Educational · 6 min read
How Much Does a Grow Light Cost to Run? (2026 Data)
A 100-watt LED grow light running 16 hours a day costs $8.66 a month at the April 2026 US average rate of 18.05 cents per kWh. Scale to a 200-watt panel and it doubles to $17.33. Run four 200-watt panels for a full grow tent and the electricity hits $69 a month. Grow lights are one of the few household appliances where the wattage on the label translates directly to a real line item on the electric bill, because the runtime is extreme: 12 to 18 hours a day, every day, for months at a time.
What a single grow light costs per month
The math is watts times hours times rate. A 100-watt LED panel on a 16-hour seedling schedule uses 1.6 kWh per day, 48 kWh per month, and costs $8.66 at the US average rate from the EIA Electric Power Monthly. Switch to a 12-hour flowering cycle and the same light drops to 36 kWh and $6.50 a month. Push to an 18-hour vegetative schedule and it climbs to 54 kWh and $9.75.
Annual costs at 100 watts: $79 on a flowering cycle, $105 for seedling starts, $119 on a full vegetative schedule. Every hour you add to the daily photoperiod on a 100-watt light adds $0.54 a month. The schedule is the biggest lever after wattage.
Tip
Runtime is the cost driver
The wattage ladder
Grow lights span a wider wattage range than almost any other home appliance. Monthly costs at 16 hours a day, US average rate: 32 watts (GE Balanced Spectrum supplemental): $2.77. 70 watts (Mars Hydro TS 600): $6.06. 100 watts (Spider Farmer SF-1000): $8.66. 200 watts(full-spectrum 4×4 tent panel): $17.33. 600 watts (commercial LED bar): $51.98.
Legacy HPS fixtures cost far more. A 400-watt HPS on a 12-hour flowering cycle runs $25.99 a month. A 1,000-watt HPS hits $64.98. Those ballasts are the reason older forums and Reddit threads about grow-light bill shock were accurate. A 200-watt LED panel producing equivalent light output to a 400-watt HPS costs $13 a month on the same 12-hour schedule. Switching from HPS to LED saves $156 a year per fixture.
Multiple lights and the grow tent math
Grow lights scale linearly. There's no duty cycle to soften the cost the way a refrigerator compressor cycles off most of the time. Every panel runs at full power for every hour of the photoperiod.
Four 100-watt panels at 16 hours a day: 192 kWh a month, $34.66. Double the wattage per panel and the bill doubles: 384 kWh, $69. At that level, a grow tent competes with what central air conditioning adds to a summer bill. One Reddit user reported a 50% increase on their electric bill after adding grow lights. At four 200-watt panels, the math supports that for any household with a baseline bill under $140.
A timer prevents over-runs. Every extra hour of unnecessary runtime across four 100-watt panels wastes 12 kWh a month and $2.17. Forgetting to shut off for two extra hours a day wastes $4.33 a month. A $20 programmable smart plug pays for itself in under five months at that rate. Plants don't use the extra light. It's pure waste.
Same grow light, different states
A 100-watt panel on a 16-hour schedule uses 48 kWh a month everywhere. The rate is the only variable:
Louisiana (12.44¢/kWh): $5.97. Texas (14.80¢/kWh): $7.10. US average (18.05¢/kWh): $8.66. New York (24.40¢/kWh): $11.71. California (31.01¢/kWh): $14.88. Hawaii (39.79¢/kWh): $19.10.
The spread is 3.2x between the cheapest and most expensive state for the same light on the same schedule. A four-panel 200-watt setup in California runs $119 a month. In Hawaii, it crosses $153. Every state's 2026 residential rate is in the state rates guide.
Where grow lights land on your bill
A single 100-watt LED panel costs $8.66 a month at the US average. That's more per month than a LED strip running all evening, and about 4.4 times what a wifi router costs annually despite sitting in the same corner of the house. Unlike appliances where the real cost hides in standby power, grow lights have no meaningful standby draw. The entire bill comes from active runtime.
For households running multiple panels, grow lights can become a top-five electricity cost behind HVAC, the water heater, the dryer, and the refrigerator. Four 200-watt panels at $69 a month would sit on any list of expensive appliances to run.
The two levers that matter most: switch to LED if you haven't already (a 200-watt LED replaces a 400-watt HPS and saves $13 a month), and run your photoperiod on a timer to prevent extra hours. Both reduce the bill without changing what the plants receive.
If the bill looks higher than expected, grow lights are worth checking before most other appliances. They're easy to overlook in a closet or tent, but at 584 kWh a year per 100-watt panel, they outpace most of what's plugged in around the house. The grow light calculator takes your panel's wattage, daily schedule, and state rate, and returns the monthly and yearly cost. If you're wondering why your electric bill is high, grow lights are one of the appliances that can actually explain it.