HPS & MH Grow Lights

Why HID still has a place

LED now takes most of the indoor lighting market, and that is fair enough — HID is useful all the same. It is still the cheapest way to buy a lot of light. A 600W HPS kit costs a fraction of an LED fixture that produces comparable output, and the hardware stays simple: a ballast, a reflector and a lamp, each replaceable on its own.

The cost shows up when you run it. HID draws more power for the same usable light and dumps most of that extra draw into the grow space as heat. That means more ventilation, more cooling in summer, and a bigger power bill over a full cycle. A cold room can use that heat. A bedroom in February cannot.

MH, HPS and CMH

MH leans blue, which is what vegetative growth wants — short internodes and sturdy stems. HPS leans red, which is what flowering wants, and that is why it is still the classic bloom lamp. CMH (also sold as CDM) uses a ceramic arc tube. The result is a fuller spectrum, UV included, so a single lamp can cover both stages reasonably well.

Growers who stay on HID often veg under MH, then swap the lamp to HPS for bloom and keep the same ballast and reflector — so long as that ballast is rated for both.

What comes in a complete kit

A complete kit puts a ballast and a reflector together, and usually includes a lamp. You can still buy the parts one by one. What you cannot skip is the pairing: ballast wattage and type have to match the lamp, and the reflector socket has to match single-ended or double-ended. The kit is how you avoid getting either of those wrong.

Heat, exhaust and ventilation

You cannot treat ventilation as optional on HID — these lamps run hot. Size the inline fan for the heat load rather than tent volume alone, and look at an air-cooled reflector or a cool tube so you can duct air across the lamp and send that heat straight out of the room.