HPS & MH Grow Lights

Does HID still make sense?

LED has taken most of the indoor lighting market, and for good reason — but HID has not stopped being useful. It remains the cheapest way to buy a lot of light. A 600W HPS kit costs a fraction of an LED fixture producing comparable output, and the hardware is simple: a ballast, a reflector and a lamp, each replaceable on its own.

Where it costs you is running it. HID draws more power for the same usable light and dumps most of the difference into your grow space as heat, which means more ventilation, more cooling in summer, and a bigger power bill over a full cycle. If your space is cold, that heat is a bonus. If it is a bedroom in February, it is not.

MH, HPS or CMH?

MH is blue-heavy and suits vegetative growth — compact internodes, sturdy stems. HPS is red-heavy and suits flowering, which is why it remains the classic bloom lamp. CMH (also sold as CDM) uses a ceramic arc tube to produce a fuller spectrum including UV, so one lamp does a respectable job of both stages.

The classic HID setup runs MH through veg and swaps the lamp to HPS for flower, reusing the same ballast and reflector — provided the ballast is rated for both.

What a complete kit includes

A kit pairs a ballast with a reflector and usually a lamp. Buying the pieces separately works, but the ballast must be rated for the lamp's wattage and type, and the reflector's socket must match single-ended or double-ended. A kit removes both mismatches.

Heat and ventilation

HID runs hot enough that ventilation is not optional. Size the inline fan for the heat load, not just the tent volume, and consider an air-cooled reflector or cool tube — which lets you duct air directly across the lamp and pull that heat straight out of the space.