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.Continue Reading
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.
The data points should then be inserted into the formula: Watts = lumens / luminous efficacy.
Divide 1500 lumens by the luminous efficacy figure of the light in question with a calculator to determine the answer in this case.