Transformer losses calculator
Estimate transformer no-load, load and annual energy losses from entered loss data, load percentage, operating hours and energy rate for Australian project records.
Pload_loss = Pfull_load_loss x (load_% / 100)^2; Ptotal_loss = Pno_load_loss + Pload_loss; Eannual_loss = Ptotal_loss x operating_hours; Cost = Eannual_loss x energy_rate- No-load loss is treated as constant for the entered operating period.
- Load loss scales with the square of the entered load percentage.
- Operating hours and energy rate are entered project assumptions.
- The review limit is an entered annual kWh comparison value, not a supplied threshold.
| Variable | Meaning | Unit | Use |
|---|---|---|---|
| Pno_load_loss | No-load loss | kW | Entered constant transformer loss. |
| Pfull_load_loss | Full-load loss | kW | Entered full-load winding or load-loss value. |
| load_% | Load percentage | % | Entered load as a percentage of transformer rating. |
| Pload_loss | Load loss at condition | kW | Full-load loss scaled by load fraction squared. |
| Ptotal_loss | Total loss | kW | No-load loss plus load loss at the entered condition. |
| operating_hours | Operating hours | h/year | Entered annual operating period. |
| Eannual_loss | Annual loss energy | kWh/year | Total loss multiplied by annual operating hours. |
| Cost | Annual loss cost | AUD/year | Annual loss energy multiplied by entered energy rate. |
| Limit | Review limit | kWh/year | Optional entered annual loss comparison value. |
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Transformer losses calculator technical guide
Estimate transformer no-load, load and annual energy losses from entered loss data, load percentage, operating hours and energy rate for Australian project records.
Use this page when a transformer schedule or energy review needs a transparent loss worksheet. Enter no-load loss, full-load loss, the reviewed load percentage, annual operating hours and an optional energy rate to estimate annual loss energy and cost context.
The output is a worksheet record. It does not choose a transformer, decide efficiency class, compare product performance data, set duty conditions or replace manufacturer data.
Loss Use Cases
| Work setting | Real question | Useful action from this page |
|---|---|---|
| Existing transformer review | How much annual loss energy follows from the entered duty? | Enter no-load loss, full-load loss, load percentage and operating hours. |
| Replacement discussion | Which loss number should be carried into an energy review? | Create a traceable record before comparing product data outside the calculator. |
| Part-time transformer | How does limited operating time affect annual loss energy? | Enter the annual hours for the actual duty rather than assuming a full year. |
| Project comparison | Does the annual loss estimate sit above an entered review value? | Enter an annual kWh review limit and read the margin as a project comparison. |
Loss Boundary
No-load loss and full-load loss must come from a transformer source. The calculator does not supply product tables or decide whether one transformer is better than another. It records the arithmetic for one entered basis so the loss data, operating hours and energy rate can be reviewed together.
The load percentage should describe the condition being reviewed. A load profile, duty cycle, temperature condition, ventilation issue, tariff basis or product-specific efficiency condition can change the real project decision outside this worksheet.
Formula Basis
The load fraction is:
text load_fraction = load_% / 100
The load loss at the entered condition is:
text Pload_loss = Pfull_load_loss x load_fraction^2
The total loss, annual energy and cost context are:
text Ptotal_loss = Pno_load_loss + Pload_loss Eannual_loss = Ptotal_loss x operating_hours Cost = Eannual_loss x energy_rate
Review Workflow
- Confirm that the no-load and full-load loss values belong to the transformer being reviewed.
- Enter the load percentage for the operating condition being studied.
- Enter annual operating hours from the duty or project record.
- Add an energy rate only when cost context is useful.
- Add an annual loss review limit only when the project has a comparison value.
- Keep the result with the product data, tariff basis and operating-duty notes.
Worked Records
| Situation | Inputs | Result | Example project entry |
|---|---|---|---|
| Distribution transformer | 500 kVA, 65% load, 0.85 kW no-load loss, 5.4 kW full-load loss, 8760 h/year | 27,431.94 kWh/year and $8,778.22/year at 32 c/kWh | "TX-LOSS-1 loss record is below the entered 30,000 kWh/year review value." |
| Higher loss review | 315 kVA, 100% load, 2 kW no-load loss, 20 kW full-load loss, 8760 h/year | 192,720 kWh/year and negative margin against the entered 10,000 kWh/year review value | "TX-LOSS-2 needs transformer data and duty-basis review before handoff." |
| Part-time transformer | 50 kVA, 40% load, 0.12 kW no-load loss, 0.75 kW full-load loss, 3000 h/year | Loss-energy record without an entered annual limit | "TX-LOSS-3 records annual loss for part-time operation; no comparison limit entered." |
Boundary With Related Calculations
| Related task | Use this page? | Why |
|---|---|---|
| Transformer current and kVA | Not directly | Use current and kVA when the question is rating, primary current or secondary current. |
| Transformer sizing | Sometimes before this page | Use the sizing worksheet when required kVA is still being established. |
| Voltage regulation | No | Regulation uses transformer impedance and power factor, not loss data. |
| Energy cost | Sometimes after this page | Use energy cost for broader tariff or running-cost context. |
| Product efficiency comparison | No | Compare products only with complete product data and the same duty basis. |
Distribution transformer loss record
A 500 kVA transformer has entered no-load and full-load loss values and the reviewer wants an annual loss record.
- Transformer reference
- TX-LOSS-1
- Rating
- 500 kVA
- Load
- 65%
- No-load loss
- 0.85 kW
- Full-load loss
- 5.4 kW
- Operating hours
- 8760 h/year
- Load loss2.282 kW
- Total loss3.132 kW
- Annual loss27431.94 kWh/year
- Annual cost context$8778.22/year
Carry the result forward with the transformer loss and duty basis.
The annual loss estimate is below the entered annual loss limit, with the tariff and duty basis kept visible for review.
- No-load and full-load loss values are entered from a transformer source.
- The load percentage represents the reviewed duty point.
- The energy rate is an entered comparison value.
Higher loss review record
A high-loss operating case is compared with an entered annual energy limit for project review.
- Transformer reference
- TX-LOSS-2
- Rating
- 315 kVA
- Load
- 100%
- No-load loss
- 2 kW
- Full-load loss
- 20 kW
- Operating hours
- 8760 h/year
- Load loss20 kW
- Total loss22 kW
- Annual loss192720 kWh/year
- Annual cost context$57816/year
The annual loss estimate is above the entered project review limit.
The annual loss estimate is above the entered limit, so the transformer data and operating-duty basis need review.
- The full-load loss value is entered by the user.
- The review limit is a project comparison value.
- The worksheet does not decide product suitability.
Part-time control transformer
A smaller transformer operates for a defined annual period and needs a loss-energy record without a comparison limit.
- Transformer reference
- TX-LOSS-3
- Rating
- 50 kVA
- Load
- 40%
- No-load loss
- 0.12 kW
- Full-load loss
- 0.75 kW
- Operating hours
- 3000 h/year
- Load loss0.12 kW
- Total loss0.24 kW
- Annual loss720 kWh/year
- Annual cost context$201.6/year
Carry the result forward with the transformer loss and duty basis.
The result is a loss-energy record only because no annual review limit was entered.
- The transformer does not operate all year.
- The entered energy rate is used only for cost context.
- Manufacturer data and duty review remain separate.