Solar Panel Output on a Short Fall Day

People buy a solar panel for the fall camping trip and are surprised when it barely charges the power station. It's not broken. It's October.

01Why output drops in fall

• Shorter days. Fewer hours of daylight.
• Lower sun. The sun sits lower in the sky, so its light comes through more atmosphere and hits the panel at an angle.
• Shade. Low sun means longer shadows from trees, the RV, and hills.
• Clouds and rain come more often in many places.

02A planning number

Panels are rated in watts under perfect lab conditions. In the real world, you rarely get the full rating.

A rough way to plan: take the panel's rating, assume you'll get maybe 60 to 75 percent of it in good sun, and multiply by "peak sun hours" (the equivalent hours of full sun in a day). In much of the country, late fall gives roughly 2 to 4 peak sun hours on a clear day, less in the north and more in the Southwest.

Example

200-watt panel × 70 percent × 3 hours = about 420 Wh on a good fall day.

That might cover a fridge and phones. It won't fully recharge a big power station.

03Getting the most out of it

• Aim it at the sun. Tilt it more upright in fall, and turn it a few times a day to follow the sun.
• Get it out of the shade, even partial shade. A shadow on one corner can cut output a lot.
• Use a longer cable so the panel can sit in the sun while the station sits in the shade.
• Start early. Set it up as soon as the sun clears the trees.
• Keep it clean. Leaves and dust cost you.

04Have a backup

• Charge from the car while you drive.
• Bring the generator if the campground allows it. See generator quiet hours.
• Cut what you use. See a power station for a CPAP.

Solar is great in fall. Just plan on less of it.

Photo by mrganso on Pixabay.

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