The Most Efficient Grow Lights by µmol/J
One number decides how much of your electricity becomes light. Across this field it varies by nearly a factor of two, which is roughly $40 a winter.
By Scooter M. — An enthusiast who's genuinely into this. I read the manuals, compile the published specs, and do the math. No lab coat.
Published · How we pick
Photographs on this site are licensed stock and are illustrative of the fixture type. We do not own the units we write about.
How this page is funded: the buy links here are Amazon Associates links, and we earn a commission on qualifying purchases at no extra cost to you. We have not been paid to feature anything on this page, we accept no free product, and commission plays no part in the ranking. Full disclosure.
We have not tested these units. Everything below comes from the manufacturer’s own published specifications, or from arithmetic we have shown our working for. Where a figure is not published, we say so instead of estimating one. Read the method.
Quick picks
Efficacy is photons out per joule in. Where a manufacturer publishes it we quote theirs; where they publish photon output and wattage but not efficacy, we divide and label it as ours; where they publish neither, the cell says so rather than guessing. Tap a row for the full write-up.
| # | Product | Best for | Efficacy | Price |
|---|---|---|---|---|
| 1 |  VIVOSUN VS1000 Samsung LM301 diodes and a published 2.75 umol/J — the highest efficacy claim on this list, though the photon output it implies is never printed anywhere. | Highest published figure | 2.75 umol/J | |
| 2 |  AC Infinity IONBOARD S22 The highest published efficacy of any fixture here at 2.7 umol/J, on Samsung LM301H diodes, with dimming in real 20% steps rather than a vague knob. | High and specific | 2.7 umol/J | |
| 3 |  Spider Farmer SF1000 Publishes PPF to two decimal places and an efficacy figure that actually divides out of it. That internal consistency is rarer in this category than it should be. | Efficacy that checks out | 2.5 umol/J | |
| 4 |  Mars Hydro TS 1000 The most photons of anything on this list, and one of only three fixtures here that publishes both PPF and efficacy so the claim can be checked against itself. | Efficient at high output | 2.3 umol/J | |
| 5 |  SANSI 36W BR30 Grow Light Bulb The rare grow bulb that publishes both PPF and a PPFD figure with the measurement distance attached, which is the only reason it can be sized honestly. | Best of the bulbs | 1.82 umol/J (ours) |
The reasoning
Photon efficacy — micromoles of usable light per joule of electricity — is the single most decision-relevant number on a grow light spec sheet. It sets how much light you get for a given draw, which means it sets both the fixture you need and what it costs to run for the next five years.
It is also the number most brands are quietest about. Of the nine fixtures on this site, four publish an efficacy figure, two can have one derived from other published figures, and three publish nothing usable at all.
2.75 µmol/J against 1.39 µmol/J. The same amount of light, for nearly double the electricity.
The ranking
Published figures are labeled as published. Derived figures are our arithmetic on numbers the manufacturer published, and the working is given. Nothing here is estimated.
| Rank | Fixture | µmol/J | Published or derived |
|---|---|---|---|
| 1 | VIVOSUN VS1000 | 2.75 | Published |
| 2 | AC Infinity IONBOARD S22 | 2.7 | Published |
| 3 | Spider Farmer SF1000 | 2.5 | Published; 249.21 ÷ 100 W = 2.49 confirms it |
| 4 | Mars Hydro TS 1000 | 2.3 | Published |
| 5 | SANSI 36W BR30 | 1.82 | Derived: 65.6 µmol/s ÷ 36 W |
| 6 | Soltech Aspect Gen 2 | 1.39 | Derived: 50 µmol/s ÷ 36 W |
| — | Barrina T5 4ft | Not published | No photon figure of any kind |
| — | ViparSpectra P1000 | Not published | No photon figure of any kind |
| — | GooingTop clip light | Not published | No manufacturer spec sheet exists |
Why VIVOSUN leads and still is not our default recommendation
VIVOSUN publishes the highest figure here at 2.75 µmol/J. It also publishes no PPF, so there is no second number to divide against and no way to check the claim against itself. Spider Farmer’s 2.5 is a lower number that we can verify: 249.21 µmol/s divided by 100 W is 2.49, which rounds to the published 2.5. That internal consistency is worth something real.
This is the recurring tension on this site. A higher unverifiable number is not obviously better than a slightly lower verifiable one, and we would rather say so than pretend the ranking settles it.
What the difference actually costs
Target 300 µmol/s of photon output, run 14 hours a day for five months (150 days).
At 2.75 µmol/J: 300 ÷ 2.75 = 109 W. 109 × 14 × 150 ÷ 1000 = 229 kWh = $42.00 at 18.34 cents.
At 2.3 µmol/J: 300 ÷ 2.3 = 130 W. 130 × 14 × 150 ÷ 1000 = 273 kWh = $50.07.
At 1.39 µmol/J: 300 ÷ 1.39 = 216 W. 216 × 14 × 150 ÷ 1000 = 454 kWh = $83.26.
The top-to-bottom gap is about $41 a winter for the same light. Over five winters that is roughly $200, which is more than most of these fixtures cost.
The form factor tax
Notice that both derived figures at the bottom of the table are the non-panel form factors. The SANSI bulb and the Soltech pendant are the two most efficient in their own categories, and both sit well below every panel. That is not poor engineering; it is what you pay for a screw-in fitting or for a fixture designed to be visible in a living room.
Worth knowing before you compare a bulb against a panel and conclude the bulb is bad value. It is a different product solving a different problem, and the efficiency gap is the price of the form factor.
Where efficacy stops mattering
At small scale, honestly, it barely does. A single 36 W bulb run 12 hours a day costs about $2.38 a month at the average rate. Halving its efficacy would cost you $2.38 a month more — an amount that should not drive a purchase decision.
Efficacy earns its place as a criterion when you are running several hundred watts for months at a time, or when two fixtures are otherwise close and you need a tiebreaker. Price your own case in the running-cost calculator before deciding how much it should weigh.
Every pick in full
VIVOSUN VS1000
LED panelHighest published figure
Samsung LM301 diodes and a published 2.75 umol/J — the highest efficacy claim on this list, though the photon output it implies is never printed anywhere.
What VIVOSUN publishes
- Power draw
- 100 W (source)
- Efficacy
- 2.75 umol/J (source)
- Stated coverage
- 2 x 2 ft (source)
- Spectrum
- 380-780 nm, including 660 nm and 730 nm; 3000 K and 5000 K (source)
- Diodes
- Samsung LM301 (source)
- Dimming
- Yes, four dimming levels, daisy chain (source)
Our arithmetic
- Photon output implied by the published wattage and efficacy: about 275 umol/s
100 W x 2.75 umol/J = 275 umol/s. Our arithmetic from VIVOSUN's two published figures, not a VIVOSUN figure.
What VIVOSUN does not publish
- PPF in umol/s
- PPFD at any stated distance
- Rated lifespan
Who should skip it
Skip it if you want the efficacy claim independently checkable. With no published PPF there is no second figure to divide against, so the number has to be taken on trust.
AC Infinity IONBOARD S22
LED panelHigh and specific
The highest published efficacy of any fixture here at 2.7 umol/J, on Samsung LM301H diodes, with dimming in real 20% steps rather than a vague knob.
What AC Infinity publishes
- Power draw
- 115 W (source)
- Efficacy
- 2.7 umol/J (source)
- PPFD
- 1098 PPFD (no measurement distance published) (source)
- Stated coverage
- 2 x 2 ft (source)
- Spectrum
- Samsung LM301H, plus 660 nm, 730 nm, 3000 K, 6500 K (source)
- Diodes
- 272 diodes (source)
- Dimming
- Yes, 0-100% in 20% increments (source)
- Dimensions
- 30.0 x 30.0 cm board, 1.1 cm thick (source)
- Rated life
- 50,000 hours (source)
Our arithmetic
- Photon output implied by the published wattage and efficacy: about 311 umol/s
115 W x 2.7 umol/J = 310.5 umol/s. AC Infinity does not print PPF directly, so this is our arithmetic from two figures it does print.
What AC Infinity does not publish
- PPF in umol/s — only efficacy is given, so photon output has to be derived
- The measurement distance for the 1098 PPFD figure, without which the number cannot be compared to anything
Who should skip it
Skip it if you want to place it by the numbers. AC Infinity prints 1098 PPFD with no measurement distance attached, which makes that figure impossible to use or compare.
Spider Farmer SF1000
LED panelEfficacy that checks out
Publishes PPF to two decimal places and an efficacy figure that actually divides out of it. That internal consistency is rarer in this category than it should be.
What Spider Farmer publishes
- Power draw
- 100 W +/-5% at 100-277 V AC (source)
- PPF (photon output)
- 249.21 umol/s (source)
- Efficacy
- 2.5 umol/J (source)
- Stated coverage
- 2 x 2 ft core, 3 x 3 ft maximum (source)
- Spectrum
- 650-665 nm, 730-740 nm, 2800-3000 K, 4800-5000 K (source)
- Diodes
- Bridgelux (source)
- Dimming
- Yes, dimming knob (source)
- Dimensions
- 32.5 x 29.0 x 5.9 cm (source)
- Rated life
- 55,000 hours (source)
Our arithmetic
- Does the published efficacy check out against the published PPF?: Yes — 2.49 umol/J computed against 2.5 umol/J published
249.21 umol/s / 100 W = 2.4921 umol/J. The published 2.5 umol/J is that number rounded. Not every brand's two figures agree like this, which is exactly why we divide them. - Average PPFD across its 2 x 2 ft core footprint: about 536 umol/m2/s
2 ft x 2 ft = 4 sq ft = 0.372 m2. 249.21 / 0.372 = 670 umol/m2/s at perfect uniformity; at a 0.8 uniformity factor, about 536 umol/m2/s.
Who should skip it
Skip it if raw output is what you are buying — the TS 1000 delivers 38% more photons per second, at the cost of 50 W more draw.
Mars Hydro TS 1000
LED panelEfficient at high output
The most photons of anything on this list, and one of only three fixtures here that publishes both PPF and efficacy so the claim can be checked against itself.
What Mars Hydro publishes
- Power draw
- 150 W +/-5% at 100-277 V AC (source)
- PPF (photon output)
- 343 umol/s (source)
- Efficacy
- 2.3 umol/J (source)
- Stated coverage
- 2.5 x 2.5 ft vegetative, 2.3 x 2.3 ft flowering (source)
- Spectrum
- 660-665 nm, 730-740 nm, 3000 K, 5000 K (source)
- Diodes
- Bridgelux (source)
- Dimming
- Yes, 0-100% dimmer knob (source)
- Dimensions
- 406 x 326 x 50 mm (source)
Our arithmetic
- Average PPFD across its stated 2.5 x 2.5 ft vegetative footprint: about 470 umol/m2/s
2.5 ft x 2.5 ft = 6.25 sq ft = 0.581 m2. 343 umol/s divided by 0.581 m2 = 590 umol/m2/s at perfect uniformity; applying a 0.8 uniformity factor gives about 472 umol/m2/s average. - Electricity used at 14 hours a day for 30 days: 63.0 kWh a month
150 W x 14 h x 30 d / 1000 = 63.0 kWh.
Who should skip it
Skip it if you are lighting a bookshelf. 343 umol/s concentrated into a 2.5 ft square is far more light than a monstera wants, and you pay 150 W to deliver it.
SANSI 36W BR30 Grow Light Bulb
Grow bulbBest of the bulbs
The rare grow bulb that publishes both PPF and a PPFD figure with the measurement distance attached, which is the only reason it can be sized honestly.
What SANSI publishes
- Power draw
- 36 W (source)
- PPF (photon output)
- 65.6 umol/s (source)
- PPFD
- 265.58 umol/m2/s at 1 ft (source)
- Spectrum
- 4000 K, 400-780 nm, CRI close to 100 (source)
- Rated life
- 25,000 hours (source)
Our arithmetic
- Efficacy, computed from the published figures: 1.82 umol/J
65.6 umol/s / 36 W = 1.82 umol/J. That is roughly a third less efficient than the panels on this page — the price of a screw-in form factor. - Electricity used at 12 hours a day for 30 days: 12.96 kWh a month
36 W x 12 h x 30 d / 1000 = 12.96 kWh.
What SANSI does not publish
- Beam angle
- Fixture dimensions
Who should skip it
Skip it if you are lighting more than one plant. 65.6 umol/s is a small amount of light spread over a cone — it lights a single specimen, not a shelf.
Questions people actually ask
+What is a good µmol/J for a grow light?
+Which grow light is most efficient?
+How much does efficacy actually save me?
+Why do some fixtures not publish efficacy?
Sources
- VIVOSUN — VS1000 product page — consulted September 2, 2026
- AC Infinity — IONBOARD S22 published specifications — consulted September 2, 2026
- Spider Farmer — SF1000 published specification table — consulted September 2, 2026
- Mars Hydro — TS 1000 published specification table — consulted September 2, 2026
- SANSI — BR30 36W grow light bulb product page — consulted September 2, 2026
- Soltech — Aspect Gen 2 published specifications — consulted September 2, 2026
- Barrina — T5 ML20 4ft 20W product page — consulted September 2, 2026
- ViparSpectra — P1000 product page — consulted September 2, 2026
- US Energy Information Administration — Electric Power Monthly, Table 5.3 (US residential average, June 2026) — consulted September 2, 2026
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Where this sits
This page belongs to Running Cost and Efficiency. Every figure on it is either quoted from a named published source or derived in view — the full method is on our methodology page, and how the site is funded is on the affiliate disclosure.