syde00 ~ Makes sense to me. Unfortunately, physics and themodynamics are nowhere near my stong suit. My youngest son is an expert in those fields but, I can't exactly approach him on the subject.:jointsmile:

What you and shake have said is starting to make sense to me. So, if I've got this correct; the more efficient the lamp is at converting electricity to light, i.e. more lumens per watt, then the less heat it should generate.

So, if a standard 250 watt MH bulb puts out 20,000 lumens

and a standard 250 watt HPS bulb puts out 28,500 lumens

with a Hortilux 250 watt HPS bulb is putting out 30,500 lumens

then both HPS's would generate less heat than the MH and the Hortilux would run slightly cooler than the standard HPS bulb.

Oh no. My brain is starting to feel like it did after reading all the lengthy threads on building the perfect LED lamps. Just kidding. No offense what-so-ever meant to the participants in those discussions. It just got a bit over my head.:wtf: OK. Way over my head.