Happy Hydro's Complete LED Buying Guide
Updated buying guide
Buy the light that actually covers your canopy
LED grow light marketing still borrows its vocabulary from HPS, so wattage gets printed in huge type while the two numbers that decide your yield, PPFD across the footprint and efficacy in micromoles per joule, get buried in a spec sheet. This guide walks through the numbers in the order that matters, shows you the math behind each one, and names the specific fixture we would put in your tent.
- Read time: about 9 minutes
- Every fixture named is in stock
- Questions: 716-217-0353
Start here
Pick your tent size, get your light
If you already know your footprint and you do not want to read the theory, this table is the short version. Each row lists the total PPF a single fixture should produce to flower that footprint well, plus the fixture we sell at that spec.
| Footprint | Target PPF, one fixture | Bar style pick | Board style or value pick |
|---|---|---|---|
| 2x2 | 300 to 400 µmol/s | Photontek SQ 200W PRO | All 2x2 lights |
| 2x4 | 600 to 800 µmol/s | AC Infinity IONFRAME EVO3, 280W | Ionboard S24, 200W |
| 3x3 | 700 to 900 µmol/s | AC Infinity IONFRAME EVO4, 300W | Ionboard S33 or Photontek SQ 300W |
| 4x4 | 1,100 to 1,500 µmol/s | AC Infinity IONFRAME EVO6, 500W | Ionboard S44, 400W or Photontek X 465W |
| 5x5 | 1,500 to 2,000 µmol/s | AC Infinity IONFRAME EVO8, 730W | HLG 750 Diablo |
| 5x5 with CO2 | 2,000 µmol/s and up | AC Infinity IONFRAME EVO10, 1000W | Photontek XT 1000W CO2 PRO |
| Commercial rooms, 208 to 480V | Per fixture layout | Gavita RS 1900e, 650W | Gavita Pro RS 2400e, 800W |
Those PPF ranges assume one fixture doing all the work in a sealed tent with reflective walls. Running two smaller fixtures over the same footprint gets you better edge coverage at the cost of more hanging hardware and a second power draw.
The four numbers
PAR, PPF, PPFD, and DLI
These four terms describe the same light at four different scopes: what plants can use, how much the fixture makes, how much lands on a square meter of your canopy, and how much lands there over a full day. Manufacturers quote whichever one flatters the fixture, so knowing which is which is most of the battle.
- PAR, photosynthetic active radiation
- The 400 to 700 nm slice of the spectrum that drives photosynthesis. PAR is a wavelength range, not a measurement, so a fixture advertising "1,000 PAR" is telling you nothing.
- PPF, photosynthetic photon flux
- Total photons per second the fixture emits, in micromoles per second. This is the honest whole-fixture output number and the one to compare between lights.
- PPFD, photosynthetic photon flux density
- Photons per second landing on one square meter, in µmol/m²/s. Always ask at what height and where in the footprint. Center-of-canopy PPFD flatters every fixture ever built.
- DLI, daily light integral
- Total photons delivered to that square meter over 24 hours, in mol/m²/day. This is what the plant actually experiences, and it is the number that tells you whether 18 hours at moderate intensity beats 12 hours at high intensity.
Worked example: 800 PPFD for 12 hours = 800 × 12 × 3,600 ÷ 1,000,000 = 34.6 mol/m²/day
Most fruiting and flowering crops run well between 30 and 45 mol/m²/day without added CO2. Leafy greens and herbs are happy in the 12 to 17 range, which is why a 200W fixture that looks underpowered for flowering is plenty for a salad tent.
Intensity targets
How much PPFD each stage wants
PPFD by growth stage
- Clones and cuttings: 75 to 150 µmol/m²/s
- Seedlings: 100 to 300 µmol/m²/s
- Vegetative: 300 to 600 µmol/m²/s
- Flower: 600 to 900 µmol/m²/s
- Flower with CO2 enrichment: 900 to 1,200 µmol/m²/s
Why dimming matters more than peak output
A fixture that only runs wide open forces you to raise it during veg, which widens the beam and wastes light on the tent walls. Ten-level or 0 to 100 percent dimming lets you keep the fixture at a fixed height and drop intensity instead, so your footprint stays the same from seedling through harvest.
Buy the fixture sized for flower, then dim it back. Buying small and hoping to make it up with hang height does not work.
Nobody should take a manufacturer's PPFD claim on faith, including ours. A PAR meter costs less than the yield you lose to two seasons of guessing, and it turns hang height from an argument into a measurement.
Efficacy and running cost
Micromoles per joule is the spec that follows you home
Efficacy is PPF divided by watts drawn, written as µmol/J. It tells you how much usable light you get per unit of electricity, and it is the only spec on the sheet that shows up on your power bill every month for the next decade. Anything at or above 2.7 µmol/J is solid for a home tent. Diode-level ratings above 3.0 µmol/J represent the current top of the market.
Worked example: 280W for 12 hours at $0.16/kWh = 0.28 × 12 × 30 × 0.16 = about $16 per month
Two fixtures, same footprint
A 2.5 µmol/J fixture needs roughly 20 percent more watts than a 3.0 µmol/J fixture to hit the same PPFD. Over a 12 hour flower cycle, that gap is real money and real heat.
Heat is the second bill
Every watt you do not convert to photons becomes heat your exhaust fan has to move. Lower efficacy raises your electric bill twice: once at the light, once at the fan and the air conditioner.
Where the driver sits
A removable driver mounted outside the tent takes its heat load with it. On AC Infinity IONFRAME fixtures the driver detaches on a 6 ft cable, which matters most in July.
Our pick for most home growers
If you are running a 2x4 tent, buy the EVO3
AC Infinity IONFRAME EVO3, 280W
The 2x4 is the most common tent we ship, and the EVO3 is the fixture that answers every question on this page at once. It runs 840 Samsung LM301H EVO diodes rated at 3.14 µmol/J per chip, delivers 1,745 PPFD at center canopy across a 2x4 flower footprint, and includes a schedule controller with ten brightness levels and sunrise and sunset ramping. The SOSEN driver detaches and mounts outside the tent.
- 280W
- 3.14 µmol/J per diode
- 1,745 PPFD center
- 2x4 flower, 3x5 veg
- ETL certified
- IP-65
- 2 year warranty
Spectrum runs 395 nm through 730 nm, with three Seoul UV diodes, 27 OSRAM 660 nm reds, and three OSRAM far-reds alongside the 3000K and 5000K whites. Rated lifespan is 50,000 hours.
View the IONFRAME EVO3Tightest budget
Ionboard S24, 200W
Board style, no removable driver, no bar layout. Covers the same 2x4 for less money and runs cooler than anything in the old blurple category.
Veg room or mother plants
HLG 250 Veg Pro
A dedicated veg spectrum with extra blue keeps internodes tight and leaves broad. Worth it only if you run veg and flower in separate spaces.
Clones and lower canopy
Mammoth clone and inter-canopy bars
Two 50W bars per box, mounted low or sideways to light the parts of the plant your overhead fixture cannot reach.
Fixture style
Bar style or board style
Both are full spectrum white LED. The difference is how the diodes are distributed and what that does to your footprint and your ceiling height.
| Bar style | Board style | |
|---|---|---|
| Diode layout | Many low-wattage diodes spread across several bars | Fewer, harder-driven diodes on one or two panels |
| Footprint shape | Wide and even, fills rectangular tents corner to corner | Concentrated, stronger in the center than at the edges |
| Hang height | 6 to 12 inches above canopy is workable | Usually 28 inches or more, needs vertical room |
| Canopy penetration | Moderate, favors flat even canopies | Deeper into tall plants from a single point |
| Best growing style | Sea of green, screen of green, short ceilings | Fewer large plants grown tall |
| Examples we stock | IONFRAME EVO6, Photontek X 1000W | HLG 750 Diablo, Ionboard S44 |
Ceiling height decides this more often than growing style does. If your tent is 6 ft tall and you are growing in 5 gallon pots, a board fixture that wants 30 inches of clearance leaves you very little plant.
Spectrum
Full spectrum white, and what to add to it
A quality full spectrum white fixture will take a plant from seedling to harvest without a spectrum change. Single-wavelength blurple panels are the previous generation and are worth replacing rather than supplementing. Where supplemental bars earn their place is at the edges of the spectrum and the edges of the canopy.
UV, 365 to 400 nm
Added late in flower as a stress input. Run it on a separate schedule from your main light so you can control exposure, and wear eye protection in the tent while it is on.
Far red, 730 nm
Triggers the Emerson effect alongside red light and speeds the transition to dark. Most current bar fixtures already include a few far-red diodes, so check the spec before you add more.
Under canopy and side lighting
Slim bars mounted below or beside the canopy put light on lower bud sites that never see the overhead fixture. This is the cheapest yield you can add to an existing tent.
Control and automation
What a controller buys you that a wall timer does not
A wall timer handles
- On and off at a fixed hour
- Nothing else
Perfectly fine if your fixture has its own dimmer and you are running one light in one tent.
A UIS controller adds
- Dimming on a schedule, not just a knob you forget to turn
- Sunrise and sunset ramps instead of a hard on at full power
- Temperature and VPD triggers that cut light intensity when the tent runs hot
- One app controlling light, fan, humidifier, and outlets together
- Data logging, so you can see what the tent did overnight
AC Infinity fixtures pair with the Controller 69 Pro, the Controller 69 Pro+, and the Controller AI+. Buy any of the three alongside an eligible AC Infinity light and 25 percent comes off the controller automatically at checkout, no code needed. Browse the rest at lighting controllers.
Before you click buy
Fit, certification, and warranty
Physical fit
- Measure the fixture against your tent's interior width, not the tent's label size
- Check your crossbar weight rating before hanging anything over 30 lb
- Leave vertical room for hang height plus pot height plus plant height
- Confirm where the driver sits and whether the cable reaches a duct port
- Check voltage: North American tents run 120V, and Gavita commercial fixtures need 208 to 480V
Certification and warranty
- UL or ETL listing is required for licensed commercial rooms in the US, and is worth having at home for insurance reasons
- IP-65 means the fixture tolerates dust and water spray, which matters in a humid tent
- Two to three years is the current standard warranty on quality fixtures
- Read whether the warranty covers the driver separately from the diodes, since drivers fail first
- We are an authorized dealer for every brand here, so the manufacturer warranty is intact
Questions
Frequently asked questions
Can I just use a bigger light in a smaller tent and dim it?
Up to a point, yes, and it is a reasonable way to leave room to expand. The limit is footprint shape, not intensity. A fixture PAR-mapped for 5x5 hung in a 3x3 will throw a large share of its output onto the tent walls no matter how far you dim it. Matching the footprint shape first, then dimming for stage, is the better order.
How many watts per square foot should I be aiming for?
Watts per square foot is a leftover from HPS and it breaks down across LED fixtures with different efficacy. A 3.0 µmol/J fixture and a 2.4 µmol/J fixture at the same wattage deliver noticeably different light. Compare PPF and target PPFD instead. If you want a rough sanity check, modern LED flowering runs somewhere near 30 to 40 watts per square foot, but treat that as a gut check and not a spec.
Is a PAR meter worth buying for one tent?
If you plan to grow for more than a season, yes. It settles hang height in ten minutes, shows you how much light your corners are actually getting, and tells you whether dimming to 60 percent put you where you thought it did. Phone apps get you in the neighborhood but read poorly under LED spectra. Our PAR meters start well under the price of a mid-range fixture.
Do I need separate veg and flower spectrums?
Not for a single-tent grow. A full spectrum white fixture handles both stages, and dimming covers the intensity difference. Separate veg spectrum fixtures with extra blue are worth it when you keep a dedicated veg space or mother room, where tighter internodal spacing and stockier growth pay off before plants move to flower.
How much will an LED raise the temperature in my tent?
Budget roughly 5 to 10°F above ambient for a 280W fixture in a 2x4 with the driver inside, more in a sealed space and less with the driver mounted outside. You will still need active exhaust. Size your inline fan to exchange the tent's air volume roughly once a minute, and pair it with the same controller running your light so it responds to temperature automatically.
Are two smaller lights better than one big one?
For edge coverage in a square footprint, often yes. Two fixtures overlap in the middle and fill the corners better than a single centered unit. The trade-offs are a second power cord, more hanging hardware, and usually a slightly higher total cost for the same PPF. In rectangular tents like a 2x4, a single bar fixture sized to the footprint is usually the cleaner answer.
What if the light arrives damaged or defective?
If you receive a defective or damaged unit, email us a photo at help@happyhydro.com and we'll take care of you. For change-of-mind returns, we accept returns within 30 days for most items in new, resalable condition. If you're not sure whether this product is right for your setup, call us first at 716-217-0353. We'd rather answer your questions before you order.
Why buy a grow light from Happy Hydro?
Happy Hydro has been selling growing equipment since 2006. We've carried AC Infinity, HLG, PhotonTek, Gavita, and Mammoth Lighting for years because the systems work great and customers who buy them leave happy. Have questions before you order? Call 716-217-0353 or email help@happyhydro.com. We're easy to reach and happy to help!
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Browse the full lineup
Fifty-plus fixtures from AC Infinity, Horticulture Lighting Group, PhotonTek, Gavita, and Mammoth Lighting, filterable by coverage area and wattage. If you would rather buy the tent, light, fan, and filter together, the grow kits are already matched.
Questions? We're easy to reach.
Happy Hydro has been serving growers since 2006. Call or email us before you order, after you order, or any time something comes up. When you're happy, we're happy.
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