Leaves on Solar Panels: A Connecticut Fall Guide

Leaves on solar panels cost more power than they look like they should, because shading even part of one cell can switch off a whole section of a panel. In Connecticut the practical plan is simple: don’t climb up to clear them, let the trees finish dropping, then have the panels cleaned once in late November or early December, before winter. Wooded towns and the shoreline run on slightly different calendars, and both are covered below.

Do leaves on solar panels really reduce output?

Yes, and by more than the covered area suggests. A panel’s cells are wired together in groups, each protected by a bypass diode. When one cell is shaded, the diode can switch off its whole group so the rest of the panel keeps working. Research from the National Renewable Energy Laboratory found that on typical silicon panels, cutting a single cell’s light by just 25% can be enough to trip that diode.

So a few maple leaves stuck along the bottom row are not a cosmetic problem. They can take a noticeable bite out of a sunny October afternoon, at the time of year when the days are already getting shorter.

When do the leaves come down in Connecticut?

The state forestry division puts Connecticut’s foliage season from late September into early November, with peak color estimated between October 3 and November 8. The order is predictable. The northern hills change first and the shoreline last, according to CTvisit’s foliage finder, which is built on field observations by state foresters. Leaves keep falling for weeks after peak color.

For the towns we serve, that means:

• Wooded inland towns, including Woodbridge, Bethany, Cheshire, Durham and Easton, get the heaviest leaf load. Oaks here also drop acorns and hold some leaves well into November.
• Shoreline towns, including Branford, Guilford, Madison and Westport, color and drop later. Salt air adds its own film to the glass through the season.

Should you blow or rake leaves off your panels?

No. Stay off the roof. Wet October leaves make shingles slick, and a fall from a roof is far more expensive than any lost production. Rakes, brooms and metal tools can scratch the glass, and a pressure washer can force water past seals. Dry leaves on a tilted array often blow clear on their own in the next breeze.

What doesn’t clear itself is the mat of wet leaves that collects along the bottom edge and under the panels. It holds moisture against the frame and turns into grime as it breaks down. That is a job for a proper cleaning, not a ladder.

What about acorns and the space under the panels?

Fall is also when squirrels are busiest. The gap between the panels and the roof collects leaves and acorns, and that sheltered, cushioned space is exactly what a squirrel looks for before winter. If you hear scratching or see nesting material poking out, read our guide to squirrels under solar panels in Connecticut. A critter guard closes that gap for good. The best time to install one is right after the space has been cleaned out.

When should you book a fall cleaning in Connecticut?

After the leaves are down, which for most of our towns means late November or early December. Cleaning at the peak of leaf drop just means the panels collect a new layer the following week. This is the same fall visit we recommend in our guide to how often to clean solar panels in Connecticut. The other visit is in late spring, after pollen.

A residential cleaning uses deionized water and soft brushes, with no pressure. It clears the leaf film, the wet debris along the bottom edge, and the season’s grime, so the panels go into the short winter days as clean as they can be. And if you’re waiting on rain to do the job, it won’t. Here’s why rain doesn’t clean solar panels.

If your panels sit under oaks or maples, or you’d like a look at what fall has left on them, call or text (203) 659-0781 and we’ll schedule a visit once your trees are bare.