Ceramic Metal Halide (CMH) Lights

A ceramic metal halide grow light covers blue, red and some UV from a single 315W lamp that draws about 340W at the wall. Pick 4000 to 4200K lamps for veg, 3000 to 3200K for flower, or mix both for a full-cycle room.

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Ceramic Metal Halide (CMH) Lights

Ceramic Metal Halide Grow Light Systems: CMH Lamps, Fixtures and Ballasts

A ceramic metal halide grow light runs its arc inside a ceramic tube instead of quartz, so it holds a hotter, steadier arc. That gives a broad, daylight-like spectrum with a CRI of 80 to 95 or higher. Picking a lamp? Start with our test of the best 315W CMH bulb for flowering....

Ceramic metal halide grow light infographic: CMH lamps, fixtures and ballasts, color temperatures, coverage and lamp life

CMH sits between classic HID and LED in our grow lights lineup. Running 630W or double-ended units? Those live in Double Ended + CMH Fixtures.

Types of CMH Grow Lights

CMH Lamps

SunPulse 3200K posted the top PAR among lamps we still carry in our ten-lamp test. Growers Choice 3100K follows at 565 µmol/s. Ushio HiLux Gro 4200K has the highest CRI, above 95, which suits veg rooms. GrowLite adds 4000K single-ended and double-ended 315W options.

Complete CMH Fixtures

The DLI CRI-Series 315W runs at 1.7 µmol/W in a low-profile housing for tight ceilings. Endomaxx 150 and 315 luminaires are rated for greenhouses and wet locations. The Solis Tek C1 and ILUMINAR 315W round out the range, and the ILUMINAR ships without a lamp.

CMH Ballasts and Kits

CMH lamps need a matched ballast, usually low-frequency square wave. The PLS 315W remote ballast and GrowLite 315W electronic ballast keep that heat outside the room. The AllState 945W DigiLamp kit pairs a double-ended lamp with a 240V EnergyStation ballast.

How Growers Use CMH Lighting

A 315W fixture fits tents, small rooms and greenhouse benches. Run 4000 to 4200K lamps through veg and 3000 to 3200K through flower. Ceramic lamps emit some UV, so wear UV-rated glasses when working under them.

Frequently Asked Questions

What is a CMH grow light?

It is a metal halide lamp with a ceramic arc tube in place of quartz. The ceramic handles more heat, giving steadier color and a CRI of roughly 80 to 96. CDM is Philips' original name for it, and LEC is one brand's trademark.

CMH vs HPS?

HPS gives a narrow orange-red spectrum at higher wattages, while CMH spreads output across blue, red and some UV. A 315W CMH draws about 340W, so it adds less heat per fixture than a 600W HPS. Many growers flower under 3100K CMH.

CMH bulb for flowering or veg?

Use 3000 to 3200K for flowering and 4000 to 4200K for veg. In our 315W lamp test, every top-three PAR result came from a warm 3000 to 3200K lamp. The 4200K lamps render color better, which helps in veg rooms and when scouting for pests.

315W CMH coverage?

Plan on about 12 square feet per 315W fixture. Endomaxx rates its 315 at 12 square feet from 30 inches above the canopy, roughly a 3.5 by 3.5 foot area. For a 4x4 or larger space, run two 315W fixtures or step up to a double-ended CMH setup.

How long do CMH bulbs last?

Rated life runs from 10,000 to 30,000 hours, depending on the lamp. Growers Choice rates its 315W lamps at 10,000 hours, Ushio HiLux Gro at 15,000, SunPulse at 20,000 and Endomaxx at 30,000. Output fades before a lamp fails, so many growers replace on a set schedule.