Growing Microgreens in Winter: Light, Cold Corners and Electricity Cost per Harvest
The two winter problems
- Not enough light: in a typical northern hemisphere winter, even a south window delivers fewer usable sun-hours; microgreens stretch and lodge without supplementation.
- Cold corners: trays on a north wall or next to an exterior door drop below 15–18 °C, germination stalls, and the medium stays wet longer (mold risk up).
The setup that works in winter
- Move the rack off cold surfaces: interior wall, away from windows/doors; keep the zone 18–24 °C.
- Add light: one clip LED per tray (or a panel over two trays), 12 h on / 12 h off on a timer — see LED lighting guide.
- Airflow: small fan across the rack for a few hours daily; winter rooms are dry, which actually helps mold control.
What it costs in electricity (per month, ballpark)
| Setup | Power draw | 12 h/day energy | ~30-day cost @ $0.17/kWh |
|---|---|---|---|
| One 10–20 W clip over 1 tray | ~15 W | ~180 Wh/day → ~5.4 kWh/mo | ~$0.90 — negligible |
| 30–40 W panel over a 2-tray row | ~35 W | ~420 Wh/day → ~12.6 kWh/mo | ~$2.10 — small |
| 60 W panel, full 4-tray grid | ~60 W | ~720 Wh/day → ~21.6 kWh/mo | ~$3.70 — still small |
The light is not the expensive part. Seed + medium (~$2–4/tray) and your time dominate. The real winter cost is a failed stretch-and-lodge batch you can't eat — which the light investment prevents.
Honest expectations
- Yield per tray in winter ≈ same as summer (radish ~7 days, broccoli ~8–9) if you control light and temperature — winter is a manageable season, not a bad one.
- If you skip the LED, expect a 30–50% stretch rate and lower usable yield in January–February on a north/east window. Budget for it or add the light.
Sources
- Cornell/Utah State extension microgreen guides (temperature and photoperiod ranges).
- Retail LED wattage specs (clip/panel), checked 01.10.2026.