400W MH/HPS Cannabis Grow Setup & Tutorial

Updated Jan 24, 2021

by Nebula Haze

What 400W HPS grow lights look like in action

See More Growing Setups


400W HPS Grow Setup (For Hobbyist Growers)

  • Average Yields: 7-14 ounces
  • Recommended 2-6 plants
  • Grow space is 3’x3’x6′ or 4’x4’x6′ (bare minimum is 2’x4’x6′)


About This Setup

When you’re just starting to foray into the world of larger grow lights, a 400W HPS is an appropriate first light to try. It’s energy efficient, relatively cheap, and makes for large colas than stretch far down the plant. These light are more popular than the 250W HPS, but less than the 600W HPS, and far less popular than the current line of LEDs or LECs. Still, these lights are a workhorse and will pay for themselves quickly in any medium-sized indoor cannabis grow.

Pros: Cheap, effective, high yields and potency

Cons: Not popular, yellow spectrum is easy to spot by nosy people, some models emit RFI which can alert HAM radio users to your grow


Cost Estimates

  • Total Setup Cost: $744.00
  • Estimated Electricity Cost: $46-96/month (based on $0.12/kWH to $0.25/kWh – see breakdown)
  • Total Cost for Entire First 4-Month Grow (Setup + Electricity): $1128 ($81-161/ounce)
  • Total Cost for Second Grow (Nutrients + Electricity): $414 ($30-59/ounce)

Check Out More Examples of Grow Setups


Complete Grow Supply List

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

Grow Light

* Alternative LED Grow Light: HLG 300 R-Spec LED Grow Light (better option if heat is a concern, runs much cooler!)

A 250W/400W switchable HPS light by Sun Systems
Sun System Digital 400 Complete – Get a 400W MH bulb and 400W HPS bulb with this setup

Grow Space

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

Estimated Cost: $744 plus the cost of seeds

See Additional Grow Setups

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