Sourcing LED Grow Lights From China: PPFD, Spectrum, and Why Watts Lie

Grow lights are the category where the numbers are most actively dishonest, and where a savvy buyer can win big simply by asking the right questions. The wattage on the box rarely means what a customer thinks it means, and the spectrum claims are often copied from a competitor's page. If you are sourcing for an indoor-grow brand, this is what to look for.

"1000W" is not 1000 watts

The watt number on most cheap grow lights is a marketing label inherited from the old HID (high-intensity discharge) era, meant to describe "equivalent to a 1000W HPS lamp." It is not the actual power draw. A light sold as "1000W" might pull 100 to 150 watts from the wall.

Three real numbers to demand:

Actual power draw at the wall, in watts, measured with a meter — not the label. Ask for a photo of a power meter on the unit.
PPF (Photosynthetic Photon Flux), in micromoles per second (µmol/s). This is the total light output that plants can use. It is a physical measurement and hard to fake if the factory provides a test report.
PPFD (PPF Density), in µmol/m²/s, at a stated height and covering a stated area. This is what plants actually receive and what growers care about. Crucially, PPFD must be quoted at a distance and a coverage footprint, or it means nothing.

A spectrum that folds PPFD "at 6 inches directly under the center" is the grow-light equivalent of CADR quoted only in boost mode. Ask for the PPFD map across the stated footprint at the recommended hanging height for the flowering stage.

Efficacy is the honest efficiency metric

Divide PPF by actual wall watts and you get µmol/J — efficacy. Good modern LED fixtures run 2.3 to 2.8 µmol/J; the very best commercial fixtures push past 3.0. A fixture claiming "high efficiency" without a number is not claiming anything. A fixture at 1.5 µmol/J is a space heater with a nice color.

Higher efficacy costs more in diodes and drivers but pays the customer back in electricity. For a commercial buyer that math is not optional, so quote efficacy as the headline, not the fake wattage.

Spectrum: match the goal, do not chase the rainbow

You will see everything from "full-spectrum" blurple to broad white. What matters:

Vegetative versus flowering. Veg wants a higher proportion of blue; flowering wants strong red, particularly the deep-red band around 660 nm. Many modern full-spectrum fixtures cover both reasonably and rely on the grower to change the photoperiod rather than swapping lights.
Red to blue ratio as a stated number, and whether the fixture includes far-red (730 nm) for the Emerson effect. This is a real upgrade for flowering, but only if the driver channels support it independently.
White-light working spectrum. Growers increasingly want to see plant health with their own eyes, and broad-white diodes make that possible. That is a feature, and it is worth asking about explicitly rather than accepting blurple.

Drivers and diodes are the cost, and the failure point

Ask which driver brand and which LED brand. The diodes (LED chips) are the single largest line item, followed closely by the driver and the heatsink. Top-bin diodes from a known manufacturer are binned for consistent output and color; no-name diodes are not, and their output sags and shifts over thousands of hours.

Ask for the diode binning and the LM-80 data if available. For the driver, an isolated constant-current design with real margin is worth the extra cost — it is what keeps the fixture alive in a hot tent. Which brings us to heat.

Thermal design decides lifespan

LED output degrades with temperature, and grows degrade fast. The heatsink and the driver thermal path are where cheap fixtures cut corners.

Weigh the fixture, or ask for its weight. Passive heatsinks are heavy because they contain metal; if the "bar-style" fixture is suspiciously light, the metal is not there.
Ask for the junction temperature or the case temperature under load at rated power. If the factory has no idea, that tells you everything.
Consider the environment. A passive-cooled bar is right for a large tent; a small unit with a loud fan in a bedroom tent is a return waiting to happen.

Certifications and channel realities

Grow lights are lighting products and carry the usual obligations — CE and RoHS for the EU, plus the relevant EN lighting standard; UL/ETL for the US. Beyond that:

If you sell in the US, some channels treat high-power LED grow fixtures as commercial lighting and want safety listing. Confirm your channel's requirement before you commit.
Drivers and any wireless control module need their own certification for the destination market.
Watch the spectrum claims for regulatory overreach. UV diodes, where present, are regulated in several markets.
Waterproof rating (IP) matters if the fixture hangs in a humid grow room. "Damp location" is not the same as a real IP rating; ask for the IP number.

Honest summary

Buy on three numbers: actual wall watts, PPF in µmol/s, and efficacy in µmol/J. Then check the PPFD map across the coverage area at the recommended height, the diode and driver brands, and the thermal spec. When a supplier cannot produce those, the low price is not a bargain — it is a product that will be returned by every serious grower who buys it.