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Factory Energy Yield Loss Estimator

The Factory Energy Yield Loss Estimator estimates how much of a production period's energy use is associated with rejected output. It combines total units, good units, total energy consumption, and electricity price to translate yield loss into rejected units, estimated wasted kilowatt-hours, and an indicative energy cost.

This is a proportional allocation model: it assumes each produced unit carries the same average energy burden. That makes it practical for screening and trend analysis, especially when submetering does not isolate the exact energy used by defective units. It should not be treated as a substitute for process-level metering when defects consume materially different amounts of energy than good units.

Inputs

units
units
kWh
$/kWh
Result
—
yield loss
Rejected units—
Allocated energy loss—
Estimated energy cost—

1. Enter total production
Use all units completed or counted during the selected production period.

2. Enter good output
Provide the number of accepted units from the same period.

3. Add total energy use
Enter kilowatt-hours for the same equipment or process boundary.

4. Enter electricity price
Use an average energy price per kWh if you want the cost estimate; enter 0 to focus only on physical energy.

5. Review yield and loss allocation
Use the rejected-unit rate and allocated kWh to prioritize periods for deeper root-cause analysis.

Rejected units = Total units - Good units Yield loss % = Rejected units / Total units × 100 Average energy per unit = Total energy / Total units Allocated energy loss = Rejected units × Average energy per unit Estimated energy cost = Allocated energy loss × Energy price

Total units — all units produced in the period

Good units — accepted units

Total energy — kWh consumed by the measured boundary

Energy price — currency cost per kWh

Assumptions: Energy is allocated evenly across total units. Actual defect-related energy can differ if rejects occur early or late in the process.

What the result means

The yield-loss percentage shows the share of produced units rejected, while the energy figures estimate the energy burden attributable to that rejected share.

Treat allocated energy loss as an estimate unless the defect pathway is directly submetered.

Given

  • Total units: 10,000
  • Good units: 9,650
  • Energy use: 4,200 kWh
  • Energy price: $0.14/kWh

Calculation

Rejected units = 10,000 - 9,650 = 350

Yield loss = 350 / 10,000 × 100 = 3.50%

Average energy per unit = 4,200 / 10,000 = 0.42 kWh

Allocated energy loss = 350 × 0.42 = 147 kWh

Estimated cost = 147 × $0.14 = $20.58

Result
3.50% yield loss

Interpretation
Under the proportional allocation assumption, the rejected share corresponds to about 147 kWh and $20.58 of energy cost for the period.

Is allocated energy loss the exact energy wasted on defects?

Not necessarily. It is an average allocation based on the rejected share of output. Defects found early in the process may consume less energy than average, while late-stage defects may consume more.

Can good units be zero?

Yes. A period with zero good units produces a 100% yield loss as long as total units are greater than zero.

Should reworked units count as good or rejected?

Use the classification that matches your quality reporting system. If reworked units ultimately become saleable, you may want to track rework energy separately rather than treating them as simple rejects.

What if my electricity price changes during the period?

Use a weighted average price for the same period, or enter 0 and calculate cost separately from more detailed tariff data.

How is this different from overall equipment effectiveness?

Yield loss focuses on the quality share of production and its estimated energy burden. OEE combines availability, performance, and quality into a broader production-effectiveness measure.