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I have 80 watts of CFL and a 250HPS in the middle.
My closet is 29" by 41". Luckily the ceiling is high up, about 4 meters, even so, I have to have the door open, fans, and let cold air into the apartment regularly. If I closed the door, I would reach 40c probably within an hour.

Interestingly, the 4 * 23w cfl's seem to raise the temp by about one degree centigrade each, so even those ones added another 4c.

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faithless Reviewed by faithless on . heat differences: 250w or 400w HPS? A friend of mine is starting a small closet grow in which the ventilation issues could be a problem. ventilation will be somewhat limited, so heat is a concern. He is about to purchase a light, but is unsure which one. He is sure of a HPS system, but wondered if 250 or 400 would be better. Its a small closet so he will still have plenty of lumens with a 250w, but 400 is obviously better. Our question is, how much of a heat difference will there be between the two bulbs? Is the 400 much Rating: 5