How to Evaluate Solar Panel Companies: 9 Questions to Ask Before You Sign

Choosing a solar installer is one of the biggest decisions a homeowner makes. A good installer saves you money for 25 years. A bad one leaves you with a poorly designed system, voided warranties, and no one to call when something goes wrong.

Here are the 9 questions that separate the reliable installers from the ones to avoid — regardless of where you live.

1. Are They Licensed and Certified?

In the US, solar installers should hold a valid contractor's licence in your state — look for a C-10 (electrical) licence or equivalent. Employees should ideally be NABCEP (North American Board of Certified Energy Practitioners) certified — the gold standard in solar installation credentials.

In the UK, installers should be MCS (Microgeneration Certification Scheme) certified, which is also required to claim the Smart Export Guarantee (SEG) payments. RECC (Renewable Energy Consumer Code) membership is a further quality signal.

Always verify licences independently — don't just accept a claim. In the US, check your state contractor licence board. For NABCEP, verify at nabcep.org.

2. How Long Have They Been Installing Solar?

Look for at least 3–5 years of solar-specific installation experience in your region. Solar system design is climate-dependent — an installer experienced in sunny Arizona may not design optimally for a cloudy northwest climate, and vice versa.

Ask: how many systems have they installed? Can they provide references from customers with systems installed 3+ years ago? A customer whose system has been running for 3 years and performs as promised is much better evidence than any brochure.

3. What Equipment Do They Propose?

The three main components to evaluate:

Solar panels: Tier 1 manufacturers (those with bankable, publicly traded parent companies) include LG, Panasonic, REC, SunPower, Q Cells, and Jinko Solar. Look for panels with at least a 25-year product warranty and a production guarantee (typically 80%+ output at year 25).

Inverters: Enphase (microinverter), SolarEdge (string inverter with optimisers), and Fronius are the most widely trusted brands in residential solar. Ask why they recommend the inverter type they're proposing — microinverters add cost but eliminate single-point failure and work better in partial shade.

Racking and mounting: Often overlooked. IronRidge, Unirac, and SnapNrack are reputable US brands. The racking must be warrantied independently of the installer — if the installer goes out of business, the rack manufacturer's warranty should still stand.

4. What Warranties are Included?

A complete solar installation should include three separate warranties:

• Panel product warranty: Covers manufacturing defects — typically 12–25 years. Longer is better.
• Panel performance/production warranty: Guarantees output degradation rate — typically 80–90% at year 25. This is the warranty that matters most for your long-term energy savings.
• Workmanship warranty: Covers the installer's work — roof penetrations, wiring, mounting. This varies enormously: 1 year is poor, 10 years is good, 25 years is excellent. This is a major differentiator between installers.

Always read the workmanship warranty terms carefully. Some installers offer a 10-year warranty but exclude roof penetrations or limit coverage in ways that make it nearly worthless. Ask specifically: "If my roof leaks due to the solar installation within the warranty period, what is covered and what is the process?"

5. How to Get and Compare Quotes

Get at least 3 quotes from different installers for the same system specification. To compare them fairly, ensure each quote specifies:

• System size in kW (DC and AC)
• Panel make, model, and wattage
• Inverter make and model
• Racking system
• Estimated annual production in kWh
• Cost before and after incentives
• Warranty terms for panels, inverter, and workmanship separately

The lowest quote is rarely the best value. Compare cost per watt ($2.50–$4.00 is typical in the US in 2026; £1,800–£2,400 per kWp in the UK) and the quality of the components and warranties.

6. Red Flags to Watch For

• High-pressure sales tactics: "This offer expires tonight" is a manipulation technique. A reputable installer will give you time to consider and compare.
• No local physical presence: Installers who are difficult to contact after signing are a common source of complaints. Prefer companies with a local office you can visit.
• Unrealistic production estimates: If an installer's estimated annual production is significantly higher than the others, ask them to justify it with production modelling software output (PVWatts, SAM, or Helioscope). Be sceptical of estimates that seem optimistic.
• Vague warranty terms: Any installer unwilling to put clear warranty terms in writing before you sign is a red flag.
• Roof penetrations not included in workmanship warranty: This is where water damage claims most commonly originate.

7. Financing Options: What to Know

Cash purchase: Highest lifetime return. You own the system outright, claim all incentives (Federal ITC in the US, SEG in the UK), and all savings are yours.

Solar loan: Buy the system with financing. You still own it and claim incentives. Ensure the loan term is shorter than the system's payback period — typically 7–12 years for solar.

Solar lease or PPA: The installer owns the system and sells you the electricity at a fixed rate. You claim no incentives and the savings are lower, but the upfront cost is zero. Read the escalator clause carefully — some PPAs increase the rate 2–3% per year, which may reduce your savings significantly over 20 years.

Home equity or HELOC: Often the lowest interest rate available for solar financing. Interest may be tax-deductible in the US.

8. What Happens After Installation?

A quality installer handles:

• Permit application and inspection scheduling with your local authority
• Utility interconnection application (required to feed excess to the grid)
• Incentive application assistance (ITC, state credits, SEG registration)
• System monitoring setup so you can verify performance

Ask specifically: "What is your process if my system underperforms the estimated production?" A confident installer with a production guarantee will have a clear answer.

Frequently Asked Questions

How do I find a good solar installer?

Start with NABCEP-certified installers (US) or MCS-certified installers (UK) — these have verified credentials. Get at least 3 quotes. Ask for references from customers with 3+ year old systems. Check reviews on independent platforms (Google, Trustpilot) not just the installer's own website. Avoid installers who pressure you into same-day decisions.

What should a solar quote include?

Panel make, model, and wattage; inverter make and model; racking system; system size in kW DC and AC; estimated annual production in kWh; total cost before and after incentives; and all three warranties (panel product, panel performance, and workmanship) with specific terms, not just the number of years.

What is a fair price for solar panels in 2026?

In the US, $2.50–$4.00 per watt installed (before ITC) is the typical range in 2026 for a standard residential system. Below $2.50/W warrants scrutiny of component quality and warranty terms. Above $4.50/W without premium components or unusually complex installation is overpriced. In the UK, £1,800–£2,400 per kWp installed is typical.

What warranty should a solar installer offer?

At minimum: 25-year panel performance warranty, 12-year panel product warranty, and 10-year workmanship warranty. A 25-year workmanship warranty from a financially stable company is the gold standard. Always read what the workmanship warranty actually covers — specifically whether roof penetrations and water damage are included.