I'll be honest with you: this is not one of those articles that ends with 'and the best greenhouse grow light is X.' If you're a distributor, you already know that the 'best' SKU depends on who is buying it. A fixture that helps a tomato grower push through December in Ontario is not the same fixture an indoor herb farm in California should run 18 hours a day.
I spent six years as a procurement manager for a 40-person horticulture business with a lighting budget of about $150,000 a year. I reviewed specs from a lot of grow light manufacturers, made expensive mistakes, and eventually moved to the supplier side. Today I help hortilux work with greenhouse lighting distributor partners. This greenhouse lighting specification guide is the conversation I wish someone had handed me before I wasted roughly $14,000 in my second year stocking the wrong lamp.
Start With Three Scenarios, Not One Shopping List
There is no universal grow light specification. But there is a reliable way to approach the decision: sort your customers by how they use light. Once you know which group you're serving, the specs that matter become much clearer.
I use three groups when I talk through product selection with distributors. They are not perfect categories, but they cover almost every B2B buying pattern I have seen in horticultural lighting.
Scenario 1: Your Customers Grow Commercial Crops in Greenhouses
If your buyers are commercial greenhouse growers raising tomatoes, peppers, cucumbers, or berries, their lights usually supplement sunlight rather than replace it. These customers talk in daily light integral, photoperiod hours, and grams per square meter. A fixture needs to fit into an existing greenhouse structure, tolerate high humidity, and deliver even light distribution over the canopy.
In this scenario, the single most useful specification is usable PPF at the customer's mounting height—not the peak PPF printed in the marketing sheet. PPF tells you how many photons the fixture emits in total; it does not tell you how those photons land on a 20-meter greenhouse bay. Ask for a PPFD map at the heights your customer actually hangs fixtures. If a grow light manufacturer can't provide one, that's an early red flag.
Here's where my advice gets less intuitive: do not default to the highest-efficacy fixture. I spent years assuming that a 3.2 μmol/J rating was automatically better than 2.8 μmol/J. But efficacy is only one input into the customer's return-on-investment calculation. If a greenhouse runs supplemental light only four to five months per year, that efficiency premium can take years to pay back. The cheapest light is rarely the cheapest, and the most efficient one is also rarely the most profitable for the grower. Calculate payback before you recommend.
If you're considering a hortilux grow lamp for this group, start with crop DLI targets, then greenhouse structure, then fixture specs. We publish PPFD maps and dimming data specifically because distributors need to make that calculation.
Scenario 2: Your Customers Run Indoor Farms or Controlled-Environment Rooms
This is where lights are the sun. Indoor vertical farms, tissue culture rooms, and propagation racks run lights 16 to 24 hours a day, usually with no natural daylight. Every point of efficacy translates into operating cost, so it's tempting to assume the highest μmol/J fixture is the automatic choice. It isn't.
At high operating hours, what matters even more is usable light on the crop plane. I've compared fixtures with excellent lab PPF and poor on-rack uniformity. At the edges of a rack, PPFD fell off hard, so the farm had to either raise the fixture and lose a shelf level or accept slower growth at the borders. A fixture with slightly lower max PPF but a wider, more even distribution can outperform it commercially.
Ask for spatial PPFD maps at actual mounting heights. Also test the dimming range. Indoor farms often want to simulate sunrise and sunset or run low-light crops at 10% output. If a fixture flickers or shuts off below 30%, it will drive your customer crazy over a year. And check how the driver responds to voltage dips. Growing rooms are full of refrigeration and fans; voltage stability matters.
If this is your market, ask any grow light manufacturer—including us at hortilux—for a hortilux grow light spectrum chart, a PPFD map, and a dimming curve. If they don't share those documents readily, move on.
Scenario 3: You're New to Horticultural Lighting Distribution
Let's say you're a distributor or wholesale supplier adding horticultural lighting for the first time. You may not yet know whether your customers are greenhouse growers or indoor farmers. That's fine, but it changes the buying strategy.
Resist the container-load temptation. Instead, choose one or two workhorse fixtures and learn them deeply. Get sample units, run them on a bench, take your own measurements, and photograph the light distribution in a real greenhouse. If your supplier offers OEM or private label, ask what happens when lead times stretch and whether tooling costs are separate from the per-unit quote.
One warning from my procurement years: I once told a supplier, 'make sure mounting hardware is included.' They heard, 'mounting hardware if it happens to fit in the box.' The fixtures arrived without brackets and installation stopped for two weeks. In fairness, the supplier wasn't hiding a fee—I was the one who didn't put the requirement in writing. Put every assumption into your purchase order. If it is not on the order, it will not arrive.
The Question Most Distributors Forget to Ask
The most valuable question in B2B lighting procurement has nothing to do with light output. It's this: 'What is not included in the quoted price?'
'What is NOT included?'—that is the question to ask before 'what is the price?'
I have mixed feelings about low price quotes. On one hand, I understand why sales teams want to appear competitive. On the other, an incomplete quote usually turns into an expensive surprise. In Q4 2024, I compared two quotes for similar 600W fixtures. One quote came in at $319 per unit. The other at $358. The first looked like a no-brainer until I added freight, import handling, and spare drivers—about $46 more per unit. The $358 quote had freight, insurance, and a spare driver for every 25 fixtures built into the line item. Bottom line: clarity was worth more than the discount.
Transparent pricing is not about being the most expensive or the least expensive. It's about being able to compare actual totals. At hortilux, we itemize shipping terms, warranty exclusions, and certification documents because hidden fees destroy trust faster than high prices do.
Before placing your first stocking order, ask for these documents and put them in the contract:
- Photometric test report (IES file, LM-79 data) and PPFD maps at realistic mounting heights.
- LM-80 and TM-21 data for LED lifetime projections at the actual operating current.
- Safety certifications for the target market, for example UL 8800 for U.S. installations or CE marking for the EU. Verify current requirements at the official certification body; DLC horticultural listing may also apply, so check dlc.org for current program requirements.
- A written warranty that states which components are covered, who pays for return freight, and whether advance replacement units are available.
Also ask what happens after a warranty claim. Drivers, for example, are usually a replaceable component. If the supplier cannot provide spare drivers quickly for a container of fixtures, your end customer will be staring at dark plants.
How to Tell Which Scenario You're In
Still unsure? Work through these three questions.
- Do your customers have a greenhouse with natural daylight? Yes means Scenario 1, and the conversation should focus on supplemental DLI and payback. No means Scenario 2, and the focus shifts to spectral quality, uniformity, and dimming behavior.
- How many hours per day will the fixture actually run? If it is under roughly 6,000 hours per year, payback dominates the decision. If it runs more than 18 hours a day, operating cost and uniformity dominate.
- Do you already have an established customer base for horticultural lighting? If you're still building that base, treat yourself as Scenario 3 and minimize your early inventory risk.
If you answered yes to the first question but you aren't sure whether your customers can justify LED economics yet, start the conversation with a simple audit: what is their current fixture wattage, how many hours do they run, and what electricity rate are they paying? That will tell you more than any spec sheet debate.
Bottom Line
Don't buy a grow light. Buy a specification that fits a customer, a total cost that includes everything, and a supplier who will put claims in writing.
I'm not going to claim hortilux is the only grow light manufacturer worth calling. There are good fixtures from several companies, and some of them are sold by distributors we respect. But the hortilux wholesale program is built around the kind of transparency I demanded as a buyer: line-item quotes, documented specifications, and warranty language that doesn't need a lawyer to translate. If you're a greenhouse lighting distributor comparing suppliers, ask for those things before you ask for a discount. The supplier who gives them to you quickly is the one worth testing.
Have a look at the current hortilux grow lamp and hortilux grow light lines, and check whether the spec documents line up with the checklist above. As of January 2025, those documents are public on request—and they should be.