Comparing solar quotes is mostly a bookkeeping exercise, and that is the honest reason to do it. The Solar Comparison Desk takes up to three quotes you type in — kW DC, cash price, down payment, APR, term, loan principal — and puts them on the same footing. It turns those numbers into things you can actually read: what you pay up front, what you borrow, what the loan costs across its life, and how the financed total compares with the cash price of the same system.
What it does not do matters just as much. It does not look at your roof, model your energy use, predict your bill, set a tax credit amount, or decide whether you qualify for a loan. Those questions depend on facts about your house, your taxes, your utility and your lender that no comparison table is given. Below is a plain account of where the arithmetic stops and where a real assessment has to begin.
What the comparison calculates
Three inputs do most of the work. The first is the cash price of the system: what the installer would charge if you paid without a loan. The second is the loan principal: the amount actually borrowed, which is not always the same as the cash price. The third is the financing terms — down payment, APR and term — which determine the cost of borrowing the principal.
Keeping the first two separate is the point. The Consumer Financial Protection Bureau has found that some lenders include markups and fees that can raise the loan principal by 30 percent or more above the cash price, and that these fees are often not shown as a markup from the total cash price (CFPB Issue Spotlight on solar financing). That finding covers some lenders, not all. But it explains why a financed total and a cash price should never be placed next to each other as if they were the same kind of number.
The comparison also surfaces a specific structural feature worth understanding before you sign anything: many solar loans are set up so the required monthly payment rises after 18 months unless you prepay a large share of the principal, typically 30 percent — the presumed tax credit amount. The CFPB describes this as a common structure that surprises some borrowers (CFPB consumer advisory). If your quote includes a payment step, the table will show the two payment amounts rather than a single blended figure.
What it does not estimate: roof, savings, tax credit, tariff
Each of these is a judgment about your specific situation, and the comparison has no way to make it.
Roof suitability
The Department of Energy's guidance for homebuilders notes that panels typically perform best on unshaded, south-facing roofs with a slope between 15 and 40 degrees, and that any orientation between southeast and southwest can work well (DOE Solar Energy Guide for Homebuilders). That is general guidance, not a verdict on your roof. Shade from trees, chimneys or adjacent peaks, structural capacity for panels and racking, and the condition of the roof surface all require someone to look. A comparison page cannot see any of it.
Energy savings
Installations can lower bills, but the CFPB states that projected savings are hard to predict and vary by location and season, and it flagged marketing that claims panels will eliminate future energy bills entirely. The comparison will show a savings figure only if you type one in, and it will label it as your assumption, not a projection.
Tax credit
The federal residential credit is non-refundable: it reduces federal income tax liability and cannot exceed it. A seller does not know your tax situation, which is why the CFPB warns against quotes that subtract an assumed credit from the loan amount to present a lower "net cost." The credit's value has varied over time and never exceeded 30 percent. The comparison does not apply a percentage for you. If a quote mentions one, enter it as a stated term and check it against current IRS guidance yourself.
Utility rates and tariffs
Nothing about net metering, time-of-use pricing or export compensation is assumed. The DOE guide notes that an interconnection agreement with the local utility is needed before activation and that these agreements vary greatly by utility and local authority. Your utility's current rules govern; the comparison does not carry them.
Where a suitability question has to go
Whether solar works on your particular house is a site-specific question. Shade, roof structure, electrical panel capacity and local code all sit with people who can inspect the property. The DOE guide notes that power is wired into the home's main electric panel, with requirements for labeling, panel sizing and breaker placement, and that utilities may want to inspect the system. An installer handles the interconnection paperwork, but the answer to "will this work here" comes from an assessment, not a spreadsheet.
A hypothetical worked example
To show the mechanics, here is a made-up case with round numbers. None of these figures come from a real quote, a real lender or a current market. Suppose a quote states a cash price of $20,000 and a loan principal of $26,000 — the difference being fees folded into the loan. With a $0 down payment, a 6 percent APR over 20 years, the monthly payment is roughly $186. Over 240 months that is about $44,700 in payments, of which roughly $18,700 is interest. If the loan also requires a 30 percent prepayment at month 18 to avoid a payment step, that is $7,800 due in a lump sum.
Compare that with a second hypothetical quote: same $20,000 cash price, principal of $20,000, 7 percent APR over 15 years. The payment is about $180, and the total paid is roughly $32,400. The second loan has a higher headline APR but a smaller principal, and over its life it costs far less. That is exactly the confusion the cash-price anchor is meant to clear up. Both examples are hypothetical; they are not predictions of what any lender offers.
One related product deserves separate treatment. PACE loans are repaid through property tax bills, not ordinary loan payments. CFPB research found PACE borrowers' property taxes rose by about $2,700 per year, an 88 percent increase, and that most PACE borrowers were eligible for cheaper financing (CFPB PACE rule announcement). That page also states a rule effective March 1, 2026, requiring standard mortgage disclosures for PACE loans — check the current status before relying on it. PACE is a different product with different risks, and the comparison treats it as such.
How to correct an entry
If a figure turns out to be wrong — say you entered the financed total where the cash price belonged, or the payment before a step instead of after — correct it and re-run. The comparison exits only through numbers you provide, so a bad input produces a bad table. Where a quote is ambiguous, the CFPB advises asking the salesperson for the cash price and, if you don't get a straight answer, seeking financing from a bank or credit union and comparing proposals from multiple installers and lenders with a written breakdown of work, materials and cost.
Next step: before entering anything, find the cash price on each quote and write it down separately from the loan principal. Then run the comparison, and read the result as arithmetic on your inputs — not as an estimate of your savings, your roof or your taxes. For the line-by-line questions to ask, see Read a solar quote line by line.
