You have obtained quotes from three solar installers. One is $2,000 cheaper than the others. Do you take it? Not necessarily. Solar is a 25-year investment — the cheapest upfront option can be the most expensive over the system's lifetime if it uses inferior components or comes from an installer who will not be around for warranty service.
This guide provides a 7-point checklist for comparing solar quotes side by side, with specific red flags and green flags for each category.
The 7-Point Solar Quote Comparison Checklist
1. Cost Per Watt (CPW)
CPW is the most objective price metric because it normalizes across different system sizes. Calculate it for every quote:
Compare CPW against your market's benchmark. For US, good is $2.50/W or below. For Europe, €1.40/W is the target. For Australia, A$1.20/W is competitive. See our full CPW guide for detailed benchmarks by market.
2. Panel Brand and Efficiency
Not all solar panels are created equal. The panel is the core of your system and will be on your roof for 25+ years.
| Panel Tier | Examples | Efficiency | Degradation | Warranty |
|---|---|---|---|---|
| Tier 1 | Longi, JA Solar, Trina, Jinko, Canadian Solar | 21-23% | 0.25-0.40%/yr | 25 yr product + performance |
| Tier 2 | Risen, Seraphim, GCL, DAH Solar | 19-21% | 0.40-0.55%/yr | 15-25 yr product |
| Tier 3 / Non-Branded | Generic white-label, unbranded | 17-19% | 0.50-0.70%/yr | 10-15 yr product |
A tier-1 panel with 0.30%/yr degradation will still produce 92.5% of nameplate power at year 25. A tier-3 panel at 0.65%/yr degradation drops to 83.8% — meaning 9% less energy over the system lifetime.
3. Inverter Brand and Type
Your inverter is the most likely component to fail within the system's lifetime. Inverter choice affects CPW, reliability, monitoring capability, and shade tolerance.
| Inverter Type | Brand Examples | Cost Impact | Warranty | Best For |
|---|---|---|---|---|
| String Inverter | SMA, Fronius, Sungrow, Huawei | Baseline | 5-10 yr | Simple unshaded roofs |
| Microinverters | Enphase, Hoymiles, APsystems | +$0.12-0.20/W | 10-25 yr | Complex roofs, shading |
| Power Optimizers | SolarEdge (with inverter) | +$0.05-0.12/W | 10-25 yr | Partial shading, module-level monitoring |
4. Warranty Terms
Warranties are where good installers differentiate themselves from budget operators. Three separate warranties matter:
- Panel warranty: 25-year product and performance warranty from a tier-1 manufacturer. The performance warranty guarantees at least 80-85% of nameplate power at year 25.
- Inverter warranty: 5-10 years standard. Some manufacturers (Enphase, SolarEdge) offer 20-25 year extended warranties for an additional cost.
- Workmanship warranty: This is the installer's own warranty on their labor and roof penetrations. Industry standard is 5-10 years. Anything less than 5 years is a red flag.
5. Promised Annual Yield (kWh/kWp)
Every quote should include an estimated annual energy yield. This is a critical number — if it is inflated, your payback and ROI calculations will be wrong.
Realistic specific yield values by climate zone:
| Climate Zone | Realistic Specific Yield | Inflated if Above | Example Markets |
|---|---|---|---|
| Tropical | 1,500-1,750 kWh/kWp | 1,850 kWh/kWp | Thailand, Nigeria, Colombia |
| Subtropical / Arid | 1,400-1,650 kWh/kWp | 1,750 kWh/kWp | India, Pakistan, Texas, Saudi Arabia |
| Temperate | 1,000-1,250 kWh/kWp | 1,350 kWh/kWp | UK, Germany, Northern US, Japan |
| High Latitude | 800-1,050 kWh/kWp | 1,150 kWh/kWp | Canada, Scandinavia |
Our P50 vs P90 yield guide explains how to independently verify yield estimates using PVGIS, NREL PVWatts, or your local solar radiation database.
6. Mounting System Quality
The mounting system holds your panels to the roof through wind, snow, and rain for 25 years. It is invisible after installation but critical for long-term performance and roof integrity.
- Rails: Aluminum alloy with stainless steel hardware. Ask if the brand is known (Schletter, K2, EcoFasten, Clenergy, or Unirac). Cheap zinc-plated steel rails rust over time.
- Roof attachments: Flashing mounts (L-feet with integrated flashing) are superior to sealant-only attachments. Standing seam requires S-5! clamps or similar.
- Wind rating: The system should be designed for your local wind zone. In cyclone/hurricane zones (Australia, Florida, Caribbean), the quote should reference AS/NZS 1170.2 or equivalent building codes.
7. Company Reputation and Service
An installer that goes out of business in year 3 leaves you with nobody to honor the workmanship warranty. Research each company:
- Years in business (5+ is preferred)
- Online reviews on Google, SolarQuotes, or equivalent platforms
- Accreditations and certifications (NABCEP in US, MCS in UK, CEC in Australia, RISE in Pakistan)
- References from previous installations in your area
- Response time for customer service inquiries
Quote Comparison Example: Quote A vs Quote B
Here is a realistic comparison for a 6.5 kWp system in Australia:
| Metric | Quote A — Budget | Quote B — Premium | Which Wins? |
|---|---|---|---|
| Total Price | A$8,000 | A$10,500 | Quote A |
| CPW | A$1.23/W | A$1.62/W | Quote A |
| Panel Brand | Tier-2 (19.5% eff) | Tier-1 Longi (22.1% eff) | Quote B |
| Inverter | Generic string 5kW | Fronius Symo 6kW | Quote B |
| Panel Warranty | 15 yr product + 25 yr performance | 25 yr product + 30 yr performance | Quote B |
| Inverter Warranty | 5 yr | 10 yr | Quote B |
| Workmanship | 5 yr | 10 yr | Quote B |
| Promised Yield | 1,650 kWh/kWp (high for Sydney) | 1,420 kWh/kWp (realistic) | Quote B |
| Mounting Brand | Generic aluminum rails | Clenergy (certified) | Quote B |
| Company History | 3 years, 50 installs | 12 years, 1,500+ installs | Quote B |
When the Cheaper Quote Actually Makes Sense
A budget quote can be the right choice if you are on a tight budget, plan to sell the property within 5-7 years (and the solar system adds resale value regardless of brand), or if the system is replacing an existing one and you already have infrastructure in place. In those cases, the short owner-occupancy period means premium components may not deliver their full value before you sell.
Use Our Free Solar Quote Comparison Tool
Our interactive quote comparator lets you paste the details from 2-4 quotes side by side, automatically calculating CPW, payback, ROI, and flagging unrealistic yield assumptions.
Compare your solar quotes now
Open the Quote Comparator →Data sources: NREL PVWatts, PVGIS, Australian PV Institute, SolarQuotes installer database, manufacturer specifications. Yield estimates are indicative and should be verified with site-specific modeling.
Last updated: July 2026 | Browse all guides