How to Compare Under Canopy LED Lights: 4 Numbers That Matter

Under canopy LED bars look almost identical in photos: a four-foot bar, a row of diodes, a connector on each end. The spec sheets are where they differ. Four numbers tell you most of what you need before you buy for a flower room.

1. PPF: how much light the bar makes

PPF (photosynthetic photon flux) is the total light a fixture puts out each second, in µmol/s. Four-foot under canopy bars on the market today run from roughly 325 to 455 µmol/s. A bar with more PPF lights more lower bud sites, so you need fewer bars, fewer stands and fewer connections to reach the same light level under the canopy.

2. Efficacy: how much light you get per watt

Efficacy is PPF divided by watts, in µmol/J. Current under canopy bars range from about 2.6 to 3.25 µmol/J. The difference shows up on the power bill every day the room runs: at 3.0 µmol/J a bar uses about 13% less electricity than a 2.6 µmol/J bar to make the same light. If a spec sheet does not list efficacy, divide the PPF by the wattage yourself.

3. Bars per run: how many you can chain on one power cord

Under canopy bars daisy-chain, and the limit depends on your voltage. As a reference, the AG-140 chains up to 10 bars at 120V, 19 at 208V, 22 at 240V and 24 at 277V on one power cord. A higher limit means fewer power drops per bench and less electrical work. Check the limit at the voltage you will actually use, and remember that a chain cannot jump from one bench to the next without a jumper cord.

4. Cost per µmol/s: the fair way to compare price

Sticker price per bar hides the difference in output. Divide the price by the PPF instead. A $139 bar that makes 420 µmol/s costs $0.33 per µmol/s; the same price at 455 µmol/s works out to $0.31. Run the same math on any bar you are considering, and add the cords and stands you need, since most bars are sold without them.

Also check before you order

Ingress rating: under canopy bars sit in the splash zone, so look for IP65 or higher. Safety listing: look for a listing to UL 8800, the standard for horticultural lighting. DLC listing: many utility rebate programs require it, and eligibility and amounts depend on your utility's program. Dimming: 0-10V works with most controllers. Warranty: ask who services it and where.

Where the AG-140 lands

The AG-140 under canopy bar is 140W and makes 420 µmol/s at 3.0 µmol/J in 3K Full Phase, or 455 µmol/s at 3.25 µmol/J in R80 Red. It is IP65, ETL listed to UL 8800 and DLC listed, and runs on 120-277V. If you want bars, cords and stands in one box, see the AG-140 under canopy kit in 2-bar and 4-bar sizes.