In short: To compare solar quotes properly, line them up on the same basis: system size, exact equipment, expected annual production, total price, price per watt, cost per kWh over the system’s life, warranties, financing terms and what’s excluded. The cheapest quote is often not the best value, and the most persuasive salesperson is often not the most reliable one.
Solar quotes can look very different even when they describe similar systems. One might exclude an electrical upgrade, another might hide fees inside a loan, and a third might quote unrealistically high production to make the savings look better. This guide shows you how to compare quotes fairly, with a worked example, a comparison sheet and a list of red flags.
Before you compare: get quotes you can compare
- Get at least three quotes from different, verified installers. See How to Choose a Solar Installer.
- Give each installer the same information: your last 12 months of bills, your goals (savings, backup, EV) and any roof constraints.
- Ask for an itemized written quote, not just a headline price or a monthly payment.
- Ask each installer to quote the same target, such as covering about 80–100% of your usage, so systems are comparable. See How Many Solar Panels Do I Need?
The 10 things to compare
1. System size (kW) and panel count
Bigger systems cost more but produce more. A quote for 6 kW and one for 8 kW aren’t directly comparable until you convert to price per watt and cost per kWh.
2. Exact equipment models
“High-quality panels” is not a specification. You want the panel brand and model, wattage, and the inverter or microinverter model. Check the specs against the datasheets: see Best Solar Panels for Homes and String vs Microinverters.
3. Expected annual production (kWh)
This is the most important number and the easiest to inflate. Ask how it was calculated: which software, what shading assumption, what losses. Sanity-check it against a free tool such as NREL’s PVWatts (US) or a similar estimator for your country. Typical yields are roughly 850–1,000 kWh per kW per year in the UK and about 1,100–1,800 in the US, depending on region (see our panel-count guide). If one quote promises far more than others for a similar system, ask why.
4. Total price and price per watt
Price per watt = total price ÷ system size in watts. It’s a useful first filter, but not the whole story, because equipment quality and inclusions differ.
5. Cost per kWh over the system’s life
Cost per kWh ≈ total price ÷ (annual kWh × years). Using 25 years (and ignoring small annual degradation for simplicity) shows what each kWh from your system will effectively cost you, which you can compare to your electricity price. See how to calculate your solar payback period.
6. What’s included and what’s not
Ask the installer to list, in writing, whether the price includes:
- Permit and inspection fees, and utility interconnection fees.
- Electrical panel or meter upgrades, if needed.
- Roof repairs, reinforcement or scaffolding (in the UK, scaffolding can be a significant line item).
- Monitoring hardware and app access.
- Trenching or extra cabling (for ground mounts).
- Battery-related items such as a gateway or backup panel, if you’re adding storage.
- Sales tax or VAT: confirm whether the price is before or after it.
- Removal and reinstallation of panels if you need roof work later.
7. Warranties
Compare product warranties, performance warranties and, crucially, the installer’s workmanship warranty (and roof-penetration warranty). Ask who pays for labor if a panel or inverter fails, and what happens if the installer goes out of business.
8. Financing terms
Ask for the total amount you’ll pay over the life of the loan or lease, not just the monthly payment. See the next section.
9. Incentives and savings assumptions
Check exactly which incentives the quote assumes and whether they apply to you. Incentive rules change and often differ for purchases, loans and leases. In the US, the federal residential rules have changed recently, so confirm current eligibility. Also check which net metering or export rules the savings estimate assumes.
10. Timeline and process
Compare estimated time from signing to switch-on, who handles permits and grid applications, and what happens if approvals are delayed.
Worked example: three quotes compared
Illustrative example only. These are fictional quotes to show the method. Use your own numbers.
Assume you use about 10,500 kWh per year.
| Quote A | Quote B | Quote C | |
|---|---|---|---|
| System size | 7.2 kW | 8.0 kW | 6.4 kW |
| Total price | $19,800 | $20,800 | $15,700 |
| Price per watt | $2.75 | $2.60 | $2.45 |
| Estimated annual production | 10,000 kWh | 10,600 kWh | 8,600 kWh |
| Share of your usage covered | 95% | 101% | 82% |
| Cost per kWh over 25 years | about $0.079 | about $0.078 | about $0.073 |
| Workmanship warranty | 10 years | 25 years | 2 years |
What the numbers show:
- Quote C is the cheapest per watt and per kWh, but it covers only 82% of your usage and has only a 2-year workmanship warranty. Ask what equipment it uses and why the warranty is so short.
- Quote B costs a little more in total than A but is cheaper per watt and per kWh, and it has a much longer workmanship warranty. It also covers all of your usage, which may or may not be ideal depending on your export rules.
- Quote A is the most expensive per watt and offers a shorter warranty than B, so you’d want a clear reason to prefer it, such as better equipment or a stronger local reputation.
The lesson: price per watt is a filter, not a verdict. Compare production, warranties, and what’s included before you decide.
Financing: where quotes hide the real cost
Cash vs loan
A low advertised interest rate doesn’t tell you the total cost. Some solar loans include a dealer or origination fee that is built into the financed price, which can raise the price by a substantial percentage (in some products, by 10–30% or more compared with the cash price). Ask for the cash price and the financed price side by side, plus the total repayment over the loan term. See Solar Loans vs Cash vs Lease and Solar Loan Interest Rates.
Leases and power purchase agreements (PPAs)
Watch the escalator: a payment that increases every year. For example, a $150 monthly payment growing at 2.9% a year reaches about $258 a month by year 20. Ask what happens if you sell your home: see What Happens to a Solar Lease When You Sell Your Home? Also confirm who owns the system, who’s responsible for maintenance and who gets the incentives.
Compare total cost, not monthly payment
A lower monthly payment can hide a higher total cost. Always compare total payments over the full term, including any fees, escalators and buyout costs.
Red flags in a solar quote
- Production estimate far above the others or above what a free tool like PVWatts suggests, without a clear reason.
- Guaranteed savings or “$0 electricity bill” promises without a transparent calculation.
- Vague equipment descriptions (“premium panels”) instead of specific models.
- No itemization, just a single price or monthly payment.
- Price much lower than every other quote with no explanation: missing components, cheap equipment or corner-cutting are typical.
- Pressure to sign quickly, such as “this price expires today” or “incentives are ending tomorrow” without evidence. Verify incentive deadlines yourself.
- “Free solar” or “government program” claims that don’t clearly explain who pays and how.
- Financing hidden in the price, or unwillingness to show the cash price.
- A large deposit compared with the work completed.
- Short workmanship warranty or unclear who honors the warranty if the company closes.
- No site visit or roof assessment before a firm quote.
- Estimated savings that assume an export rate or incentive you don’t actually qualify for.
Your quote comparison sheet
Copy this list and fill it in for each installer:
| Item | A | B | C |
|---|---|---|---|
| Installer and credentials verified | |||
| System size (kW), panel count | |||
| Panel and inverter models | |||
| Annual production (kWh) and how it was calculated | |||
| Total price (cash) | |||
| Price per watt | |||
| Cost per kWh over 25 years | |||
| Inclusions and exclusions (permits, upgrades, scaffolding, tax) | |||
| Warranties: equipment, performance, workmanship | |||
| Financing: total repayment, fees, escalator | |||
| Incentives and export rules assumed | |||
| Timeline and who handles permits | |||
| References checked |
Questions to ask when a quote looks too good, or too expensive
- Can you break down the price line by line?
- What software and assumptions did you use for the production estimate?
- Which incentives are included in this price, and what happens if they change?
- What would change the price after signing (roof condition, panel upgrade, design changes)?
- If I pay cash, what’s the price compared with financing?
- Who handles warranty claims, and what happens if you close?
Common mistakes
- Comparing only monthly payments or headline prices.
- Ignoring production estimates and warranty terms.
- Choosing the cheapest quote without checking what’s missing.
- Accepting financing without seeing the cash price.
- Comparing quotes that cover different system sizes as if they were the same.
- Signing after one visit, without competing quotes.
Next steps
- Collect at least three itemized quotes and fill in the comparison sheet.
- Check each production estimate against a free tool.
- Ask about financing totals, escalators and exclusions.
- Check references and warranty backing, then choose: How to Choose a Solar Installer.
Where to next:
Frequently asked questions
How do I compare solar quotes?
Compare system size, exact equipment models, expected annual production, total price and price per watt, cost per kWh over the system’s life, warranties, financing terms, inclusions and exclusions, and the assumptions behind the savings estimate.
What is a good price per watt for solar?
It varies by country, region, system size and equipment, and it changes over time. Rather than aiming for a single number, compare your quotes with each other and with current local cost guides, and check that the price includes everything you need.
How many solar quotes should I get?
At least three from verified installers. This helps you spot prices that are unusually high or low and items that one quote includes and another leaves out.
Is the cheapest solar quote the best?
Not necessarily. A lower price may reflect smaller system size, lower-quality equipment, missing items or a short workmanship warranty. Compare cost per kWh, warranties and inclusions.
How do I know if a production estimate is realistic?
Ask how it was calculated and compare it with a free tool such as PVWatts for your address and roof direction. Be cautious if one installer’s estimate is much higher than the others for a similar system.
Should I take the loan the installer offers?
Not automatically. Ask for the cash price and the financed price, check for dealer or origination fees, and compare with other loan options such as a bank loan or home equity loan.