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☀️ Solar garden weather station
“I want a weather station in the garden that never needs charging.”
A small board measures temperature, humidity and air pressure every 10–15 minutes, sends the readings over WiFi, and sleeps. A small solar panel keeps its battery topped up, as long as it's sized for the darkest month, not a sunny day.
What to buy
| Part | Why this one | Rough cost |
|---|---|---|
| ESP32 board with a LiPo battery connector | A built-in battery connector and charger keeps the wiring simple. Low sleep current matters here. | $6–15 |
| BME280 sensor board | Temperature, humidity and pressure in one small part. | $4–8 |
| Small solar panel, 5–6 V, 1–3 W | Size it for winter (see below). | $5–12 |
| Solar charger module for LiPo | Charges the battery safely from the panel. Some boards have this built in. | $2–5 |
| LiPo battery, 1000–3000 mAh | Carries it through cloudy days. | $5–12 |
| Weatherproof box and a radiation shield | A shaded, ventilated cover for the sensor. A stack of plant saucers works. | $5–10 |
Prices are rough ranges, not quotes. Check the current price and stock before you order.
What to install
ESPHome has ready-made support for the BME280 and for deep sleep: wake, send the readings to Home Assistant, sleep for 10–15 minutes. Without Home Assistant, a short Arduino sketch can send the readings anywhere that accepts a web request, even a Google Sheet.
Size the solar for winter
A panel's watt rating is for bright sun at the best angle. In a northern winter, a small panel may give a small fraction of that for weeks. Size for your darkest month: the battery should cover several cloudy days in a row, and the panel should refill it on the few good ones. If the battery sinks during your first winter, send readings less often before buying a bigger panel.
Build it in three steps
- Indoors on USB first. Read the BME280 over I²C and send the readings. Check them against a room thermometer.
- Add sleep, then measure. Make it sleep between readings and measure the average current. That number decides the panel and battery size.
- Then solar, then outside. Connect the charger, battery and panel, and run it on a window sill for a few days before it goes into the garden.
What catches people out
- BMP280 sold as BME280. The BMP280 has no humidity sensor, and sellers mix the two up. If humidity reads nothing or nonsense, check the chip marking.
- Sun on the sensor. Direct sun makes it read several degrees too high. Shade it, with air flowing through.
- Don't charge a LiPo below 0 °C. Charging a frozen lithium battery damages it. In cold climates, use a charger with a temperature cut-off (a thermistor input), or keep the battery somewhere warmer.
- WiFi in the garden. Check the signal where the station will stand before you build the box. If it's weak, see the LoRa mailbox guide.
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