If you collect 2–4 solar quotes, you’ll notice something fast: the totals can be wildly different even when the “system size” sounds similar. That’s because quotes vary by design, production assumptions, equipment choices, warranty terms, and what’s included (permits, monitoring, electrical work, roof details).
This guide gives you a simple, homeowner-friendly method to compare quotes line by line—so you can choose the best long-term value, not just the lowest number.
Start here: Solar Basics (Start Here)
Who this is for
- You already have multiple proposals and want a fair comparison.
- You want to spot hidden exclusions and “too good to be true” production estimates.
- You want a practical checklist you can use in 15 minutes per quote.
If you’re still mixing up kW vs kWh, read this first: kW vs kWh in Solar
What to gather before you compare (10 minutes)
- Your last 12 months of kWh usage (or as much as you have).
- Your rate plan type (flat rate vs time-of-use) and any minimum/fixed charges.
- From each quote: system size, estimated annual production (kWh/year), and equipment model numbers.
- Warranty terms (product + workmanship) and what is included (permits, interconnection, monitoring).
Use this bill guide to pull the right numbers: How to Read Your Electric Bill for Solar
Step 1) Normalize the price (so you’re not comparing apples to oranges)
Ask for the cash price—even if you plan to finance
Financed solar offers can bundle fees into the loan structure, which makes two “monthly payment” quotes hard to compare. Ask each installer for:
- Cash price (total installed price before incentives).
- Financed price (APR, term, and any upfront fees clearly stated).
Use cost-per-watt ($/W) to standardize
A quick normalization metric is:
$/W = Total installed cash price ÷ (System size in watts DC)
This doesn’t pick the winner by itself, but it helps you see if one quote is unusually high or low for your market. EnergySage and other marketplaces commonly recommend $/W as a standard comparison metric.
Important: confirm the quote’s system size is kW DC (panel rating) and not mixed with kW AC (inverter output). If it’s unclear, ask the installer to label it explicitly.
Step 2) Normalize production estimates (the #1 place quotes “cheat”)
Two quotes can be the same kW size but show very different kWh/year because they assume different:
- Shading impact (trees, chimneys, nearby buildings)
- Roof direction and tilt
- System losses (heat, wiring, inverter conversion, soiling)
- Weather dataset and modeling tool
To avoid “perfect world” estimates, always ask: What system-loss assumption did you use? A simple way to think about realism is using a loss factor / performance ratio approach.
Read this before trusting kWh/year: Solar Performance Ratio (PR) Explained
Quick sanity check question: “Can you show the assumptions used for shading and losses in the proposal?” If they can’t show it, treat the production estimate as marketing—not modeling.
Step 3) Compare value with one extra metric: $ per first-year kWh
Price-per-watt is helpful, but production matters too. Add this quick check:
$ per first-year kWh = Total installed cash price ÷ Estimated annual production (kWh)
This can reveal quotes that look “cheap per watt” but produce less energy due to roof layout, shading, or conservative design—and it can also reveal quotes that look great only because they assumed unrealistically high production.
Step 4) Compare equipment (because “Tier 1 panels” isn’t a spec)
Ask for exact model numbers and compare:
- Panels: model, wattage, warranty length, degradation terms if listed.
- Inverters: type and model (string vs microinverter vs optimizer-based systems).
- Monitoring: what app/platform, and whether you get system-level or module-level visibility.
Inverter type can affect shade behavior, serviceability, and cost. If one quote uses microinverters and another uses a string inverter, that is a design choice—not automatically better or worse.
Related: String Inverter vs Microinverter
Step 5) Compare scope, warranties, and service (where surprise costs happen)
Scope checklist (must be clear in writing)
- Permits and inspections included?
- Utility interconnection paperwork included?
- Monitoring hardware + setup included?
- Roof attachment / flashing approach described?
- Any electrical upgrades included (panel upgrade, disconnect, conduit runs, trenching)?
- Cleanup, patching, and project timeline listed?
Cost context: Solar Cost Breakdown
Warranty checklist (don’t accept vague wording)
- Product warranties: panels + inverter(s) (manufacturer).
- Workmanship warranty: installer’s coverage for roof penetrations, leaks, installation issues.
- Service process: Who comes out? Typical response time? Any trip fees?
Original value: Solar Quote Scorecard (copy/paste)
Fill this out for Quote A / B / C. The best choice usually becomes obvious.
| Category | Quote A | Quote B | Quote C | What “good” looks like |
|---|---|---|---|---|
| System size (kW DC, labeled) | DC size clearly labeled; layout shown | |||
| Est. annual production (kWh/year) | Assumptions disclosed (shading + losses) | |||
| Cash price | Clear total before incentives | |||
| Cost per watt ($/W) | Used to standardize price comparisons | |||
| $ per first-year kWh | Catches weak designs or inflated estimates | |||
| Panel model # | Exact model numbers listed | |||
| Inverter type + model | Matches roof/shade needs; monitoring included | |||
| Permits + interconnection | Included and handled by installer | |||
| Workmanship warranty | Clear term + what is covered | |||
| Electrical upgrades (if needed) | Written scope, not vague “if required” | |||
| Payment schedule | Milestones, not overly front-loaded |
Red flags (pause and ask questions)
- Pressure tactics (“sign today” for a special price).
- No model numbers (generic “premium panels” language).
- Huge production estimate with no shading/loss assumptions shown.
- Scope vague on permits, interconnection, or electrical work.
- Warranty/service process unclear (who repairs what, and how fast).
Don’t ignore billing rules (net metering vs net billing can change savings)
Your savings depend on how exports are credited and whether credits roll over or expire. That’s why two identical systems can have different savings under different tariffs. The U.S. DOE emphasizes checking local rules and consumer protections when going solar.
Read next: Net Metering Explained
When to consult a professional
- If a quote includes work near the meter, main panel, or service equipment, use licensed professionals for safety and code compliance.
- If your roof is older/complex or you suspect structural issues, consult a qualified roofing/structural professional before installation.
- If you’re considering batteries or backup, ask for a designed “critical loads” plan and code-compliant installation details.
- If your tariff is complex (time-of-use, riders, demand charges), ask a qualified solar pro to model savings under your exact rate plan.
