Transformer Efficiency Operating-Cost Comparator — Compare Losses at Real Loading
Compare two transformers using no-load loss and load-dependent loss at your actual operating point. See annual losses, annual electricity cost and the difference between options.
Common operating conditions
Transformer A
Transformer B
Why transformer operating cost depends on loading
Transformer losses have two useful categories for a planning comparison: no-load loss while energized and load-dependent loss that changes with current and therefore approximately with the square of loading under this simplified model.
Why the rating matters
The same absolute load can produce different loss levels on two transformers with different ratings because the per-unit loading changes.
Why no-load loss is included
A transformer can consume core-loss energy even when useful load is low. This matters for continuously energized equipment.
Worked example
At 700 kVA on a 1,000 kVA transformer, the load fraction is 70%. A 12 kW rated load-loss value becomes 12 × 0.7² = 5.88 kW under this model.
Limitations
Real transformer performance can depend on temperature, harmonic loading, voltage, cooling mode and detailed manufacturer characteristics.
Frequently asked questions
Should load loss be entered at full rated load?
Yes for this model. The calculator then scales it by loading squared.
Does the tool calculate full transformer efficiency?
It derives loss and energy cost from the entered operating point rather than relying only on a headline efficiency figure.
Can energized hours be lower than 8,760?
Yes. Use the actual annual energized schedule.