How to Vet a Solar Installer: 9 Questions Most Homeowners Forget to Ask

You have done the math. Solar makes sense for your home. Now comes the part that trips up more homeowners than any other step in the process: choosing who actually puts the panels on your roof.

The solar installation industry has grown fast — the Solar Energy Industries Association (SEIA) estimates there are now over 10,000 solar companies operating in the United States^[1]. Most are legitimate. Some are excellent. A few will disappear before your warranty does. The difference between a great installation and a problematic one often comes down to the questions you ask before signing anything.

Here are nine questions that experienced solar buyers ask — and that most first-timers never think of.

1. Are You NABCEP-Certified, and Who on Your Crew Holds the Certification?

The North American Board of Certified Energy Practitioners (NABCEP) certification is the gold standard for solar installers. But there is a subtlety most people miss: a company can market itself as "NABCEP-certified" when only one person in the organization holds the credential — and that person might never visit your roof.

Ask specifically: will a NABCEP-certified installer be on-site during your installation, or at least conducting the design review? Companies with multiple certified professionals on staff tend to deliver higher-quality work. According to NABCEP, certified professionals have completed at least 58 hours of advanced training and passed a rigorous examination^[2].

2. What Happens If You Go Out of Business During My Warranty Period?

This question makes some salespeople uncomfortable, which is exactly why you should ask it. Solar panel manufacturers typically offer 25-year product warranties and 25-30-year performance guarantees. Your installer likely offers a separate workmanship warranty covering the actual installation — typically 10 to 25 years.

But what good is a workmanship warranty if the company folds in year three? Ask whether the installer carries warranty insurance through a third party like SolarInsure or Mosaic. Some larger regional installers have third-party warranty backstops that survive the company itself. Others do not. The answer tells you a lot about how the company plans for the long term^[3].

3. Can I See Permits and Inspection Pass Rates for Recent Jobs in My Municipality?

Every solar installation requires permits and inspections from your local authority having jurisdiction (AHJ). Good installers pass inspections on the first try routinely. Problematic installers get red-tagged repeatedly, which delays your interconnection and costs you money in lost production every day you wait.

Ask for their first-pass inspection rate. Top installers achieve 95% or higher. If a company cannot tell you this number, that itself is informative. You can also call your local building department and ask whether the company has a history of permit issues.

4. Who Manufactures the Panels and Inverters You Are Proposing, and Why?

Some installers push whatever equipment gives them the highest margin, not what is best for your roof, shade conditions, or budget. A trustworthy installer should be able to explain why they recommend specific equipment for your situation.

In 2026, the Tier 1 panel manufacturers include LONGi, Trina, Canadian Solar, REC, QCells, and SunPower (Maxeon). For inverters, the major players are Enphase (microinverters), SolarEdge (optimizers), and increasingly hybrid inverter options from companies like Sol-Ark and SMA for battery-ready systems. Ask why they chose what they chose — a good answer sounds like engineering, a bad answer sounds like a sales pitch^[4].

5. How Do You Handle Roof Penetrations, and What Is Your Leak Rate?

Every traditional roof-mounted solar installation involves drilling into your roof. The most common mounting systems — such as IronRidge and Unirac — use lag bolts with flashing to create a waterproof seal. But the quality of the installation matters enormously.

Ask the installer about their attachment method, flashing approach, and what sealant they use. Then ask the hard question: what is their callback rate for roof leaks? Industry-wide, the rate is roughly 1-2% for properly installed systems, but that figure is much higher for companies cutting corners. If they claim zero leaks ever, they are either very small or not being honest^[5].

6. What Is Your Installation Timeline from Signed Contract to Permission to Operate?

This is where expectations diverge most from reality. Many homeowners expect solar panels producing power within a few weeks of signing. The actual timeline from contract to Permission to Operate (PTO) — the date your utility allows you to export power — averages 60 to 90 days nationally, though it varies significantly by state and utility.

The breakdown typically looks like this: design and engineering (1-2 weeks), permitting (2-6 weeks depending on your AHJ), installation day (1-2 days for most residential systems), inspection (1-2 weeks), and utility interconnection (2-6 weeks). Ask the installer to give you a realistic timeline specific to your area and utility. If they promise four weeks, they are either in a very fast jurisdiction or overpromising^[6].

7. Will You Provide a Production Guarantee, and What Are the Terms?

A production guarantee means the installer commits to your system producing a specific number of kilowatt-hours per year. If it falls short, they compensate you — typically through a credit or payment for the difference.

Not every installer offers production guarantees, but the ones that do tend to be more confident in their design work. When evaluating a guarantee, pay attention to the measurement period (annual is standard), the threshold below which compensation kicks in (often 90-95% of projected output), and what happens in years with unusual weather. A production guarantee backed by monitoring data is one of the strongest indicators of installer confidence^[7].

8. How Do You Handle Change Orders and Unexpected Costs?

The most common source of frustration in solar installations is unexpected costs that surface after the contract is signed. A tree that needs trimming, an electrical panel that needs upgrading, a roof section that needs repair before panels go on — these are all legitimate costs, but they should be identified during the site survey, not after you have already committed.

Ask the installer: what does your site survey include, and under what circumstances would the final price differ from the quote? Companies that do thorough site surveys — ideally including attic inspection and electrical panel assessment — generate fewer surprises. Companies that quote from satellite imagery alone tend to produce more change orders. A 2025 EnergySage survey found that 18% of solar buyers experienced unexpected costs after signing, with electrical panel upgrades being the most common^[8].

9. Can I Speak with Three Customers Who Had Their Systems Installed More Than Two Years Ago?

Recent references are easy to find. Anyone can deliver a good first impression. The real test is how a company performs two, five, or ten years into the relationship. Long-term customers can tell you about monitoring responsiveness, warranty claim handling, and whether the company follows through on promises.

Ask specifically for customers whose systems are at least two years old. If the company hesitates, it could mean they have not been around that long, or that their older customers are not happy. Either answer is useful information.

Red Flags That Should Make You Walk Away

Beyond the questions above, watch for these warning signs during your evaluation:

High-pressure sales tactics. Any company that tells you the price is only good today or this week is using a technique borrowed from used car lots, not professional contracting. Legitimate solar pricing does not expire overnight.

No site visit before quoting. Satellite imagery and AI tools are useful for preliminary estimates, but a final quote without a physical site visit is a red flag for change orders and surprises.

Subcontracting everything. Some solar companies are essentially marketing firms that subcontract all installation work. Ask whether the crew that installs your system is employed by the company or subcontracted. Subcontracting is not automatically bad, but you want to know who is actually responsible for workmanship quality.

Cannot explain your utility rate structure. Your installer should understand your utility rates, net metering rules, and time-of-use schedules. If they cannot explain how your specific rate structure affects your savings estimate, their financial projections are unreliable.

How to Compare Quotes Effectively

Once you have gathered quotes from at least three installers — and the industry consensus recommends three to five — compare them on a cost-per-watt basis rather than total system cost alone. In early 2026, the average residential solar installation cost is approximately $2.75 to $3.50 per watt before incentives, depending on your state and system size. After the 30% federal Investment Tax Credit, that drops to roughly $1.93 to $2.45 per watt^[9].

But cost per watt is just the starting point. Compare the estimated annual production, the equipment specifications, the warranty terms, the financing options, and the timeline. A quote that is 10% cheaper but uses lower-tier equipment and offers a shorter workmanship warranty may cost you more over the 25-year life of the system.

The EnergyScout solar assessment tool can help you establish a baseline for what solar should cost in your area and what production to expect based on your roof, giving you a solid foundation for evaluating quotes. You can also use the incentive search to make sure your installer has accounted for every available rebate and credit at your zip code.

The Bottom Line

Choosing a solar installer is a 25-year decision disguised as a one-day transaction. The panels on your roof will likely outlast your next car, your current phone, and possibly your roof itself. Spending an extra week asking tough questions upfront can save you thousands of dollars and years of frustration.

The best installers welcome hard questions. They see them as a sign that you are a serious buyer who will appreciate quality work. If asking these questions makes a company uncomfortable, they have done you a favor by showing you who they are before you signed the contract.

Ready to start evaluating solar for your home? Get your free solar assessment on EnergyScout.org and see what solar could save you based on your actual roof and energy usage.

Sources

1. SEIA — Solar Industry Research Data
2. NABCEP — Certification Programs
3. EnergySage — Understanding Solar Panel Warranties
4. NREL — Solar Market Research and Analysis
5. IronRidge — Mounting System Resources
6. SEIA — Solar Permitting Best Practices
7. EnergySage — Solar Production Guarantees Explained
8. EnergySage — Solar Marketplace Data
9. NREL — Residential Solar Cost Benchmark