Lighting
Lighting Wall-Plug Efficiency Calculator
The purpose of Lighting Wall-Plug Efficiency is to turn visible optical power and electrical input power into wall-plug efficiency. Keep the source condition with the saved result so later comparisons remain meaningful.
Set up the Lighting Wall-Plug Efficiency case
Enter ratings or measurements that describe one scenario.
Formula used on this page
This page evaluates efficiency = optical ÷ electrical × 100. The participating entries are Visible optical power and Electrical input power.
The defaults produce 28.00%. Replace them with measurements from one operating state.
Calculate wall-plug efficiency from visible optical power and electrical input power. A separate daylight factor result is available from Daylight Factor Calculator.
Input notes
Keep lumens, candela, lux, and foot-candles on the correct geometric basis. If operating conditions changed between readings, calculate separate cases.
At least one field has a positive lower bound because it appears in a denominator. Check every prefix before entry; micro, milli, kilo, and mega are not interchangeable. If you also need round-trip efficiency, continue with Battery Round-Trip Efficiency Calculator.
- Visible optical power
- Default example: 28 W. Enter visible optical power in W.
- Electrical input power
- Default example: 100 W. Enter electrical input power in W.
What the number means
Read Wall-plug efficiency as the outcome of this equation, not as automatic equipment approval. Compare it with illuminance, uniformity, driver loading, voltage loss, energy use, and maintained output.
Label alternate cases rather than overwriting the baseline. For the companion motor efficiency calculation, open Motor Efficiency Calculator.
Where this estimate can fail
This is not the same as luminous efficacy.
The arithmetic intentionally leaves out driver efficiency, optical loss, surface reflectance, and beam-edge definition. Document which effects were checked elsewhere in the analysis.
Keep lumens, candela, lux, and foot-candles on the correct geometric basis.
A second scenario
Change Visible optical power from 28 W to 33.6 W and preserve the rest of the case. This moves the answer from 28.00% to 33.60%.
Use a separate scenario when multiple conditions change together.
Documenting the calculation
Document visible optical power and electrical input power with wall-plug efficiency. Keep enough context to reproduce the result later.
Carry wall-plug efficiency unchanged when passing it to the next worksheet. Apply standard sizes only after all checks are complete.
Review the case step by step
Review visible optical power and the remaining entries as one case. If one value belongs to another temperature, load, or time period, separate the scenarios.
The displayed wall-plug efficiency should be checked against illuminance, uniformity, driver loading, voltage loss, energy use, and maintained output. Investigate an unexpected magnitude before changing the model or adding margin.
If uncertainty remains, calculate labeled low and high cases. Include fixture distribution, reflections, mounting, maintenance, and meter position when those effects can change the decision.