# Confused about HPS watts versus lumen ratio



## SensiStarFan (Mar 15, 2011)

Hi all!  

So a 400 watt HPS will put oout 45,000 lumens. A 600 watt HPS puts out 95,000 lumens. And a 1,000 watt HPS puts out 145,000 lumens. 

This means a 400 watt HPS produces 112 lumens per watt. A 600 watt HPS produces 158 lumens per watt. And a 1,000 watt HPS produces 145 lumens per watt. 

So I have two questions. First, did I leave something out in this consideration or is a 600HPS in fact more efficient than either a 400 or a 1,000? Secondly and probably more difficult, can anyone tell me exactly why the efficiency is different for different watt ballasts?

-SSF-


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## The Hemp Goddess (Mar 15, 2011)

I do not know why the efficiency of the lights differs.  However, you are correct that the 600W is the most efficient.


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## OGKushman (Mar 15, 2011)

E= output over input. Efficiency is dependant upon internal friction of the system. In this case heat added per watt drawn. 

The formula would take a long time to determine the variables. But basically the 600 watt system is easier to cool per lumen/per watt. This means less energy is lost to heat transfer


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