How to calculate lighting energy cost

Annual cost depends on total fixture power, operating hours, days and energy price. The calculator does not forecast tariff changes or driver losses, but it compares variants consistently.

Practical example

A 20 m² room with a 150 lx target needs 3,000 lumens reaching the plane. With UF 0.65 and MF 0.80, the sources need about 5,769 lm. Six 1,000 lm fixtures give an estimated 156 lx.

Limitations

The simplified model does not know fixture intensity curves, individual surface reflectance, obstacles, glare or uniformity. A construction-ready design requires photometric data and suitable software.