Find the right grow light wattage and estimate electricity costs for your indoor garden
32 W/sqft x 16.0 sq ft
200W each (600W total)
9.60 kWh/day
at $0.12/kWh
estimated 30-day period
| Plant Type | LED W/sqft | HPS W/sqft | Hours/Day |
|---|---|---|---|
| Leafy Greens | 20 | 30 | 12 |
| Herbs | 25 | 35 | 14 |
| Tomatoes & Peppers | 32 | 50 | 16 |
| Flowering Plants | 35 | 55 | 12 |
| Seedlings | 15 | 20 | 16 |
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Result
A 4x4 LED tomato setup needs 512W (3 fixtures at 200W each = 600W actual), costing about $34.56/month.
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Result
An herb garden under fluorescent lights needs 240W (5 tubes at 54W each = 270W actual).
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Result
A 5x5 HPS flowering room needs 1,375W (3 fixtures at 600W each = 1,800W actual), costing $97.20/month.
It depends on the plant type and light technology. LED lights need 20-35 watts per square foot, while HPS lights need 30-55 watts. Leafy greens need less light (20W/sqft LED) than flowering plants like tomatoes (32W/sqft LED).
Yes, LED grow lights are significantly more efficient. They produce more usable light per watt, generate less heat, and last 50,000+ hours versus 10,000 for HPS. While LEDs cost more upfront, they save 30-50% on electricity over time.
Most vegetables and flowering plants need 12-16 hours of light daily. Leafy greens and herbs thrive with 12-14 hours, while tomatoes and peppers prefer 16 hours. Seedlings also benefit from 16 hours to promote strong growth.
Running costs depend on wattage and electricity rate. A typical 4x4 ft LED setup (two 200W fixtures) running 16 hours daily costs about $1.15/day or $35/month at $0.12/kWh. HPS setups cost 50-80% more due to higher wattage requirements.
LED lights should be 12-24 inches above plants, HPS lights 24-36 inches, and fluorescent lights 6-12 inches. Start higher and lower gradually. Watch for light burn (bleached leaves) or stretching (light too far away).
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Last Updated: Feb 12, 2026
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