Calculation sequence
Step-by-step method
- Calculate baseline and proposed annual energy.
- Multiply each by the entered blended energy rate.
- Subtract proposed energy-only cost from baseline energy-only cost.
CommissioningBeginnerEnergy
Operating-Cost Comparison Calculator
Compare baseline and proposed electricity cost from input power, annual hours, and energy rate.
Why it matters: A transparent operating-cost screen helps prioritize improvements without implying a life-cycle analysis.
Calculated result
Engineering evaluation
Estimated blended-energy cost savings (Sav)9,600 currency/year (energy only)
- Baseline energy (Eb)
- 400,000 kWh/year
- Proposed energy (Ep)
- 320,000 kWh/year
- Baseline energy-only cost (Cb)
- 48,000 currency/year
- Proposed energy-only cost (Cp)
- 38,400 currency/year
Engineering interpretation
The entered blended energy-rate comparison yields estimated annual energy-only savings of 9600 currency units.
Important limitations
- Demand charges, ratchets, time-of-use rates, taxes, maintenance, escalation, interactions, persistence, and capital cost are excluded.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Eb = Pb·t
Ep = Pp·t
Cb = Eb·R
Cp = Ep·R
Sav = Cb−Cp
Current substitution
Eb = 100×4000 = 400000; Ep = 80×4000 = 320000; Sav = 48000−38400 = 9600.
Equation legend
Inputs and calculated quantities
- Pb
- Baseline input power — kW
- Pp
- Proposed input power — kW
- t
- Annual operating hours — h/year
- R
- Blended energy rate — currency/kWh
- Sav
- Estimated blended-energy cost savings — currency/year (energy only)
- Eb
- Baseline energy — kWh/year
- Ep
- Proposed energy — kWh/year
- Cb
- Baseline energy-only cost — currency/year
- Cp
- Proposed energy-only cost — currency/year
Applications
How this calculation is used
Building design
Compare operating alternatives.
Construction
Check metering and sequence assumptions.
Commissioning
Estimate annual energy and cost difference from field power data.
Quality controls
Assumptions and limitations
Assumptions
- Entered data describe one stable operating condition and use consistent measurement boundaries.
- Time, energy, and performance values are representative of the stated interval.
Limitations
- This is a preliminary evaluation and commissioning-support tool, not an automatic acceptance determination.
- Project sequences, manufacturer data, tariffs, codes, and professional review remain controlling.
Field use
Verification procedure
- Confirm the operating mode, test boundary, and instrument calibration.
- Collect simultaneous readings or a documented trend interval.
- Compare the result with the approved sequence, submittal, and project criteria.
Common engineering mistakes
- Combining measurements from different operating modes or time intervals.
- Ignoring sensor uncertainty, trend sampling, or the defined equipment boundary.
Technical basis
References and source standards
- U.S. Department of Energy—Better Buildings Solution CenterFederal HVAC energy-management and equipment-performance guidance.
- NIST Measurement and Calibration ResourcesFederal measurement, calibration, timing, and unit-system context.
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