Weather stations are commissioned to produce continuous records, and the seasons that matter most for science — winter storms, monsoon, overcast periods — are exactly the seasons that starve a solar supply. Uptime therefore depends less on rated panel wattage than on how the array behaves in diffuse light and how much capacity the battery retains when it is cold.
Rated wattage is measured at conditions that rarely occur
A 200 W panel is rated at 1000 W/m² irradiance and 25 °C cell temperature. On an overcast winter day, irradiance may be 80-150 W/m², and the panel produces a small fraction of its rating. Under those conditions, module technology and controller behaviour matter more than the nameplate:
- Monocrystalline cells generally hold a slightly better low-light response than older poly types of the same vintage
- Half-cut and multi-busbar cell layouts reduce series resistance losses, which helps at low current
- An MPPT controller keeps harvesting as voltage drops; a PWM controller loses proportionally more in weak light
Cold is good for panels and bad for batteries
Panel voltage rises as cell temperature falls, which is why array open-circuit voltage must be checked against the controller’s maximum input at the coldest expected morning — not the datasheet at 25 °C. Batteries behave the opposite way: a lead-acid pack at 0 °C may deliver only 70-80 percent of its rated capacity, and charging below freezing can damage lithium cells without a low-temperature charge cut-off.
For high-latitude or high-altitude weather stations, this means either a heated or insulated battery compartment, a lithium pack with low-temperature charge protection, or simply a larger usable capacity margin than a warm-climate design would use.
Design for the worst month, then add a data-integrity margin
Scientific records do not tolerate a two-day gap, so the autonomy target should exceed the longest expected overcast run, and the array should be sized on the lowest monthly yield with a margin for snow or rime on the glass.
A station drawing 90 Wh/day in a location with 1.8 peak sun hours in December needs an array near (90 x 1.3) / (1.8 x 0.7) = 93 Wp before allowing for snow cover. Practical builds double that, because a partially covered panel in December is a normal condition rather than an exception.
Heating, ventilation and enclosure design
| Condition | Design response |
|---|---|
| Snow and rime | Steeper tilt, smooth frame, panel within reach for clearing |
| High summer temperature | Ventilated enclosure, white or reflective cabinet, controller derating check |
| Humidity and condensation | Gore vent or desiccant, conformal coating on the logger |
| Salt or dust | IP65+ enclosure, sealed connectors, periodic cleaning access |
FAQ
Do solar panels work on cloudy days?
Yes, at roughly 10-25 percent of rated output depending on cloud thickness. The array still charges the battery, but sizing must assume the low end for consecutive days rather than the annual average.
Will a weather station keep logging through winter?
It can, if the array is sized on the December yield, the battery is protected from cold or oversized for the capacity loss, and the panel is mounted where snow can shed or be cleared.
Is a bigger panel always better for a weather station?
Not always. Beyond the controller and cabling limits, an oversized array adds wind load to a mast and can overcharge a small battery. Match array, battery and load as a set.
Send us your station’s sensors, sampling interval and winter sun hours and we will size the supply. Contact the engineering team or see solar power for weather stations.