The clocks just fell back and the sun is setting before dinner. If you have solar panels — or you're thinking about getting them — the same question comes up every November: what happens when the days get short?
Cold Weather Is Actually Good for Solar Panels
Solar panels produce electricity more efficiently in cold temperatures than in hot ones. Panels are rated at 77 degrees Fahrenheit. On a 95-degree July day, when the panel surface hits 150 degrees, you're losing 10% to 15% of rated output to heat alone. On a cold, clear December day at 35 degrees, your panels are running above their rated efficiency.
The panels don't need heat. They need light.
Shorter Days Mean Less Production — But That's by Design
Winter days in SE PA are short — about nine to ten hours of daylight compared to fifteen in June. A system in PECO territory typically produces 55% to 65% of its peak monthly output during December and January.
But your system was designed around annual production, not your best month. The production estimate already has winter baked in.
And because PECO's net metering resets every May 31, the credits you banked during those long sunny days from May through September offset the months when production dips. Your panels overproduce in summer so you can draw on those credits in winter.
What About Snow?
Less of a problem than most people assume. Solar panels are dark, smooth, and angled — light snow melts within hours. After a heavier storm, panels may be covered for a day or two, but SE PA's pattern of cold snaps followed by milder stretches means they clear themselves quickly.
Don't climb on your roof to clear them. The production loss from a day or two of snow cover is minimal over the year, and the safety risk isn't worth it. Snow-related losses typically amount to 2% to 5% of annual output, and your system's model already accounts for this.
Why Your Winter PECO Bill Looks Higher
If your PECO bill creeps up in November, it's not that your panels stopped working. In winter, your panels produce less while your home uses more — more lighting, heat pumps running harder. You draw more from the grid than your panels offset in real time.
That's what your banked net metering credits are for. PECO applies summer credits against winter usage automatically. The goal isn't zero every month — it's zero over the full year, settled at the May 31 true-up.
Two Things to Check Right Now
- Look at your monitoring app. Check whether any panels are consistently underperforming. Lower winter sun angles mean a tree that didn't cause shade in June might be blocking panels now. If you spot the issue, trimming nearby branches is one of the most cost-effective ways to boost winter production.
- Think about your timeline. If you've been considering solar, fall and winter are when installation schedules are most open. Permitting offices aren't backed up, crews are available, and a system that goes live this winter starts banking credits before your air conditioning spikes next July.
The Bottom Line
Your solar panels work in cold weather — they actually work better on cold, clear days than in summer heat. Shorter days and snow mean lower monthly production, but the annual math, net metering, and proper system sizing all account for that.
There's no wrong season to start saving on your electric bill. Get a free estimate or call us at 610-900-6405.
Pennstar Solar has been installing solar panels and battery storage systems across southeastern Pennsylvania since 2013. Learn more about our services.
