Why Solar Quotes Are Hard to Compare
Getting multiple solar quotes sounds like a straightforward way to find the best price. In practice, it's harder than comparing, say, car insurance quotes — because solar proposals rarely use a consistent format, often omit important details, and vary significantly in what's included.
One company might quote a 10 kW system; another might quote 8 kW. One might include monitoring equipment; another might not. One might use a production estimate based on conservative assumptions; another might inflate it to improve the apparent payback period. Comparing the bottom-line price without understanding these differences tells you almost nothing useful.
This guide walks through what a complete solar proposal should contain, which red flags indicate an incomplete or misleading quote, and which questions to ask before you sign.
What a Complete Solar Proposal Should Include
System Specifications
- Panel brand, model, and wattage — You should be able to look up the exact panel on the manufacturer's website to verify efficiency, performance warranty terms, and company reputation.
- Inverter brand and type — String inverter, microinverters, or power optimizers. Each has performance and cost tradeoffs worth understanding.
- System size in DC kilowatts (kW) — The nameplate capacity of the system.
- Expected annual production in kWh — How much electricity the system is expected to generate in a year, under that specific tool's assumptions about your location, shading, and roof orientation.
Pricing Breakdown
- All-in price including equipment, labor, permits, and interconnection fees
- Itemized cost or at minimum a price-per-watt figure so you can compare across quotes of different system sizes
- Any incentives assumed in the net price (so you can verify your eligibility independently)
Warranty Coverage
- Panel product warranty — Typically 10–12 years, covering manufacturing defects
- Panel performance warranty — Typically 25 years, guaranteeing minimum output at year 25 (80–87% of original rated output depending on brand)
- Inverter warranty — Typically 10–25 years depending on inverter type
- Workmanship warranty — How long the installer guarantees their labor and installation quality. This is one of the most important warranties and one that varies the most between installers.
Timeline and Process
- Expected timeline from contract signing to installation
- Expected timeline from installation to permission to operate (PTO) from the utility
- Who handles permitting, utility interconnection, and any required inspections
Red Flags in Solar Proposals
System sized only on your current usage without any efficiency discussion
If an installer sizes your system based on your current bills without asking about your home's efficiency profile, they're not doing the full job. A thorough company will ask about your windows, HVAC, and insulation — or at minimum ask whether you're planning any efficiency improvements — before finalizing system size. See why efficiency should come before solar.
Production estimates that seem too optimistic
Ask how the installer calculated the production estimate. Standard tools like PVWatts use your address, roof orientation, pitch, and system specs to generate realistic estimates. If the production estimate isn't based on your specific roof, it may be generic and unreliable. Inflated production estimates make payback periods look shorter than they'll actually be.
Vague or missing workmanship warranty
The workmanship warranty covers roof penetrations, wiring, racking, and installation quality. Leaks and installation failures can happen years after installation. A reputable installer offers a clearly stated workmanship warranty — typically 10–25 years — and backs it with a business that will still be operating when you need it.
High-pressure "today only" discounts
Solar pricing doesn't change daily. An installer who uses urgency tactics to pressure a same-day signature is more interested in closing a sale than in whether the system is right for you.
No mention of permits or utility interconnection
Every Illinois solar installation requires a local building permit and utility interconnection. If a quote doesn't address this, ask explicitly: who handles the permit applications, and are the permit fees included in the quoted price?
The Key Metric: Price Per Watt
To compare two quotes of different sizes on a level playing field, calculate the price per watt:
Price per watt = Total installed price ÷ System size in watts
A 10 kW system at $30,000 is $3.00/W. A 12 kW system at $38,400 is $3.20/W. Price per watt doesn't tell you everything — equipment quality and warranties matter too — but it puts quotes on the same scale so you can make meaningful comparisons.
Questions to Ask Every Installer
- How did you size this system — what methodology did you use?
- Did you account for any planned efficiency improvements to the home?
- What production simulation tool did you use, and can I see the inputs?
- What are the exact panel and inverter models in this proposal?
- What does your workmanship warranty cover, and for how long?
- Who performs the installation — your own crew or subcontractors?
- Who handles the permit applications and utility interconnection?
- What happens if the company goes out of business? Who services my system?
Frequently Asked Questions
How many quotes should I get?
Two or three from reputable local installers is sufficient for most homeowners. More than three makes comparison difficult and time-consuming. Focus on installers with a track record in your area and real references you can contact — not just online reviews.
Is the lowest price the best choice?
Not necessarily. Low-price solar is often achieved through lower-tier equipment, shorter warranties, or subcontracted installation with less quality control. The cheapest system that fails in year 8 or produces 15% less than projected isn't a deal. Evaluate the total value: price, equipment quality, warranty terms, and company reputation.
Should I get quotes from national installers or local companies?
National installers can offer competitive pricing due to volume. Local installers typically have stronger accountability — they're more likely to still be operating in 10 years to honor their workmanship warranty, and they often have more direct relationships with the local permitting offices and utility. SPM is locally based and handles all permitting and utility work directly.