How Much Light Do I Need

Light sources

Luminous flux is measured in lumens (lm) and indicates how much light is emitted by a light source. Power usage is measured in watts and was previously used as a standard for the quantity of light emitted by a light source. Since the filament light sources have been prohibited in many countries the use of watt as an expression for light intensity is no longer advisable because new luminaire technologies are far more effective than the traditional filament bulb which probably made 10% light only out of the total energy input; the remaining energy disappears as heat. Light sources can in general no longer be directly compared to other types because luminous efficacy varies greatly between the various types of light sources.

Here is a brief overview of power usage in watts (W) and luminous efficacy in lumens (lm) of various luminaries.

The efficacy (output) of luminaires is measured in lumens per watt and is eventually a better expression for how much light you get out of the energy you put into a light source.

Shortly expressed; energy-saving bulbs have 5-6 times more luminous efficacy per watt, and LED bulbs 7-8 times, compared to conventional filament bulbs.

How much lumen do I need for each room?

A simple overview of approximately how much light is in demand in the various rooms throughout a home.

Keep in mind, these are very rough estimates and account for having different types of bulbs and lighting options in each room. Size, materials and colours in a room influence the perception of how much and how little light is needed and the ability to adjust the output of light is a perfect way to find the right amount of lumens for a specific space and specific event that will personalize lighting.

Carsten Joergensen October 27, 2019