What to do if your solar system underperforms

You were told your solar system would produce a certain amount of electricity each year. Maybe it was printed right on the proposal. Now your monitoring app shows numbers far below that, and your utility bill isn't shrinking the way it should.

Underperformance is one of the most common solar complaints, and one of the most fixable when it's caught and documented early. Here's how to approach it step by step.

Step 1: Find the number you were promised

Look for a production estimate in:

• Your proposal or sales presentation (often shown as "estimated annual production" in kilowatt-hours, or kWh)
• Your lease or PPA, which may include a production guarantee
• System design documents or a "site survey" report

Write down the annual estimate, and if available, the month-by-month estimate. Solar production naturally varies by season, so a monthly breakdown is more useful than a single yearly number.

Step 2: Find out what your system actually produces

Most systems come with a monitoring app or web portal from the inverter manufacturer or solar company. Look for:

• Lifetime production and production by year and month
• Any error messages or alerts
• Days with zero production (often a sign of an outage)

If your monitoring has been offline, that's a problem in itself: many production guarantees depend on monitoring data, and you can't see failures without it. Your utility bill may also show how much energy you exported to the grid, which offers another data point.

Take screenshots or export the data. Save it somewhere safe. Some monitoring platforms only keep detailed data for a set period.

Step 3: Compare fairly

A few things are normal and expected:

• Seasonal variation. Production drops in winter and on cloudy or snowy days.
• Weather years. An unusually cloudy year can lower production by several percent.
• Gradual degradation. Panels lose a small amount of output each year, often around half a percent annually for quality panels. Your warranty or contract may specify the expected rate.

A system producing 3% to 5% below estimate in a cloudy year may be fine. A system producing 20%, 30%, or more below estimate, year after year, likely has a problem: in the equipment, in the design, or in the original estimate.

For an independent check, the U.S. Department of Energy offers a free calculator called PVWatts that estimates expected production based on your location, system size, roof direction, and tilt.

Step 4: Identify likely causes

Equipment problems

• Inverter failures (one of the most common causes of zero or low production)
• Failed microinverters or optimizers on individual panels
• Damaged panels, loose wiring, or tripped breakers

Design problems

• Panels placed on roof faces that get poor sun
• Shading from trees, chimneys, neighboring buildings, or other roof features that wasn't accounted for
• A system that's simply too small for the savings promised

Estimate problems

• Production estimates based on overly optimistic assumptions
• Estimates that ignored shading or roof orientation

Activation problems

• A system that was never granted permission to operate by the utility, or was switched off for an inspection and never turned back on

Step 5: Contact the company, in writing

If your system is under a lease or PPA, the company is usually responsible for maintenance and repairs. If you own it, the installer's workmanship warranty and the manufacturers' equipment warranties may apply.

Contact the company in writing (email or the method your agreement specifies) and keep copies. Describe:

• What the estimate or guarantee says
• What the system actually produced, with dates
• Any error messages or outages
• A request for inspection and repair

Write down every phone call: date, time, who you spoke with, and what they said. If the company fixes the problem, great. If you get the runaround, those records become important.

Step 6: Check your production guarantee

Some leases and PPAs include a production guarantee: a promise that the system will produce a certain amount, with a credit or refund if it falls short. Read the details carefully:

• How is production measured? Usually by the company's monitoring.
• Over what period? Annual, or cumulative over several years.
• What's the remedy? Often a payment per kWh of shortfall.
• Do you have to claim it? Some require you to request the payment.
• Are there exclusions? For example, shading from new trees, or outages you didn't report.

Step 7: If the problem isn't fixed

When repeated requests go nowhere, or the problem turns out to be a design flaw or an inflated estimate rather than a repairable defect, a more formal approach may make sense. Depending on the facts, possible resolutions can include repairs or equipment replacement, credits or refunds for lost production, payment adjustments, or in some cases cancellation. Results vary.

Underperformance combined with an inflated sales estimate is also a common sign of misrepresentation. See signs your solar contract was misrepresented and whether you can cancel a solar contract after installation. If your agreement requires arbitration for unresolved disputes, our guide to how arbitration works for solar disputes explains the process.

Common mistakes to avoid

• Waiting too long. Production guarantees often have claim periods, and monitoring data may not be kept forever. Start documenting as soon as you notice a problem.
• Relying only on phone calls. Calls are easy to forget and hard to prove. Follow every call with a short email summarizing what was said.
• Climbing on the roof. Don't try to inspect or clean panels yourself on a pitched roof. It's dangerous and may affect your warranty.
• Letting a third party "fix" a leased system. With a lease or PPA, unauthorized repairs can violate your agreement. Go through the company first.

Your underperformance checklist

• ☐To gather: Production estimate or guarantee (from proposal and contract)
• ☐To gather: 12+ months of monitoring data (screenshots or exports)
• ☐To gather: 12+ months of utility bills
• ☐To gather: List of error messages and outages, with dates
• ☐To gather: Copies of every message to and from the company
• ☐To gather: Notes from every phone call
• ☐To gather: Photos of shading, damage, or equipment issues

Every agreement and every situation is different. Results vary, and no one can promise a specific outcome.

This article is general information, not legal advice. Laws and utility rules change, and your situation may differ. Solar Resolution Group is not a law firm.