How to File a Solar Production Shortfall Claim

By Olivier Beauchemin · Updated May 2026

If your solar system has produced less than the production guarantee in your contract promised, you may be owed money. But the guarantee doesn't pay out automatically. You have to file a claim — and the burden of proof is on you, the homeowner.

This guide walks through the process step by step. It is not legal advice; it's a practical checklist for assembling a credible, well-documented claim. The stronger your documentation, the shorter the conversation with your installer.

Step 1: Find and Read Your Production Guarantee

You cannot claim against a guarantee you can't produce. The guarantee may be on your main contract, in a separate "Performance Guarantee" addendum, or in a system design exhibit. If you can't find it, search your email for "annual production," "kWh guarantee," or "performance guarantee," or request a copy from your installer in writing.

Once you have it, identify five things:

• The guaranteed production figure — the minimum kWh for the year, often expressed as a percentage of the design estimate
• The degradation schedule — how much the guaranteed figure drops each year
• The measurement period — annual, or cumulative over several years
• The reconciliation process — how shortfalls are calculated and what the installer owes
• The exclusions and deadlines — conditions that void the guarantee, and any window for filing

For a deeper breakdown of how these terms work, see our guide to solar production guarantees.

Step 2: Confirm the Shortfall Is Real

Before you file, make sure you actually have a shortfall — and that it isn't just weather. A claim that an installer can dismiss with "it was a cloudy year" is not a claim worth filing.

Pull your verified production data from your inverter monitoring system (Enphase Enlighten, SolarEdge, or similar) for the full measurement period. Then compare it not just to the guaranteed figure, but to a weather-adjusted expected baseline — what a healthy system of your size and orientation should have produced given the actual weather. If the shortfall holds up after weather is accounted for, you have a real claim.

Step 3: Calculate the Dollar Amount

Your contract specifies the formula. The common structure is: the installer owes you the value of the missing energy, calculated as the shortfall in kWh multiplied by your utility rate.

Here is the general shape of the calculation — always use your contract's exact formula and figures:

1. Guaranteed production for the period, adjusted by the contractual degradation schedule for the year in question
2. Minus your actual production for the same period, from your monitoring data
3. Equals the shortfall in kWh
4. Multiplied by the compensation rate in your contract — this may be your current utility rate, a fixed rate stated in the contract, or another defined value

Write the calculation out explicitly, with every number sourced. An installer is far more likely to accept a claim that shows its work than one that simply asserts a dollar figure.

Step 4: Pre-Empt the Exclusions

Most guarantees exclude shortfalls caused by "changed conditions" — new shading from tree growth, roof modifications, system tampering, grid outages, or extreme weather events. Your installer will likely raise these. Get ahead of it:

• New shading: Document that the roof is in the same condition as at installation. If trees have grown, note that predictable tree growth should have been accounted for in the original site assessment.
• Homeowner actions: Confirm you haven't modified the roof, added obstructions, or altered the system.
• Outages and curtailment: If the utility caused production loss, that's worth noting — but it's generally a genuine exclusion, so account for it honestly.

An honest claim that acknowledges legitimate exclusions is more credible than one that ignores them.

Step 5: Assemble the Claim Package

Submit a written claim — email or letter, so there's a record. Include:

• A copy of the production guarantee, with the relevant terms highlighted
• Your verified production data for the measurement period
• The weather-adjusted analysis showing the shortfall isn't explained by weather
• The dollar calculation, with every figure sourced
• A brief statement that no homeowner-caused changed conditions apply
• A clear request for the remedy specified in your contract, and a reasonable response deadline

Step 6: Mind the Deadline

Many contracts require the homeowner to initiate reconciliation within a specific window after the measurement period ends. Miss it, and you may forfeit that year's claim entirely. Check the deadline before you do anything else, and file with time to spare.

If the Installer Is Out of Business

A production guarantee is a contractual obligation of the installer. If the company is gone, the guarantee is usually worthless — it's an unsecured promise that disappears with the entity. Equipment warranties on the panels and inverters generally pass through to the manufacturers, but the production guarantee itself typically does not survive. See our guide on what to do when your solar installer goes out of business.

How OwlWatt Helps

OwlWatt is built for exactly this process. It tracks your production against your guarantee terms, generates the weather-adjusted baseline that defeats the "cloudy year" objection, and produces documentation — production data, weather analysis, and a dollar-denominated shortfall — in the form you need to support a claim. It also alerts you well before your reconciliation deadline, so you never lose a claim to a missed window.