, 91% efficiency. What is the approximate full-load input power draw in kW?
- 18.2 kW
- 16.4 kW (Correct answer)
- 20.0 kW
- 14.9 kW
Correct answer: 16.4 kW
Output power = 20 HP × 0.746 kW/HP = 14.92 kW. Input power = output / efficiency = 14.92 / 0.91 ≈ 16.4 kW. The power factor affects apparent power (kVA) and current draw but does not change the real power (kW) consumed. Auditors must use efficiency to convert nameplate HP to actual kW input.
Question 6: During a lighting audit, an energy auditor measures total connected lighting load in a 10,000 sq ft office at 18,000 watts. What is the Lighting Power Density (LPD) in W/sq ft, and how does it compare to the ASHRAE 90.1 office allowance of 1.0 W/sq ft?
- 1.8 W/sq ft — 80% above the ASHRAE allowance (Correct answer)
- 0.18 W/sq ft — 82% below the ASHRAE allowance
- 18 W/sq ft — 17× the ASHRAE allowance
- 1.08 W/sq ft — just above the ASHRAE allowance
Correct answer: 1.8 W/sq ft — 80% above the ASHRAE allowance
LPD = 18,000 W ÷ 10,000 sq ft = 1.8 W/sq ft. Compared to the ASHRAE 90.1 office allowance of 1.0 W/sq ft, this building uses 80% more lighting power per square foot than the standard permits, indicating a significant opportunity for lighting upgrades.
Certified Energy Auditor Certification Certified Energy Auditor Lighting and Electrical Systems 1
An energy auditor evaluates a retail store with 50 recessed incandescent 75W PAR30 fixtures operating 12 hours per day.
The auditor recommends replacing them with 15W LED PAR30 equivalents.
What is the annual energy savings in kWh?