A solar proposal usually arrives as a single glossy number: a monthly payment, a “net cost,” or a savings figure. All three can be built on assumptions you have not been shown. The practical move is to stop reading the quote as a price tag and start reading it as a stack of separate numbers, each one either stated by the seller or unknown.

The U.S. Department of Energy describes shopping for rooftop solar as breaking into three categories: what quality of equipment to buy, how to finance the system, and which contractor installs it (DOE success story, 2022). A quote is where those three meet. Read it in that order and the form becomes far less slippery.

Start with the cash price

Before any loan is discussed, there is a cash price: what the system and installation would cost if you paid outright. Everything else on the form is a variation on that number. The Consumer Financial Protection Bureau advises that if you decide to install solar, you should ask the salesperson what the cash price of the system is, and if they will not give you a straight answer, consider going to a bank or credit union for financing and bringing that loan offer to the installer (CFPB consumer advisory).

That is not just shopping advice. It is an accounting instruction. Write the cash price at the top of your own sheet. Any later number gets compared back to it, never to another monthly payment.

Separating equipment price from financing total

A solar-specific loan is typically a fixed-term, usually fixed-rate installment loan that covers the price of the panels and installation, as the CFPB's solar financing research describes it (CFPB Issue Spotlight). The loan principal, though, can be larger than the cash price.

The CFPB has found that some lenders include substantial markups and fees that can increase the loan principal by 30 percent or more above the cash price. These fees, often called dealer fees within the industry, are frequently built into the loan principal without being labeled as a markup over what you would pay for the installation. The agency describes hidden fees as typically 10 to 30 percent of the cash price and capable of exceeding 50 percent (Issue Spotlight).

So the first subtraction on your sheet is this: cash price versus loan principal. If they differ, the gap is the financing cost that is not interest, and it should be visible before you compare interest rates.

The 18-month payment step

Many solar loans are structured to raise the required monthly payment after 18 months unless the borrower makes a large prepayment of principal, typically around 30 percent, which corresponds to the presumed federal tax credit. The CFPB says many consumers are surprised by this expectation, do not receive the assumed credit, or do not have the funds to make the prepayment, and therefore face large increases in their monthly payments (Issue Spotlight). The CFPB consumer advisory frames it plainly: the monthly payment often jumps higher after 18 months unless you make a payment matching the projected tax credit, whether or not you ultimately receive it.

Not every loan works this way. But if a quote shows one monthly figure, look for the second one. Write down the payment before and after the step, and the prepayment amount that avoids it.

Claims about tax credits and savings

The federal residential solar credit is non-refundable. It reduces federal income tax liability by a percentage of the installation cost, and if the credit exceeds what you owe, it can only reduce your liability to zero. Households with no federal tax liability cannot claim any of it (Issue Spotlight). The CFPB also notes that because the seller does not know your tax situation, a projected credit may not be accurate, and the actual credit may take time to arrive.

This matters for how the quote is presented. Some salespeople deduct a projected credit from the loan amount and show the lower “net cost,” which makes the price seem smaller than the total amount being borrowed. Read the loan principal as the number you actually owe; treat any credit as a separate, uncertain item you would verify with your own tax circumstances.

Savings claims deserve the same treatment. Solar installations can lower energy bills, but the CFPB says the exact savings are hard to predict and can vary significantly by location and season, and it identified misleading statements that panels will eliminate future energy bills. A projected annual savings figure on a quote is an estimate, not a term of the contract.

A worked example, clearly hypothetical

The figures below are invented round numbers used to show the arithmetic. They are not a price benchmark.

Suppose a quote shows a cash price of $20,000 and a loan with a $24,000 principal, a $0 downpayment, 5 percent APR over 20 years, and a payment that rises after 18 months unless $7,200 is prepaid. On your sheet:

  • Cash price: $20,000, the reference figure.
  • Loan principal: $24,000, which is $4,000 above cash price — financing costs that are not interest.
  • Prepayment to avoid the step: $7,200, which is 30 percent of the $24,000 principal.
  • Monthly payment before and after month 18: copy both from the quote.

What you would not do is subtract $7,200 from $24,000 and call that the price. You would also not compare the post-step monthly payment with another installer's cash price. Both moves hide the gap the CFPB warns about.

Questions to ask the salesperson

  • What is the cash price of the system and installation?
  • What is the loan principal, and what fees are included in it beyond the cash price?
  • Is there a prepayment required to keep the monthly payment level, and after how many months does it apply?
  • What is the monthly payment before and after that point?
  • Does any figure on this page assume a tax credit I may not receive?
  • What savings estimate is shown, and over what period and assumptions?
  • Which panel and inverter models are specified, and what warranty documents come with them?

The DOE homebuilder guidance notes that modules are expected to last 25 years or more while producing more than 80 percent of original power, which is a general expectation, not a manufacturer warranty (see our equipment and warranty questions).

Where the quote stops and the site starts

A quote form cannot tell you whether your roof is suitable, what utility rules apply at your address, or what your tax position is. The DOE homebuilder guide notes that interconnection agreements with the local utility are required before activation and vary greatly by utility and local authority. Those are site-specific questions for a qualified assessor and your utility, not something a comparison page can estimate.

If you want to put two or three quotes on the same footing, enter them at our comparison desk, and read what the numbers can and cannot tell you in what a solar comparison can and cannot estimate. The most useful next step is usually the least glamorous: copy the cash price, the loan principal, the prepayment amount, and both monthly payments onto one sheet before you talk to anyone again.