315W LEC/CMH Cannabis Grow Setup & Tutorial

Updated Jan 24, 2021

by Nebula Haze

Example setup with a 315 LEC grow light (also known as a CMH grow light)

See More Growing Setups


315W LEC Grow Setup (For Hobbyist Growers)

  • Average Yields: 5-10 ounces (we’ve harvested as much as 17 ounces, learn how)
  • Recommended 2-8 plants
  • Grow space: at least 2×4’ or 3’x3′ with a height of 5′ or more


About This Setup

The 315W LEC grow light (a brand name version of the “Ceramic Metal Halide”) is relatively new to the growing scene and is a popular alternative to HID lighting. It excels in the vegetative stage where it produces fast growth, though it also does a great job in flowering by producing strong, sparkly bud. LECs provide a significant amount of UV-A which may explain why the buds tend to look so glittery.

Pros: One bulb for the entire grow, great results, non-suspicious colored lighting, great for SOG

Cons: Needs significant height above plants, the LEC itself is pricey by comparison to HIDs

Learn more about growing cannabis with LECs


Cost Estimates

  • Total Setup Cost: $940 + Cost of Seeds
  • Estimated Electricity Cost: $29-58/month (based on $0.12/kWH to $0.25/kWh – see breakdown)
  • Total Cost for Entire First 4-Month Grow (Setup + Electricity): $1056-$1172 ($106-235/ounce based on average yield of 5-10 ounces)
  • Total Cost for Second Grow (Nutrients + Electricity): Up to $332 ($33-67/ounce based on average yields)
  • If you follow these 8 simple steps you can harvest a pound (16 oz) or more with this system, bringing the per-ounce cost as low as $20/ounce after the first grow.

View a full growing tutorial using LEC grow lights


Complete Grow Supply List

This cannabis grow room setup list includes all the supplies you need to get to harvest.

Grow Light

315 LEC Grow Light

  • The model I use and recommend is this 315 LEC Grow Light from Sun System. It comes with a Philips 4200K colored bulb.
  • (optional) Get a 3100k Philips 315 LEC bulb for the flowering stage. It increases yields to an extent but buds tend to come out less sparkly. I personally use the 4100k version from seed to harvest.
  • Cost: ~$420 (the price fluctuates on Amazon so if it’s higher try shopping around)

Get an LEC grow light for growing cannabis on Amazon.com
Sun System 315W LEC Grow Light

Grow Space

Learn more about choosing and setting up an exhaust fan.

Plant Pots


  • You need a “vegetative” or all-purpose plant nutrient for the first part of your plant’s life
  • You need a “bloom” or low-nitrogen nutrient for the budding phase
  • Many nutrient systems have a nutrient schedule so you give your plants the right ratios for each stage of life
  • Always start at half strength with a new base nutrient system because the recommended strength is typically too high for cannabis
  • Get examples of great cannabis nutrients
  • Recommended Base Nutrients: General Hydroponics Flora trio (use at half strength) + CaliMagic (use at full strength)
  • (Optional) Bloom Supplement: General Hydroponics Floralicious Bloom
  • Cost: $50-100

General Hydroponics Flora trio - includes all your base nutrients! General Hydroponics CaliMagic Cal-Mag supplement
General Hydroponics Flora Trio and CaliMagic

Other Supplementary Items

Learn about other cool growing tools

Estimated Cost: $940 plus the cost of seeds

See Additional Grow Setups

Cannabis plants in the vegetative stage under a 315 CMH grow lightCannabis plants growing under a 315 LEC Grow Light


Cannabis plants under a 315 LEC grow light in 2-gallon smart pots

CMH grow lights produce extremely fast and healthy vegetative growth. These plants are only 29 days old.


Cannabis plants growing under a 315 CMH grow light (not long before harvest)

Cannabis plants flowering under a 315 LEC Grow Light


LEC grow lights over maturing cannabis plants; plants can be seen in reflector as well

A 315 LEC (CMH) Grow Light Fixture by Sun System


Cannabis cola grown from seed to harvest under a 315 LEC grow lightExample of buds grown under a 315 LEC grow light from seed to harvest in this setup (pictured above and below)


Example of a marijuana cola that was grown under a 315 CMH grow light



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