A solar proposal is unusual among home improvement documents because it bundles four separate things into one presentation: a piece of equipment, an installation, a financing product, and a projection of future savings. Each is negotiable and each should be evaluated separately.
Most homeowners compare the last one, the savings number, which is the least reliable of the four because it rests on assumptions the installer chose. The parts that are actually comparable sit further down the page.
Start With System Size and Cost Per Watt
System size is stated in kilowatts of direct current capacity. Dividing the total system cost by the wattage gives cost per watt, which is the standard way to compare solar quotes across different system sizes.
Published figures vary widely by source and market. Competitive marketplace data has tended to run lower than broader installed price surveys, and quotes in the same city can differ substantially between a national sales organization and a local installer. What matters is that you calculate it for each quote yourself, since a larger system at a lower price per watt may be better value than a smaller one at a higher rate.
Make sure you are comparing the same thing. Confirm whether the figure is before or after any incentive, and whether it includes a battery, since bundling storage into the system price distorts the comparison.
Then Look at Production, Not Just Size
Two systems of the same size on the same house can produce different amounts depending on panel efficiency, inverter type, orientation, tilt, and shading.
The proposal should include an annual production estimate in kilowatt hours, and it should say what modeling was used. Ask whether shading was measured on site with an instrument or estimated from satellite imagery, because trees and neighboring structures are the most common reason real production falls short of the projection.
Then compare production against your actual consumption, which is on twelve months of utility bills. A system sized to cover a share of your usage is a reasonable design. A system sized well beyond it deserves an explanation, particularly under net metering rules where excess export is compensated at less than retail.
Equipment Specifics
- Panels. Manufacturer, model, wattage per panel, and quantity. Check the product warranty and the performance warranty, which are different, and note the guaranteed output percentage at the end of the term.
- Inverter type. A string inverter is one central unit. Microinverters sit under each panel. Power optimizers are a middle approach. Microinverters and optimizers handle partial shading better and allow per panel monitoring. String inverters are usually less expensive and have fewer rooftop components.
- Inverter warranty, which is typically shorter than the panel warranty and is the component most likely to need replacement during the system's life. Ask what a replacement costs and who pays for labor.
- Racking and attachment method, and how roof penetrations are flashed.
- Monitoring, and whether there is an ongoing fee for it.
The Roof Question
Solar arrays last decades and are expensive to remove and reinstall. If your roof is in the second half of its life, the sequencing matters, and we cover it in should you replace your roof before going solar.
Ask what the installer's policy is if the roof needs replacement in ten years, and what removal and reinstallation would cost. Get the answer in writing.
What Is Excluded
Unusually low quotes often exclude work that will still be necessary. Ask specifically about:
- Electrical panel upgrades, which are common on older services and are a meaningful cost
- Tree removal or trimming, where shading is a factor
- Roof repairs identified during the site assessment
- Utility interconnection fees and any required meter change
- Permit fees and any structural engineering letter your jurisdiction requires
- Battery, if you are comparing a quote with storage against one without
The Financing Layer
Purchase, loan, lease, and power purchase agreement are fundamentally different transactions with different ownership, different obligations, and different consequences when you sell the house. That comparison is covered in buying, leasing, or financing solar in 2026.
Two specific things to check on any financed proposal. First, whether the quoted price includes a dealer fee, which is a charge the installer pays the lender and passes through in the system price. Cash and financed prices for the same system frequently differ for this reason, and the difference can be substantial. Ask for the cash price alongside the financed one.
Second, the escalator on a lease or power purchase agreement, which is the annual percentage increase in your payment. A payment that starts below your utility bill and rises at a fixed rate may not stay below it.
The Savings Projection Is the Least Reliable Part
Every proposal contains a twenty five year savings figure. It rests on an assumed rate of utility price inflation, an assumed production degradation curve, and an assumption about how your utility will compensate exported energy for the next quarter century.
The last of these is the weakest. Net metering rules have been changing in a number of states, generally in ways that reduce the value of exported power, which we covered in net metering changes are reshaping home solar quotes. A projection built on today's rules may not describe the next twenty years.
Ask what utility escalation rate was assumed. If it is higher than your utility's actual history, the savings figure is inflated. Ask the installer to show the projection at a lower escalation rate, and note how much the number moves.
Federal incentives have also changed, and nobody should budget from remembered figures. See what solar payback looks like without the federal credit and confirm the current position with a tax professional.
Practical Comparison Checklist
Put three quotes side by side and record for each: system size, cost per watt, estimated annual production, panel and inverter models, warranty terms, what is excluded, the cash price, and the financed price. That table is more useful than any of the three presentations.
Then verify the installer the same way you would any contractor, using the steps in verifying a contractor's license, insurance, and references.
If you want quotes for home solar, tell us about your home and we will connect you with installers serving your area. It is free to use, with no obligation to hire.