Which grow light is right for you?

Sorting fact from fiction in the world of HID, CMH, LED and more.

When it comes to indoor growing, your hydroponics lighting setup is one of the most important decisions you’ll make. Whether you're propagating seedlings, keeping leafy greens ticking over, or chasing big yields in flowering crops, the type of light you use directly affects plant health, growth speed, and your energy use.

With all the acronyms out there, it can get confusing - so here’s a practical guide to what each option offers, and when to use it.

 

🔴 HID (High Intensity Discharge) - HPS + MH

This is the old faithful for many growers - a tried and tested technology that’s still one of the most popular here at Ōtaki Hydro. HID setups run two types of bulbs:

• HPS (High Pressure Sodium): intense red-orange light, great for flowering
  

• MH (Metal Halide): stronger in the blue spectrum, used for vegetative growth
  

Most people stick with HPS for the full grow cycle, but those wanting more control will run MH during veg, then switch to HPS for flowering. Both bulbs can be used in the same fixture.

Pros:

• Proven results, high output
• Lower upfront cost
• Easy to switch between bulbs
  

Cons:

• Runs hot — needs solid ventilation
• High power consumption (about 90% of energy goes to heat)
• Bulbs need replacing more often
  

Best for: Growers with larger, well-ventilated spaces who want a reliable, budget-friendly option with strong flowering performance.

🌞 CMH (Ceramic Metal Halide)

CMH is a more modern take on HID — it’s a different fixture, so you’ll need dedicated gear, but it brings some clear benefits. CMH offers a full-spectrum light that mimics sunlight, including UV and infrared, which can help reduce pests and support healthier plants overall.

It produces less heat than HID and is more efficient, meaning you’ll get more usable light per watt. Bulbs also last longer.

Pros:

• More efficient than HID
• Lower heat output
• Excellent full-spectrum light
• Longer bulb lifespan
• Lower ongoing operating costs than HID lights.
  

Cons:

• Higher upfront cost
• Requires its own specific fixture
  

Best for: Full-cycle grows, large plants, and growers wanting a more natural spectrum without jumping straight to LED.

💡 LED (Light Emitting Diode)

LEDs have come a long way. Today’s systems are full-spectrum, long-lasting, and super efficient — turning almost all their energy into usable light with very little heat output. Some allow you to dim or shift spectrum depending on the stage of your grow.

They cost more upfront but pay off in the long run with lower energy use and fewer replacements.

Pros:

• Very low heat
• Long lifespan (50,000+ hours)
• Adjustable spectrum and dimming options
• Great for small spaces or stealth grows
  

Cons:

• Higher initial investment
• Lower intensity compared to HID or CMH
  

Best for: Low-maintenance setups, small-to-medium spaces, or anyone wanting a long-term, efficient grow solution.

🌱 CFL (Compact Fluorescent Light)

CFLs are a simple, cheap option for beginners or very small grows. They don’t get hot and are easy to set up, but they lack intensity and aren’t suitable for flowering or full-cycle growing.

In practice, CFLs are best kept to propagation and cloning — a handy tool for early-stage growth, but limited beyond that.

Pros:

• Very affordable
• Easy to find and set up
• Great for propagation trays or clones
  

Cons:

• Low output
• Not suitable for full grows
  

Best for: Beginners, propagation, and very small spaces.

 

🌈 Light Spectrum Basics

Understanding light spectrum helps you match your lighting to your plant’s needs:

• Blue light → vegetative growth
  
• Red light → flowering and fruiting
  
• UV/Infrared → pest resistance, mould control, and overall health
  

Many modern lights let you shift or combine spectrums for a full grow cycle.

🔌 Things to Consider Before You Buy:

• What’s the size and shape of your grow space?
  Smaller spaces suit LEDs or CFLs; larger areas can handle HID or CMH.
  

• Are you growing short-term or setting up for the long haul?
  CFLs are fine for quick propagation; LEDs or CMH are better long-term investments.
  

• What growth stage are your plants in?
  Blue spectrum for veg (MH, LED); red spectrum for flowering (HPS, LED).
  

• How much heat and power can your space handle?
  HID runs hot and draws more power; LEDs stay cool and efficient.

Still unsure?
Pop in and chat with us at Ōtaki Hydroponics or flick us an email — we’re always happy to help you find the setup that suits your space, your plants, and your goals.