Grow Light Electricity Cost Calculator
Four inputs, one multiplication. Put your own tariff in — the default is a national average and almost nobody pays exactly the average.
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 |  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. | Most light per watt | 2.7 umol/J | |
| 2 |  Barrina T5 4ft Grow Light Strips The default seed-starting bar for good reasons — 4 ft long, linkable in series, cheap per foot — and the reason we built a coverage calculator, because Barrina publishes no photon data whatsoever. | Lowest draw per strip | Not published | |
| 3 |  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. | 36 W total | 1.82 umol/J (ours) |
The reasoning
Grow light running cost is one of the few things in this category with a genuinely exact answer. It is a multiplication, the inputs are all on your fixture and your utility bill, and there is no modeling involved. Anyone telling you a grow light will “spike your bill” without doing this sum is guessing.
Running-cost calculator
Use actual draw, not the “equivalent” figure on the box.
It is on your utility bill. The default is the US residential average.
Five is roughly November through March.
Cost per month
$11.55
Per day
$0.39
Whole season
$57.77
Your arithmetic
150 W × 14 h ÷ 1000 = 2.10 kWh a day.
2.10 × 30 = 63.0 kWh a month.
63.0 kWh × $0.18 = $11.55 a month.
$11.55 × 5 months = $57.77.
The formula
Cost per month = kWh × your rate per kWh
Season cost = cost per month × months
The 1000 converts watt-hours to kilowatt-hours. That is the whole calculation. The only figure that needs care is the rate, and it is the one the calculator defaults for you.
About the default rate
The calculator opens at 18.34 cents per kWh, the US residential average from the Energy Information Administration’s Electric Power Monthly, table 5.3, for June 2026. It is a national average, and the spread between states is wide enough that using it for your own decision is a mistake if you can help it.
Your actual rate is on your bill. Divide the total by the kWh used and you get your effective rate including fees, which is more useful than the headline energy rate on the tariff sheet. If your utility bills you on time-of-use, note the overnight rate too — a grow light is one of the easiest loads in a house to shift.
Per kWh — US residential average, EIA Electric Power Monthly table 5.3, June 2026. Replace it with your own rate; the whole point of the tool is that you can.
A worked example
Mars Hydro publishes 150 W rated power for the TS 1000.
150 × 14 h ÷ 1000 = 2.1 kWh a day.
2.1 × 30 = 63.0 kWh a month.
63.0 × $0.1834 = $11.56 a month.
Across five months: 315 kWh, or $57.77 for the season. Run it at 50% dim instead and both numbers roughly halve.
What people get wrong
- Using the “equivalent” wattage. A fixture advertised as “equal to a 250 W HPS” may draw 100 W. Billing is on actual draw. Use the rated power figure, not the comparison.
- Forgetting the fixture is dimmed. A panel run at 50% draws roughly half. If you dim, the number in the calculator should reflect it.
- Counting a linked string as one fixture. Eight linked Barrina strips at 20 W each are 160 W, not 20.
- Assuming standby draw matters. It does not, at this scale. A fixture that is off is not the reason your bill moved.
The scale of the answer
For nearly every home setup the answer lands somewhere between a few dollars and about thirty dollars a month. That is smaller than most people expect and worth internalizing before you shop, because it changes what you should optimize for: at these numbers, buying the fixture that covers your shelf properly matters far more than buying the one that saves nine dollars a season.
The exception is a large multi-shelf setup run long hours, which is covered in the cost to run a grow light all winter. And if you want to reduce it, efficacy is the lever: the most efficient grow lights by µmol/J ranks the field on exactly that.
Every pick in full
AC Infinity IONBOARD S22
LED panelMost light per watt
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.
Barrina T5 4ft Grow Light Strips
LED barLowest draw per strip
The default seed-starting bar for good reasons — 4 ft long, linkable in series, cheap per foot — and the reason we built a coverage calculator, because Barrina publishes no photon data whatsoever.
What Barrina publishes
- Power draw
- 20 W per fixture; an 8-pack draws 160 W (source)
- Spectrum
- 5000 K (source)
- Dimming
- No; on/off switch per fixture, linkable up to 8 in series (source)
- Dimensions
- 4 ft strip, 120-degree beam angle, 120 V AC (source)
What Barrina does not publish
- PPF in umol/s — for any strip in the range
- PPFD at any stated distance
- Photon efficacy in umol/J
- LED count per strip, and rated lifespan
Who should skip it
Skip it if you need to know what you are getting before it arrives. There is no published PPF, no PPFD and no efficacy figure, so nothing about its output can be verified in advance.
SANSI 36W BR30 Grow Light Bulb
Grow bulb36 W total
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
+How do I calculate what my grow light costs to run?
+What electricity rate should I use?
+Do LED grow lights use a lot of electricity?
+Should I use the actual wattage or the equivalent wattage?
Sources
- US Energy Information Administration — Electric Power Monthly, Table 5.3 (US residential average, June 2026) — consulted September 2, 2026
- ViparSpectra — P1000 product page — consulted September 2, 2026
- Barrina — T5 ML20 4ft 20W product page — consulted September 2, 2026
- Mars Hydro — TS 1000 published specification table — consulted September 2, 2026
Read next
Running Cost
How Much Electricity Do Grow Lights Use?
Monthly kWh and cost per fixture, and how that compares with household appliances.
Running Cost
The Cost to Run a Grow Light All Winter
Five setups priced for a full winter season, from a clip light to a three-shelf rack.
Running Cost
The Most Efficient Grow Lights by µmol/J
Every fixture we cover ranked on published photon efficacy, with derivations shown.
Coverage & Sizing
Grow Light Coverage Calculator
Put in PPF, area and hours; get PPFD and DLI scored against published extension bands.
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.