Hydroponic Lights

Choosing between LED, HPS and CMH

LED is the default pick for most new rooms. It stays cooler, it draws less power for the same output, and bar-style fixtures wash the canopy evenly instead of punching a single hot spot. The trade-off is the purchase price — that cost sits at the front.

HPS is still a common flowering lamp. The kit is cheap to buy, the spectrum leans red where bloom plants work, and a 600W or 1000W bulb throws a lot of light for the money. It also runs hot, which is a problem in summer and an advantage in a cold shed.

CMH (also sold as CDM) sits between those two — a fuller spectrum than HPS, better efficiency than MH, and a light quality growers often prefer in veg. MH is the traditional veg lamp, still run where a full HID setup is already in place.

How much light do you need?

Start from the tent footprint, not the plant count. As a rough guide, growers allow about 30–50W of modern LED per square foot of canopy, or 400–600W of HID for a 1.2 x 1.2m tent. Coverage is as important as the wattage on the box: a fixture rated for a smaller footprint leaves dim corners that extra power will not fill.

Check the numbers on the Grow Light Electricity Calculator before you buy — over a full cycle the running cost often outweighs the gap in purchase price between two fixtures.

What else the light needs

HID lamps need a ballast matched to wattage and type, and a hood or reflector to send the light down. LEDs usually arrive self-contained and still need hanging. Every fixture needs a timer — do not run the light cycle by hand — and HID heat means the ventilation has to keep up.

Light for each stage

Seedlings and cuttings want very little. A propagation light, T5 or CFL is enough, and stronger light can stall them. Veg suits a full-spectrum LED or CMH. Flower is where the heavy fixtures earn their keep, and where growers add under-canopy bars to reach the lower sites a top fixture cannot.