Grow-light electricity cost calculator
Estimate monthly energy use and cost for a grow light.
Use the result as a starting point.
Enter measured values, check the units, and keep the assumptions beside the answer. This tool supports a growing decision; it does not replace a calibrated meter, a product label, or observation of the crop.
Formula: watts ÷ 1,000 × hours/day × days × rate. Add fans and pumps separately.
How to use this tool
Use this estimate to budget the electricity portion of an indoor grow. Add pumps, fans, and other devices separately.
- Enter equipment watts, hours per day, days in the billing period, and your utility rate in dollars per kWh.
- Enter the values, check the units, and select Calculate.
- Read the result as a planning estimate, then compare it with the crop and system.
Formula or reference method
Energy = watts / 1,000 x hours per day x days. Cost = energy x rate.
Worked example
A 150 W light for 16 hours daily over 30 days uses 72.0 kWh. At $0.16/kWh, the estimate is $11.52.
Understanding the result
The result is an operating estimate for the entered device and schedule, not a full utility bill forecast.
Assumptions and limits
Wall draw can differ from the label because of drivers, power factor, timers, and standby loads.
Common mistakes
Do not enter watts as kilowatts or confuse the utility rate with the monthly bill total.