So much misinformation in this thread. Its about efficiency and photons per watt a 630 cmh is 2 315 bulbs in the same hood. The 315 cmh has a much higher efficiency than de hps. The more efficient the more photons are being produced and the less heat there is.
315 cmh is about 10% more efficient than a de hps. De's are 40% efficient. The 315 cmh is producing more photons per watt than the de.
The Philips 315W Bulb it the most efficient with the highest output I would agree that, But taking cost into consideration for the right 315W LEC/CMH Light fixture with the Philips bulb lets say from ''Sunlight Supply'', AGAINST the DE 630W LEC/CMH,
The cost of two 315W LEC/CMH Fixtures From Sunlight supply would cost you around $1,200,
The cost of a DE 630W LEC/CMH Fixture would cost you between $550 to $600,
They both give off less heat than a HPS and the output and spectrum between two Philips bulbs against a DE 630W Bulb are not a million miles apart, Some people would put 2 x Sunlight Supply 315w fixtures in a 3' x 6', and some people would put 2 x DE 630W in a 4' x 8', What's more efficient for cost per yield? I think you would yield a lot more with two DE 630W LEC Fixtures in a 4' x 8' for the same investment as two 315W Sunlight supply Fixtures in a 3' x 6'.
I think the DE LEC/CMH are more efficient on cost because two DE 1000W LEC/CMH Fixtures are the same price or maybe just a little bit more as two 315W Sunlight supply fixtures, And what is going to yield more two 315w fixtures from sunlight supply in a 3' x 6' or two DE 1000W Fixtures in a 5' x 10'. Its got to be a no brainer!