Indoor cannabis cultivation offers growers complete environmental control, but it also requires multiple electrical devices for lighting, ventilation, and climate control.
Understanding how to estimate your energy use is essential to avoid unexpected costs and to plan a grow that fits your budget.
While setups vary widely, the basic process for calculating your energy needs is always the same: identify which devices consume power, for how long they run, and convert this into kilowatt-hours (kWh).
The Main Sources of Electricity Use
Every indoor grow requires several components that run for long periods. The most common power-consuming tools include:
- Grow lights (HPS, LED, CMH, etc.)
- Ballasts or drivers for lighting
- Extractor fan for ventilation
- Oscillating fan for air circulation
- Optional systems: heaters, AC units, dehumidifiers, and humidifiers
Lighting is usually the most significant component of the energy bill. Many traditional grow lights range from 150W to 1000W, with 400W often considered a basic starting point for a small setup. Ventilation and fans use far less electricity but run continuously.
How to Calculate Electricity Consumption
Electricity costs are calculated in kilowatt-hours (kWh). One kilowatt equals 1000 watts. The formula is straightforward:
(Wattage × Hours of use) ÷ 1000 = kWh
Once you have kWh, you multiply the result by your electricity price per kWh.
Example:
Let’s imagine a simple growing tent with:
- One 400W grow light
- A ballast that adds about 15% extra consumption
- An extractor fan (around 30W)
- An air-circulation fan (around 20W)
A typical grow lasts around 12 weeks, with 4 weeks of vegetative light and 8 weeks of flowering.
Lighting usage:
- Vegetative stage: 18 hours a day
- Flower stage: 12 hours a day
By multiplying watts × hours × days, you can add up the total watt-hours for each device. Converting this total into kWh gives you a realistic estimate of how much energy the grow will use from start to finish. After that, you multiply by the energy rate in your area.
The exact numbers will vary depending on local electricity prices, equipment efficiency, and any additional climate-control tools. Modern LEDs, for instance, can significantly reduce consumption compared to high-pressure sodium lamps.
What Influences Your Final Electricity Costs?
Several factors can increase or reduce your spending:
- Light type and efficiency
- Grow size and number of devices
- How long each growth stage lasts
- Ventilation strength and airflow needs
- Your chosen light schedule
Even two identical tents may have different power consumption if one grower uses extra heaters or longer lighting cycles.
Using Your Estimates for Future Grows
Once you calculate energy costs for one indoor cannabis grow, the process becomes easier. You can adjust equipment or schedules to fit your budget. Switching to more efficient components or running fewer devices for fewer hours can also lower your long-term costs.
These calculations give you a baseline. From there, you can scale up or down depending on the size of your next cultivation.