A Solar Camera's Winter Problem Is Arithmetic, Not Hardware

Solar cameras are returned in February more often than in any other month, and the returns are rarely faulty. The pattern is always the same: it worked from April to October, went flat in December, and by January it was offline. Nothing broke. The energy budget stopped balancing, and it was always going to.

The only number that matters is not the one printed largest

A panel is sold on peak watts, measured in the lab — full sun, perpendicular, cool cells. None of those hold on a wall in winter.

What matters is equivalent full-sun hours per day, which varies by latitude, season and orientation:

• Summer, mid-latitudes, panel tilted toward the equator: four to six hours.
• Winter, same location: one to two hours on a clear day, less on an overcast week.

That is a factor of three to four between best and worst month, and it is the entire story. A system sized to just barely work in summer fails in winter by roughly the factor it was oversized by.

Where the energy goes

The consumption side is dominated by three things, and the third is the one nobody accounts for:

1. Radio wake-ups. The camera sleeps and wakes on motion; each wake-up costs a burst — processor up, radio association, upload. Twenty to forty a day is ordinary for a front path, and each costs a fixed amount regardless of recording length.
2. Night-time infrared. After dark the camera runs LED illumination and a harder exposure, and gets nothing from the panel. Every night is a withdrawal with no deposit.
3. Motor current, if it is a PTZ. A pan-tilt motor on a small battery is a pulsed load: several times running current for the second or two it takes to move, usually during a tracking sweep — exactly when the camera is also awake, streaming, and possibly running infrared.

Why solar and PTZ is the hardest combination

A fixed solar camera has a modest, predictable load. A solar PTZ has the same base load plus large pulses, arriving at the worst possible moment.

Battery internal resistance rises as the cells get cold. A cold battery is worse at delivering a current pulse than a warm one at the same state of charge. So on a cold winter evening: the panel has delivered almost nothing all day, the battery is cold and depleted, infrared comes on, the camera detects motion, and the motor demands a pulse the battery cannot supply. Voltage sags, the processor browns out, the camera reboots — then tries again and sags again.

It looks like a firmware crash. It is a power supply collapse, and rebooting makes it worse, because each reboot costs another wake-up cycle.

If you want a PTZ, the honest recommendation is mains or Power over Ethernet. If it must be solar, oversize the battery and expect to lose tracking on the coldest weeks.

The arithmetic, done once

• Daily income = panel watts × equivalent full-sun hours × derating. The derating covers non-perpendicular mounting, dust, controller efficiency and panel heating. Use 0.5 to 0.6.
• Daily spend = standby × 24h + wake-ups × cost per wake-up + night hours × night draw.
• The gap is what the battery covers every day, and in winter it must cover a run of overcast days, not just one.

If December income is below spend, no battery size saves you permanently — a bigger one only lengthens the time before it goes flat. The fix is a larger or better-sited panel, or fewer wake-ups.

Reducing the spend is easier than increasing the income

• Cut wake-ups, not recording length. The fixed cost of a wake-up is what you are paying. Lowering sensitivity, narrowing the detection zone, and excluding a road or pavement can halve events without changing what you capture at the door.
• Turn off what you are not using. Status lights, continuous recording and always-on streaming are continuous loads on a device designed to operate intermittently.
• Reduce infrared cost if the scene is lit. With a porch or street light, the camera may not need its illuminators at full power.

Siting beats specification

Given the choice between a larger panel in a poor position and a smaller one in a good position, take the position:

• Face the equator. North-facing in the northern hemisphere, south-facing in the southern. A panel facing away from the sun is close to decorative in winter.
• Tilt it roughly to your latitude rather than mounting it vertical. Vertical is convenient on a wall and loses a large fraction of winter output.
• Separate the panel from the camera if you can. The best angle for seeing a doorway is often the worst for catching sun, and a short lead lets you optimise each independently.
• Keep it clean and reachable. A panel you cannot wipe loses output slowly, which makes the loss invisible.

The honest conclusion

A solar camera is a battery camera with a top-up, and it inherits every limitation: event-driven wake-up, no pre-roll, and a power budget that constrains bitrate and infrared. Solar extends the interval between charges; it does not remove the limits.

It is the right answer where running a cable is impossible, where the position gets reasonable sun, and where missing the occasional event in February is acceptable. It is the wrong answer for a position that matters, for a PTZ whose tracking you depend on, and where the best camera angle is also a north wall.

Solar doorbell options are in the U9 solar video doorbell page, and solar PTZ models at the Tuya solar PTZ security camera. The wider range is in the surveillance camera category, with OEM detail at the CCTV camera manufacturing page.