Is My Solar System Working? How to Check Your Production
To check whether your solar system is working, compare how many kWh it actually produced with how many it should have produced for your location, size and roof. Over a full year, being within about 10% to 15% of a good estimate is normal. Over a single month, weather can push you well above or below, so compare the same month year to year. A drop to zero almost always means the inverter or a breaker is off; a steady partial shortfall points to a component failure, new shading or a design issue.
Step 1: find your actual production
You have up to four places to look:
- Monitoring app or website. Enphase, SolarEdge, Tesla and most other inverter makers offer an owner app that shows daily, monthly and lifetime kWh. If your installer set it up under its own account and you can’t log in, contact the manufacturer for homeowner access.
- Inverter display. Many string inverters show current output (kW) and lifetime energy (kWh) on a small screen or status light.
- Production meter. Some systems, especially those in incentive programs, have a separate revenue-grade meter that counts total kWh produced.
- Utility bill. It shows kWh you exported, not total production. Power you used directly in the house never reaches the meter. Exports are useful as a sanity check: if they’re zero on a sunny month, something’s wrong.
Write down your monthly production for the past 12 months if you can.
Step 2: get an expected production estimate
You need a fair yardstick. Options, from best to quickest:
- Our production checker. Enter your location, system size, tilt and direction. It uses PVWatts-style modeling, the free tool from the National Laboratory of the Rockies (formerly NREL).
- PVWatts directly. Search “PVWatts calculator.” It models typical-year weather and includes default system losses of about 14% for soiling, shading, wiring, mismatch and similar effects.
- Your installer’s proposal. It should list expected first-year kWh. Be cautious: some sales proposals overstate production. See inflated production estimates.
As a very rough national guide, each kW of panels typically makes somewhere around 1,100 to 1,700 kWh a year depending on location and orientation. A 7.7 kW system, the 2025 U.S. median size according to Lawrence Berkeley National Laboratory, might produce roughly 8,500 to 13,000 kWh a year. Use a location-specific estimate rather than this range for any real comparison.
Step 3: compare fairly
| Comparison | How to read it |
|---|---|
| Full year vs annual estimate | Within about ±10% to 15% is normal. A typical-year estimate won’t match an unusually cloudy or sunny year |
| Same month, this year vs last year | Best test for a new problem; adjust for panel aging of about 0.5% a year |
| One month vs that month’s estimate | Weather alone can swing a month by 20% or more |
| Today vs yesterday | Mostly tells you about clouds |
Panel aging. Studies of real systems find a median output loss of about 0.5% a year, with fleet averages closer to 0.75% a year and higher losses in hot climates. After 10 years, a system losing 0.5% a year would produce about 95% of what it did at first. If you’re down 15% after three years, that’s not aging. See solar panel lifespan and warranties.
Seasonal variation is normal
Production follows the sun. Shorter days, a lower sun angle, clouds and snow all reduce winter output, while long summer days boost it. The swing is bigger the farther north you are. In many northern locations, a December can produce a third or less of a June. In the Southwest the difference is smaller.
Very hot weather also trims output slightly. Panels lose a fraction of a percent of power for each degree Celsius they heat up. Modern panels typically lose about 0.25% to 0.37% per degree, depending on the cell technology. That’s why a clear, cool spring day can beat a hot July afternoon.
Common problems and what they look like
The whole system shows zero
Likely causes, in rough order:
- The inverter shut off after a grid outage and didn’t restart. Many restart automatically; some need a manual restart.
- A tripped breaker in your main panel, or a solar disconnect switch turned off (sometimes by a roofer, electrician or utility worker).
- Inverter failure. String inverters commonly last 10 to 15 years. Replacing one typically costs around $1,500 to $3,000.
- Monitoring is down but the system is fine. A changed Wi-Fi password or a new router often breaks the data connection. Check the inverter’s own display or your utility exports before assuming the worst.
Production dropped partway
- Failed microinverters or optimizers. Panel-level systems keep running when one unit fails, so you might lose 5% to 10% without noticing. Panel-level monitoring will show which panels are dark. See microinverters vs string inverters.
- New shading from a growing tree, a neighbor’s addition, or a satellite dish.
- A damaged panel or wiring fault, such as a loose connector, chewed wires from squirrels or rodents, or hail or storm damage. See solar weather, durability and insurance.
- Heavy soiling in dusty, dry areas with little rain, or from bird droppings and pollen. Most homes don’t need regular cleaning; PVWatts assumes about 2% average soiling loss.
- Export limits or “clipping.” If your inverter is smaller than your panel array, output flattens at the inverter’s maximum on bright days. Some clipping is a normal design choice, not a fault.
Production was never as high as promised
If your first full year fell well short of the proposal and your system shows no faults, the estimate was probably optimistic. Compare the proposal to a PVWatts estimate with your real roof direction and shading. If you have a production guarantee, check its terms and file a claim if you qualify. See weak production guarantees.
Common inverter error types
Exact codes vary by brand, so check the manual or the manufacturer’s support site. The usual families:
| Error type | What it means | What to do |
|---|---|---|
| Grid fault (voltage or frequency out of range) | The utility grid was outside allowed limits, so the inverter disconnected for safety | Often clears by itself; if frequent, the utility or installer may need to check voltage |
| Ground fault or isolation fault | Current is leaking somewhere it shouldn’t, often from damaged insulation or moisture | Don’t keep resetting; call a qualified technician |
| Arc fault | The inverter detected arcing, which can come from a loose or damaged connection | Treat as a safety issue; call a technician |
| Communication or “not reporting” | The device isn’t sending data | Check Wi-Fi, router and gateway power first |
| Overtemperature | The inverter is too hot, often from direct sun or poor ventilation | Check that vents aren’t blocked; ask about shading the unit |
Watch out: Never open an inverter, junction box or combiner, or walk on the array to inspect it. Solar panels produce dangerous DC voltage whenever there’s light, even when the breaker is off. Use the manufacturer’s shutdown steps and leave the rest to a licensed professional.
A simple monthly routine
Five minutes a month catches most problems early:
- Open the monitoring app and note last month’s kWh.
- Compare it to the same month last year or to your estimate.
- If you have panel-level monitoring, scan for any panel showing much less than its neighbors.
- Check your utility bill for exported kWh and the export credit.
- Every spring and fall, look at the array from the ground for debris, damage, sagging wires or new shade.
If you don’t have monitoring at all, a home energy monitor can track production and household use; see cheaper first steps for options.
Who to call
- Installer still in business: start with them, especially if you’re within the workmanship warranty.
- Installer gone: use the inverter manufacturer’s warranty process and an independent servicer. See what to do if your solar company went out of business.
- Leased or PPA system: the system owner is usually responsible for repairs. Call the company that bills you.
- System fine but bill still high: see why is my electric bill still high with solar?.
- New system not producing at all: check whether you have Permission to Operate yet. See interconnection and PTO.
If you’re planning to add panels or wondering whether your system is the right size for your usage now, try the system size calculator.
Common questions
How do I know if my solar panels are working without an app?
Look at the inverter's display or status light in daylight, which usually shows current output or a fault. You can also check your utility bill or online account for exported kWh, or read your production meter if you have one. If all show zero on a sunny day, the system is probably off.
How much should my solar panels produce?
It depends on system size, location, roof direction, tilt and shading. Across the U.S., each kW of panels typically produces somewhere around 1,100 to 1,700 kWh a year, more in sunny southern and western states and less in cloudy northern ones. Use a PVWatts-based estimate for your address to get a number for your system.
Why is my solar production lower in winter?
The sun is lower, days are shorter, and snow or clouds block more light. In many northern locations, a December month can produce a third or less of a June month. That's normal and is built into annual production estimates.
Should I reset my solar inverter?
A simple power cycle following the manufacturer's shutdown procedure can clear some faults, such as after a grid outage. If the same error returns, or you see ground fault or arc fault messages, stop resetting and call a qualified technician, because those can indicate a wiring problem.
Spotted an error or outdated number? Email hello@unbiasedsolar.com and we'll fix it. No installer or lender paid for or reviewed this guide.