How Many Under-Canopy Light Bars Do You Need? Sizing AG-140 for 4×4 and 4×8 Beds

Short answer: plan on one AG-140 bar for every 4 × 2 ft of bed. That is 2 bars under a 4 × 4 ft bed and 4 bars under a 4 × 8 ft bed. Below is where that number comes from, how to wire it, and what else you need in the cart.

Why the lower canopy needs its own light

Top lights are sized for the top of the canopy. By the time light has passed through the upper leaves, the lower bud sites get a fraction of it, and they stay small and airy. Under-canopy bars put light where the top fixture can't reach, which evens out both light and VPD from the top of the plant to the bottom. In our customers' rooms, adding AG-140 bars as supplemental under-canopy light has increased yield by up to 30%. A 2025 peer-reviewed study measured up to +24.58% and +29.95% yield gains from under canopy lighting (read the study).

Step 1: Count bars by bed size

Each AG-140 covers about 4 × 2 ft of flowering canopy, so the math is simple:

Bed size	Bars (under canopy)	Total PPF, R80 Red (455 µmol/s per bar)	Total PPF, Full Phase (420 µmol/s per bar)	Power draw
4 × 4 ft	2	910 µmol/s	840 µmol/s	280 W
4 × 8 ft	4	1,820 µmol/s	1,680 µmol/s	560 W
5 × 10 ft rolling bench	6	2,730 µmol/s	2,520 µmol/s	840 W
4 × 16 ft bench run	8	3,640 µmol/s	3,360 µmol/s	1,120 W

If you want a rough PPFD figure: 4 R80 Red bars over a 4 × 8 ft bed (about 3 m²) deliver up to roughly 600 µmol/m²/s if every photon landed on the canopy. Real under-canopy numbers are lower because the bars sit between plants and light goes in every direction, so treat this as an upper bound, not a target.

Step 2: Pick a spectrum

• R80 Red Enhanced (AG-140LR): 455 µmol/s at 3.25 µmol/J. The usual choice for flowering rooms and the most output per watt.

• 3K Full Phase (AG-140LW): 420 µmol/s at 3.0 µmol/J. A balanced white spectrum that works from veg through flower, and easier to inspect plants under.

If the bars will only ever run in a bloom room, choose R80 Red. If the same bars move between veg and flower, choose Full Phase.

Step 3: Check your daisy-chain limit

AG-140 bars plug directly into each other end to end, and one connection carries both power and the dimming signal. You only need one power cord per powered run. How many bars fit on one run depends on voltage:

Supply voltage	Bars per powered run	Current per bar
120 V	10	1.24 A
208 V	19	0.69 A
240 V	22	0.60 A
277 V	24	0.56 A

So a 4 × 8 bed with 4 bars is one run on any voltage. A row of four 4 × 8 beds (16 bars) is two runs at 120 V or one run at 208 V and up. Branch-circuit protection and cord sizing still have to follow your local electrical code, so confirm the circuit with your electrician before you order cords.

Step 4: Decide how you'll dim

All AG-140 bars dim 0–100% on a standard 0–10 V signal, so you have three options:

1. Grower's Choice Master Controller: touch screen, two independent groups, sunrise/sunset ramps, up to 100 AG-140 bars directly (50 per side), and up to 1,000 bars per group thanks to the signal booster built into every bar.

2. Trolmaster Hydro-X: works with a Trolmaster LMA14 cable.

3. Any other 0–10 V controller you already run your top lights on.

Step 5: Build the cart

For a single 4 × 8 bed, the simplest route is the AG-140 Under Canopy LED Kit in the 4-bar size. It includes the 4 bars in your spectrum, an 8 ft power cord in your voltage, a 3 ft jumper cord and a pair of adjustable stands for every bar, with or without the Master Controller.

If you are buying bars individually, the full list per powered run is:

• AG-140 bars — one per 4 × 2 ft

• AG-140 Power Cord, 8 ft — one per run, in 120 V, 240 V or 277 V

• AG-140 Jumper Cord, 3 ft — one for each gap in the chain (bars that sit end to end don't need one)

• Adjustable Under Canopy Stands — one pair per bar

• Master Controller — optional

Running cost

Four bars draw 560 W. On a 12-hour flowering schedule that is 6.7 kWh per day. At $0.20 per kWh (check your own rate; commercial rates in California vary widely) that is about $1.35 a day, or roughly $40 a month for the bed. The AG-140 is DLC listed, so it may qualify for a utility rebate; ask your utility about its horticultural lighting program.

Placement tips

• Set the bars on their stands so the LEDs sit just below the lowest bud sites you want to develop, not on the floor.

• Run bars parallel to the long side of the bed so each bar covers a 4 × 2 ft strip.

• The AG-140 is IP65 rated, so it tolerates washdown and IPM spraying; you don't need to pull the bars before spraying.

• Dim to 50–70% for the first few days after installing so lower leaves that have never seen direct light can acclimate.

Browse all under canopy lights, or start with the AG-140 Under Canopy LED Kit.

FAQ

Can I use AG-140 bars as a top light instead? Yes. Use 4 to 8 bars over a 4 × 4 ft area depending on the intensity you need; 8 R80 Red bars give 3,640 µmol/s from 1,120 W.

Do I need a data cable? No. AG-140 bars carry power and dimming signal through the same connection. RJ14 data cables are only for fixtures with RJ ports, such as the ROI series and TSL-800.

What's the warranty? For full warranty details, see growersc.com/warranty or email warranty@growersc.com.

Shipping? Free shipping to the contiguous US (lower 48 states) plus DC. Unused items in original packaging can be returned within 14 days with an approved RMA; a 25% restocking fee applies and the customer pays return shipping.

Questions about a specific room layout? Email info@growerschoice.ag with your bed dimensions and supply voltage and we'll send back a bar count and cart list.