Short answer
Almost always, no — nothing is wrong. Solar output swings enormously with the season, the weather, and the angle of the sun, and a New York system in December makes a small fraction of what it makes in June. That's not a fault; it's how the design works, and your system was sized with it in mind.
The useful question isn't "is this month lower than last month?" It's "is this month lower than the same month last year?" That's the comparison that actually tells you something.
Step 1 — Compare against the same month last year
Open the Enphase app or mySolarEdge, switch the view to monthly or yearly, and look at this month next to the same month a year ago.
- Within about 10–15% — that's normal variation. Some years are cloudier than others. Nothing to do.
- Down 25% or more, two months running — worth a look. Keep reading.
- Your system is less than a year old — you don't have a comparison yet. Compare against the estimate in your paperwork instead, and expect the first winter to feel alarming. It usually isn't.
Step 2 — Work through the ordinary explanations
In rough order of how often each one turns out to be the answer:
| Cause | How to tell |
|---|---|
| It's winter | Short days, low sun angle, more cloud. December and January are the floor of the year here — typically a fraction of a June day. Entirely normal. |
| Snow on the panels | Look at the roof. Covered panels produce nothing. See Snow and ice on your solar panels. |
| Trees have grown | The most common real cause of a genuine year-over-year decline. Shade that wasn't there five years ago now clips your mornings or late afternoons. Look at the daily curve — a shading problem shows as a dent at a consistent time of day. |
| A very hot stretch | Panels are slightly less efficient when they're hot. A 95°F July afternoon can produce a little less than a clear 70°F June one. Counter-intuitive but normal. |
| Dirt, pollen, or a dusty season | Usually a small effect in our climate — rain does the cleaning. Heavy spring pollen or nearby construction can matter for a few weeks. |
| You're reading the wrong number | Both apps show production, consumption, and import/export. It's easy to be looking at the wrong one. Make sure you're on production. |
| A panel or two is offline | Check the array view. One dead panel out of twenty-four is roughly a 4% loss — real, but not what a 30% drop looks like. |
Step 3 — Look at the shape of a single sunny day
This is the most useful thing you can do in two minutes. Pick a recent clear day and look at the daily production graph. A healthy day is a smooth arc — rising through the morning, peaking around midday, tapering into the evening.
- A smooth arc, just shorter and lower than summer — that's the season. Nothing wrong.
- A notch or dip at the same time every day — something is shading the array at that hour. A tree, a new neighbouring structure, a chimney.
- A flat top, cut off abruptly — usually normal on the very brightest days; the system is at its designed ceiling.
- Ragged, jumping up and down — passing cloud, most likely. If it happens on a genuinely clear day, tell us.
- Nothing at all — that's a reporting or fault issue, not a production question. Start with My system stopped reporting.
"My bill went up, so the solar must not be working"
These are two different questions, and it's worth separating them. Your bill is affected by things that have nothing to do with your panels: utility rate changes, delivery charges, a new EV or heat pump in the house, a hot summer running the air conditioning, or where you are in your net-metering cycle.
The way to check the solar specifically is to look at production in the app, not at the dollar figure on the bill. If production is normal for the season and the bill still surprises you, that's a billing question — see Is my solar actually working? Reading your bill.
When to call us
Get in touch if:
- Production is down 25% or more against the same period last year, for two months or more
- You can see a consistent daily dip that wasn't there before
- Several panels are showing zero on the array view
- Production dropped sharply on a specific date rather than drifting down — that usually points to a real event
Tell us what you're comparing against and roughly when it changed. We can pull your system's history from our end and confirm whether it's the weather or something we need to come and look at — and most of the time we can answer that without a visit.
Still stuck? We're here.
Upstate: (518) 478-8365 · Hudson Valley: (845) 681-4088 · info@kasselmansolar.com
Submit a service request online — and if you have your Site ID handy, include it. It lets us pull up your system before we call you back, which usually saves a round trip.
How soon will someone come out? When a visit is needed, we're typically scheduling about two weeks out. That's a typical case rather than a promise — how far you are from us, how full the schedule is that month, and whether a part has to come from Enphase or SolarEdge all move it. If something is urgent or unsafe, tell us when you get in touch and we'll treat it differently.
Last verified: August 2026