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Buyer's Guide
Under Canopy Lighting: Complete Guide
How Do I Choose Under-Canopy Lighting for My Grow?
Under-canopy lighting hangs below the main canopy to deliver photons upward to the lower bud sites that overhead LEDs can't reach at productive intensity. The right wattage and coverage area depend on how many plants you're running and how much of the lower stem zone you need to illuminate.
What Coverage Do I Need?
Coverage requirements scale with tent size and plant count:
What Should I Look for in Under-Canopy Lighting?
- Spectrum for your stage: Deep red (660nm) is the most common under-canopy spectrum because it drives bud development at lower branch nodes during flower. Full-spectrum bars work equally well for clone zones and vegetative rooms, where the lower canopy needs balanced light rather than a flowering push.
- Bar length and coverage zone: Match bar length to your tent width. A 4-foot bar covers roughly a 4x4 zone beneath the canopy; multi-bar systems link together to cover 4x8 or larger. Starter packs from Faven Lighting and GrowPros Solutions bundle bars with mounting hardware for a single-purchase setup.
- Dimming and scheduling: Pair your under-canopy bars with a lighting controller to run them on the same photoperiod as your overhead light automatically. Some bar systems include built-in dimmers; others require a controller to adjust intensity.
- Under-canopy vs. inter-canopy: If your plants are trained into a dense ScrOG net or you're running a vertical rack, you may need lights placed inside the canopy rather than below it. For those applications, see inter-canopy lighting, which covers ring lights and stem-level fixtures designed for in-canopy placement.
For a current comparison of the top-rated bar systems across brands, see the best under-canopy lighting for indoor grows.
Related Guides
- Best Under Canopy Lighting for Indoor Grows
- Why Every Indoor Grower Should Consider Under Canopy Lighting
- 5 Tips for Selecting the Best Cannabis Grow Lights
Frequently Asked Questions
What is under-canopy lighting?
Under-canopy lighting places supplemental grow lights below the main plant canopy, shining upward to illuminate lower branches and bud sites that overhead LEDs can't reach at productive light intensity. Bar lights and tube lights are the most common formats, running 100-720W depending on grow size.
What is the difference between under-canopy and inter-canopy lighting?
Under-canopy lights hang below the plant structure and shine upward toward lower buds from outside the plant. Inter-canopy lights are placed inside the canopy itself: around individual stems, threaded through ScrOG nets, or between tiers in a vertical rack. Under-canopy lighting suits most bar-light supplemental setups; inter-canopy is the right choice for dense single-plant grows, ScrOG training, or commercial multi-tier racks.
What wattage do I need for under-canopy lighting?
A 4x4 tent with 2-4 plants typically needs 100-150W of supplemental under-canopy light. A 4x8 tent with 4-8 plants needs 200-360W. Commercial rooms with 10+ plants typically run 360-720W of supplemental bar lighting. The goal is to bring lower bud sites to a supplemental PPFD of 150-250 µmol/m²/s rather than matching overhead intensity.
What spectrum is best for under-canopy lighting?
Deep red (660nm) is most effective during the flowering stage because it stimulates bud development at lower lateral sites. Full-spectrum bars are better suited for vegetative rooms and clone zones where you want balanced light for healthy leaf and root development. Most growers running a pure flower cycle choose red-enhanced or deep-red under-canopy bars.
Can under-canopy lights replace primary overhead grow lights?
No. Under-canopy lights are supplemental fixtures. They run alongside overhead lighting to address shaded zones, but they don't provide sufficient PPFD across the whole canopy to work as the sole light source. Typical under-canopy bars deliver 150-300 µmol/m²/s in their target zone; plants need 600-1000 µmol/m²/s at canopy level from the overhead light to drive productive yields.
How do I install under-canopy bar lights?
Bar lights mount horizontally below the canopy, typically attached to tent poles or a cross-frame at mid-plant height. Adjustable stands let you raise or lower the bars as plants develop. Most systems use RJ12 daisy-chain cables to link multiple bars to a single driver or controller, keeping wiring clean across longer zones.
Do under-canopy lights significantly increase energy consumption?
Under-canopy supplemental lighting adds 100-720W to your total draw depending on system size. Modern under-canopy LEDs run at 2.0-2.8 µmol/J efficiency, comparable to quality overhead bars. The power draw is proportional to the supplemental PPFD gain: you're not running a full overhead light, just filling a specific zone. Most growers see the yield increase justify the added draw within one or two cycles.
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