Yes, CMH are indeed efficient. I remember reading that they convert ~50%+ of their energy into light while for HPS numbers sit at ~27-30%. Considering BTU, doing the math 630W CMH equals the heat produced by 600w HPS+ a miniscule amount of 120 BTU extra.Was your ballast remote or on the fixture? Mines remote so that may be a factor, the HPS ballast was remote as well.
From that link you supplied.
"One watt from a grow light creates four British Thermal Units (BTUs) of heat that need to be cooled. So in comparison, one 600w HPS grow light puts off 2,400 BTU ’s whereas one 315 W CMH grow light puts off only 1,260 BTU’s, which is almost less than half the HPS light. "
"CMH is the best lighting possible for in-home growing. They’re efficient, run cooler than HPS or Double Ended bulbs, and with all the benefits of the new and long-time growers alike can’t go wrong."
*Forgot to add that the ballast was remote.
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