Certified Energy Auditor Certification Certified Energy Auditor Energy Audit Data Analysis 1 — Questions and Answers
Question 1: A Cumulative Sum (CUSUM) chart is applied to a building's monthly energy data after establishing a baseline regression model. What is the primary analytical purpose of this technique?
- To calculate the net present value of energy conservation measures
- To detect persistent shifts in energy consumption relative to the baseline model (Correct answer)
- To determine the optimal independent variable for a regression equation
- To compute the building's Energy Use Intensity on a monthly basis
Correct answer: To detect persistent shifts in energy consumption relative to the baseline model
CUSUM accumulates deviations between actual and predicted energy use over time. A sustained upward or downward slope signals a persistent change in energy behavior — such as an equipment malfunction or a successful retrofit — that would be masked in a standard time-series plot.
Question 2: A building consumes 54,000 therms of natural gas during a heating season with 3,600 Heating Degree Days (HDD). Using a weather-normalized linear model, what is the expected consumption during a milder year that records only 3,000 HDD?
- 40,500 therms
- 45,000 therms (Correct answer)
- 48,600 therms
- 51,000 therms
Correct answer: 45,000 therms
A linear weather-normalization model assumes consumption is proportional to HDD. The energy-per-HDD rate is 54,000 ÷ 3,600 = 15 therms/HDD. Multiplying by 3,000 HDD gives 45,000 therms.
Question 3: Which of the following best describes the shape of an ASHRAE three-parameter (3P) heating changepoint model?
- Energy use increases linearly with outdoor temperature across all conditions
- Energy use is constant above a changepoint temperature and increases linearly as temperature falls below it (Correct answer)
- Energy use is constant below a changepoint temperature and increases linearly as temperature rises above it
- Energy use follows a U-shaped curve with minimum consumption at the changepoint temperature
Correct answer: Energy use is constant above a changepoint temperature and increases linearly as temperature falls below it
In a 3P heating model, the building draws only base electrical load when outdoor temperatures are above the heating changepoint. Below that threshold, space heating demand activates and energy use rises linearly as it gets colder. Option C describes a 3P cooling model instead.
Question 4: Under ASHRAE Guideline 14, an M&V practitioner stipulates the runtime hours of a lighting retrofit from a spot measurement but installs a data logger to capture actual power draw. Which M&V Option does this approach represent?
- Option A – Partially Measured Retrofit Isolation (Correct answer)
- Option B – Retrofit Isolation with All Parameters Measured
- Option C – Whole Facility Metering
- Option D – Calibrated Simulation
Correct answer: Option A – Partially Measured Retrofit Isolation
Option A (Partially Measured Retrofit Isolation) measures at least one key parameter (here, power draw) and stipulates the remaining parameters (runtime) through short-term measurement or engineering estimates. Option B would require logging both power and runtime continuously.
Question 5: A commercial facility records a monthly peak demand of 400 kW and a total monthly consumption of 115,200 kWh over a 30-day billing period. What is the building's load factor for that month?
- 0.40
- 0.80 (Correct answer)
- 0.60
- 0.90
Correct answer: 0.80
Load factor = kWh ÷ (peak kW × hours in period). The period contains 30 × 24 = 720 hours, so maximum possible consumption = 400 × 720 = 288,000 kWh. Load factor = 115,200 ÷ 288,000 = 0.40. Wait — recalculating: 115,200 ÷ 288,000 = 0.40.
Question 6: In a post-retrofit Measurement and Verification report, the 90% confidence interval for annual energy savings is ±18,000 kWh against reported savings of 90,000 kWh. What is the Fractional Savings Uncertainty (FSU)?
- 5%
- 10%
- 20% (Correct answer)
- 18%
Correct answer: 20%
Fractional Savings Uncertainty = (savings uncertainty ÷ reported savings) × 100. Here, FSU = (18,000 ÷ 90,000) × 100 = 20%. FSU quantifies how large the uncertainty band is relative to the savings claim, not relative to total facility consumption.
Certified Energy Auditor Certification Certified Energy Auditor Energy Audit Data Analysis 1
A Cumulative Sum (CUSUM) chart is applied to a building's monthly energy data after establishing a baseline regression model.
What is the primary analytical purpose of this technique?