The method
Before using the result
- Tariffs, operating hours and costs are user assumptions. Results exclude financing, taxes, demand charges and changes in equipment performance.
Worked examples
These original training examples illustrate the method for Certified Energy Auditor (CEA). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Include maintenance-cost changes when screening an energy project. Explain why a simple-payback result is not a discounted financial appraisal.
- Installed cost (currency units)
- 5,000
- Annual energy-cost saving (currency/year)
- 1,500
- Annual maintenance-cost increase (currency/year)
- 200
- Net saving = 1500 − 200 = 1300 currency/year.
- Payback = 5000 / 1300 years.
- Net annual saving: 1,300 currency/year
- Simple payback: 3.846154 years
2. Comparison example
Compare a different supplied condition using the same method. For Energy Cert Exam, the important check is that the input meaning, units and method assumptions still match the problem.
- Installed cost (currency units)
- 5,000
- Annual energy-cost saving (currency/year)
- 1,000
- Annual maintenance-cost increase (currency/year)
- 200
- Net saving = 1000 − 200 = 800 currency/year.
- Payback = 5000 / 800 years.
- Net annual saving: 800 currency/year
- Simple payback: 6.25 years
Check your understanding
1. Which relationship is used?
Net annual saving = energy-cost saving − maintenance-cost increase; simple payback = installed cost/net saving.
2. Which assumption should you check first?
Tariffs, operating hours and costs are user assumptions. Results exclude financing, taxes, demand charges and changes in equipment performance.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to Certified Energy Auditor (CEA) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.