Luminous efficacy (luminous efficiency) defines the ratio of the luminous flux emitted by a specific light source to the energy consumed by it per unit time.
Examples of luminous efficiencies of various light sources:
- bulb: 8-10 lm / W
- halogen lamp: 16 lm / W
- fluorescent lamp: 45-104 lm / W
- white LED: 26-100lm / W
- metal halide lamp: 85-115 lm / W
- high pressure sodium lamp: 150 lm / W
- low pressure sodium lamp: 200 lm / W