To convert 1500 lumens to watts, first determine the luminous efficacy of the electric light source. Then take the number of lumens and divide this by the figure for luminous efficacy.
- Determine the luminous efficacy of the light source
Each light source (LEDs, halogen lamps, etc.) has a fixed luminous efficacy. Identify the kind of electric light used, and then find the luminous efficacy using a table.
- Insert figures into the formula
The data points should then be inserted into the formula: Watts = lumens / luminous efficacy.
- Complete the calculation
Divide 1500 lumens by the luminous efficacy figure of the light in question with a calculator to determine the answer in this case.