SOLAR GREENHOUSE

200W Monocrystalline Solar Panel

Mounts on the greenhouse roof or nearby post. 200W is enough for fans, lights, and monitoring. Renogy and Newpowa make panels sized perfectly for greenhouse roofs.

MPPT Charge Controller (20A)

Handles the higher voltage from a 200W panel efficiently. The Renogy Rover 20A or EPEVER Tracer 20A both work. MPPT matters here because greenhouse panels often get partial shade from the structure.

12V 50Ah LiFePO4 Battery

Stores enough to run fans and lights overnight or through cloudy days. LiFePO4 handles the heat inside a greenhouse far better than lead-acid. The LiTime 12V 50Ah is a popular choice at this size.

12V Ventilation Fans (x2)

Temperature control is the #1 job. Two 12V inline duct fans — one low for intake, one high for exhaust — create airflow that keeps plants alive in summer. Thermostat-controlled fans only run when temp exceeds your setpoint.

12V LED Grow Light Strips

Supplement winter daylight for year-round growing. Full-spectrum LED strips on timers extend the growing season by weeks. Low draw — a few strips run all day on minimal power.

Automatic Vent Opener (Heat-Activated)

No power needed — these use wax cylinders that expand with heat. Install on roof vents for passive ventilation backup. Univent and Gigavent are the standard brands.

Temperature & Humidity Monitor (WiFi)

A WiFi-connected sensor lets you check conditions from your phone. The Govee or SensorPush models are waterproof and run for months on a single battery.

Heated Water Reservoir / Mat (Optional, Winter)

A small submersible heater in a water barrel creates thermal mass that stabilizes nighttime temps. Alternatively, a seedling heat mat powers from the 12V system through a small inverter.

Wiring: 12 AWG Wire, Connectors, Fuse Block

Slightly heavier gauge than the chicken coop build to handle the fan motors. A small fuse block keeps everything organized. Waterproof connectors are essential in a humid greenhouse.

Mount the Solar Panel

Attach the 200W panel to the greenhouse roof ridge or on a post beside the greenhouse. South-facing, angled for your latitude. Run MC4 cables through a sealed entry point into the greenhouse's utility area — a shelf, corner, or small weatherproof box near the door.

Set Up Battery and Controller

Mount the charge controller on the interior wall. Connect the battery to the controller's battery terminals, then connect the solar panel. Place the LiFePO4 battery off the ground on a shelf — greenhouses get humid, and moisture pooling is the enemy. A waterproof container or bag adds protection.

Install Ventilation Fans

Mount the intake fan low on one end wall, and the exhaust fan high on the opposite end wall. This creates cross-ventilation that mimics natural airflow. Wire both through a 12V thermostat controller set to activate at 85°F (adjustable). Connect to the charge controller's load terminals or directly to the battery through the fuse block.

Add Grow Lights and Timers

Mount LED grow strips along the ridge beam or on horizontal supports above your growing tables. Wire through a 12V timer — set to extend daylight to 14–16 hours during winter months. In summer, the timer can be off entirely. Total draw is minimal — a few watts per strip.

Install Monitoring and Passive Systems

Place the WiFi temperature/humidity sensor centrally, at plant height. Install automatic wax-cylinder vent openers on the roof vents as backup ventilation. If using a heated water reservoir, fill a 5-gallon barrel with water and place the submersible heater inside — set to maintain 50°F minimum. The thermal mass alone helps stabilize overnight temps.

Test and Tune

Run the system for a full day/night cycle. Check that fans kick on at your target temperature and shut off when it cools. Verify grow lights follow the timer schedule. Monitor battery level overnight — you should have plenty of margin with 50Ah. Adjust thermostat setpoints and timer schedules by season.