EQUIPMENT · RUNNING COSTS
WHAT A GROW TENT COSTS TO RUN
The math is simple: watts × hours ÷ 1,000 = kWh, then multiply by your electric rate.
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The formula
Monthly cost = (watts × hours per day × 30) ÷ 1,000 × your $/kWh. Find your rate on your utility bill; US averages are roughly $0.15–0.35/kWh, and California is at the high end.
Example: a small gourmet fruiting tent at $0.30/kWh
| Device | Typical watts | Hours/day | kWh/month | Cost/month |
|---|---|---|---|---|
| Humidifier | 40 W | 24 h | 28.8 kWh | $8.64 |
| Small fan | 25 W | 24 h | 18.0 kWh | $5.40 |
| Controller + sensors | 5 W | 24 h | 3.6 kWh | $1.08 |
| LED light | 30 W | 12 h | 10.8 kWh | $3.24 |
| Small heater (cool rooms only) | 400 W | 4 h | 48.0 kWh | $14.40 |
| Total | 109.2 kWh | $32.76 |
How to cut it
- Heat is the big cost. Many gourmets (most oysters) fruit happily at normal room temperature, so skip the heater if you can.
- Put the humidifier and fan on a controller so they only run when needed.
- Lights only need a few hours for most species; use a timer.
- A pressure canner on an electric stove adds roughly 1.5–2 kWh per sterilization run.
- Check the actual draw with a plug-in watt meter. Labels are often maximums.
Example wattages are typical label figures for small consumer devices, not measurements of a specific setup.