Calculation sequence
Step-by-step method
- Subtract confirmed incentives from initial installed cost.
- Subtract added annual maintenance from gross annual savings.
- Divide net initial cost by annual net savings.
CommissioningBeginnerCross-Discipline Energy
Simple Payback Calculator
Calculate simple payback from net initial cost and annual net savings.
Why it matters: Simple payback is easy to communicate but omits time value, escalation, financing, taxes, and savings degradation.
Calculated result
Engineering evaluation
Simple payback period (Y)4.091 years
- Net initial cost (Cn)
- 45,000 $
- Annual net savings (Sn)
- 11,000 $/year
Engineering interpretation
The simple payback is 4.091 years based on $45000 net initial cost and $11000 annual net savings, compared with the entered 5-year maximum. Use life-cycle cost analysis for decisions affected by time value, escalation, financing, taxes, residual value, or savings degradation.
Important limitations
- The status color reflects only the user-entered maximum payback period. SVE Group does not impose a universal payback acceptance threshold.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Cn = I−R
Sn = S−M
Y = Cn/Sn
within entered criterion when Y ≤ Ymax
Current substitution
Cn = 50000−5000 = $45000; Sn = 12000−1000 = $11000/year; Y = 4.091 years.
Equation legend
Inputs and calculated quantities
- I
- Initial installed cost — $
- R
- Incentive or rebate — $
- S
- Annual gross savings — $/year
- M
- Added annual maintenance — $/year
- Ymax
- Entered maximum payback period — years
- Y
- Simple payback period — years
- Cn
- Net initial cost — $
- Sn
- Annual net savings — $/year
Applications
How this calculation is used
Building design
Screen alternatives before life-cycle cost analysis.
Construction
Compare simple change-order cost and annual savings assumptions.
Commissioning
Screen implementation opportunities identified through testing or retro-commissioning.
Quality controls
Assumptions and limitations
Assumptions
- Entered values represent the same stable operating condition.
- Measurements and reference values use consistent units and boundaries.
Limitations
- This is a screening and field-verification tool, not an automatic acceptance decision.
- Project criteria, manufacturer data, governing standards, and measurement uncertainty remain controlling.
Field use
Verification procedure
- Confirm the approved reference values and test boundary.
- Stabilize the system and record calibrated field measurements.
- Review calculation assumptions, uncertainty, and supporting evidence before disposition.
Common engineering mistakes
- Comparing readings taken at different loads, modes, or reference conditions.
- Treating a calculated status as proof of code, contract, or manufacturer compliance.
Technical basis
References and source standards
- U.S. Energy Information Administration—Energy ExplainedFederal reference for energy quantities, use, and cost concepts; users must enter the applicable utility tariff and demand terms.
- U.S. Department of Energy—Industrial Assessment and System ResourcesFederal technical resources for fan, pump, motor, boiler, chiller, and energy-system performance evaluation.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement