Best Grow Light for a 4x4 Tent (2026)

A 4x4 tent has 16 square feet of canopy, and the light is the single biggest decision in it: it sets your electricity bill, how much heat your fan has to move, and how evenly the plants at the edges grow compared with the ones in the middle.

This guide compares five fixtures sold for 4x4 flowering. Two of them have been mapped by an independent tester, so you can see how much light actually reached the canopy. The other three we can only describe from manufacturer specifications and owner reports, and we say so on each one.

The short answer

• If you want the most evidence behind your purchase, pick the ViparSpectra KS5000 or the Mars Hydro FC-E4800. Both have published, method-stated PAR maps covering a full 4x4.
• If you want a single compact board from a brand with a 5-year light warranty, the Spider Farmer SF4000 is the common choice, but the 2026 revision changed diodes and nobody has published a test of it yet.
• If you already run AC Infinity fans and controllers, the IONFRAME EVO6 keeps everything on one controller and carries a 5-year warranty.
• The Vivosun VS4000 is a lower-wattage option. Its published efficacy differs between Vivosun’s own product page and manual.

Not sure how much light your space needs? Our grow light calculator converts a target PPFD into the PPF and wattage to look for.

What to compare (and what to ignore)

Wall watts, not “equivalent” watts. Ignore “1000W equivalent” claims. Look for the actual power draw, usually stated as something like “480W ±5%”.

PPF (µmol/s) is the total light the fixture emits, measured by the manufacturer in an integrating sphere. It is useful for comparison, but it is not what reaches your plants: some light hits the tent walls and is lost.

Fixture efficacy (µmol/J) is PPF divided by watts. Higher means more light for the same electricity and less heat. Watch for diode ratings presented as if they were the fixture’s: Samsung’s LM301H EVO diode is rated at 3.14 µmol/J, but no fixture built from it delivers that, because drivers and optics lose some energy. HappyHydro’s comparison makes the same point about AC Infinity’s spec sheets.

Average PPFD across the canopy is the number that matters most, and it only comes from a PAR map: a grid of readings taken under the light at a stated height. A single center reading flatters every light. The two independent maps cited below report average, minimum and maximum across a full 48 × 48 inch area.

Warranty matters because drivers fail. Spider Farmer lists 5 years on its SF, SE and G series lights (full coverage in year 1, then paid shipping or discounted replacement); AC Infinity gives 5 years on IONFRAME lights bought from July 1, 2024 (2 years on most other products); Mars Hydro lists 5 years on the FC-E4800.

ViparSpectra KS5000: most even coverage on record

Manufacturer specs: 500 W, six-bar foldable fixture designed for 4x4. ViparSpectra’s own PAR map at 16 inches reports an average of 833 µmol/m²/s (618 minimum, 1,000 maximum) and a “usable” efficacy of 2.40 µmol/J. That is still a manufacturer figure, so we lean on the independent one.

Independent measurement: Coco For Cannabis mapped the KS5000 on February 20, 2022 over a 120 × 120 cm (48 × 48 in) area. At 28 cm (11 in) it drew 488 W and averaged 824.1 µmol/m²/s, counting far-red, for a usable efficacy of 2.43 µmol/J. At the 16-inch height ViparSpectra recommends, PPFD ranged from 582 to 875 µmol/m²/s across the whole map. The reviewer attributes the even spread partly to the frame size: almost 40 inches per side, against roughly 32–34 inches for most competing 4x4 fixtures.

What to know: a frame that large leaves little room to work around it in a 48-inch tent. The test is from 2022; check that the listing you buy is the same KS5000 generation.

Mars Hydro FC-E4800: most measured light per watt

Manufacturer specs: 480 W ±5%, PPF 1,344 µmol/s, 2.8 µmol/J, Bridgelux white diodes with OSRAM 660 nm red, 33 × 33 × 3.1 inches, 5-year warranty. Mars Hydro rates it for a 4x4 maximum and a 3x3 “core” area. Its wholesale site lists the PPF as 1,331 µmol/s, a small inconsistency.

Independent measurement: Coco For Cannabis tested it on June 29, 2021. At 32.5 cm (13 in) it drew 471 W and averaged 751.2 µmol/m²/s across 48 × 48 in, with a 433 minimum and 1,000 maximum, for 1,081.8 µmol/s of usable PPF and 2.3 µmol/J. Raised to 41 cm (16 in), the average was 731.5 with all but one corner above 500. The reviewer suggests running it between 13 and 16 inches in flower.

What to know: the bars slide along the frame. The tester recommends sticking to the tested positions unless you own a quantum sensor. The 2021 unit may differ in detail from the current listing.

Spider Farmer SF4000: the simple board, now with new diodes

Manufacturer specs: 450 W board, PPF 1,171 µmol/s at 120 V, 2.7 µmol/J, rated for 4x4 flowering and 5x5 vegetative growth, recommended 6-inch exhaust fan. Spider Farmer lists a 5-year warranty on its SF series.

The 2026 change: Spider Farmer says the SF4000 has moved to Bridgelux high-efficiency diodes “while maintaining the same output, uniformity, and reliable performance.” Earlier versions used Samsung LM301B. We could not find an independent PAR map of the 2026 Bridgelux version. One independent reviewer, HWGrow, wrote of the related SF2000 that it considers the move away from the tested Samsung configuration a downgrade, while noting Spider Farmer says output is unchanged.

What owners report: the SF series is among the most-discussed lights on the THCFarmer forum. THCFarmer’s guide quotes one member’s SF4000 as performing well “but is slightly too small for a 4x4,” consistent with its point that a single square board strong enough for the center can leave the corners short. Our SF2000 review covers the smaller sibling, which does have independent measurements.

AC Infinity IONFRAME EVO6: for an AC Infinity system

Manufacturer specs: 500 W, 1,680 Samsung LM301H EVO diodes, 4x4 flower / 5x5 veg, IP65, 50,000-hour rated life, model AC-IF6K. AC Infinity quotes 3.14 µmol/J, which is the diode rating rather than the fixture’s efficacy, and a 1,991 µmol/m²/s PPFD figure that is not an average across the canopy.

Warranty: 5 years on IONFRAME lights bought from July 1, 2024 onward, per AC Infinity’s warranty page.

What to know: we could not find a published fixture-level PPF or an independent PAR map for the EVO6, so we cannot compare its delivered light with the two lights above. The case for it is integration: it runs from the same controller as AC Infinity fans, and a 5-year warranty on a premium fixture.

Vivosun VS4000: the lower-wattage option

Manufacturer specs: 400 W, 4x4 flower / 5x5 veg, dimmable in 25% steps, 23.5 × 23.5 × 3.2 inches. Vivosun’s product page lists Samsung LM301 diodes and 2.9 µmol/J. Vivosun’s own manual lists LM301D diodes and “PPE up to 2.7 µmol/J”. We cannot tell which is current, so plan around the lower figure.

What to know: at 400 W you are below the 430–500 W range that THCFarmer members commonly run in a full 4x4, so expect weaker edges than the 480–500 W fixtures. It suits a 4x4 used for vegetative growth, or a slightly smaller canopy.

Two smaller lights instead of one

Coco For Cannabis ran two Mars Hydro TSL 2000 fixtures together in a 4x4 and measured a 750.6 µmol/m²/s average and 1,080.9 µmol/s usable PPF, about the same as the FC-E4800. That test used the earlier Epistar-diode version. The current TSL2000 is listed at 300 W, 717 µmol/s and 2.6 µmol/J with Bridgelux diodes. Two lights also mean two drivers and two hangers, so this route mostly makes sense if you already own one.

How these picks were made

We started from the requirement: enough light for an average of roughly 700 µmol/m²/s across 16 square feet. Lights with a published independent PAR map that met it ranked first. Lights with manufacturer data only came next, with any inconsistencies in that data called out. We did not test any of these fixtures ourselves; see how we research.

Once the light is chosen, size the exhaust for its heat with our inline fan guide, or compare complete 4x4 grow tent kits that bundle a light.