Read four numbers first: system size in kilowatts (kW), year-one production in kilowatt-hours (kWh), price per watt, and net cost after the 30% federal credit. A fair cash price often lands near $2.50 to $3.00 per watt before incentives, with the U.S. average around $2.58/W. If a proposal hides the cash price behind a monthly payment, ask for the price per watt and the production estimate in writing before you compare anything.
Key takeaways
- Convert every quote to price per watt so different-sized systems compare on the same scale.
- Year-one production (kWh) drives your savings, not the panel brand on the cover page.
- The 30% Residential Clean Energy Credit lowers your tax bill, it is not an instant rebate the installer pays.
- A monthly payment with no cash price, no kW, and no kWh is a sales tactic, not a proposal.
- Separate the equipment warranty from the workmanship warranty. They cover different failures.
- Start With Four Numbers, Not the Monthly Payment
- System Size: What kW Actually Tells You
- Year-One Production: The kWh That Pays You Back
- Price Per Watt: The Great Equalizer
- Equipment Tier and Warranties
- Net Cost After the 30% Credit
- Financing Terms and the Dealer Fee Trap
- The Proposal Checklist
- Red Flags in a Proposal
- Two Quotes, Same Roof: A Worked Example
Two installers walk the same roof. One sends a single page with a $0-down offer and a payment of $129 a month. The other sends three pages: a 9.2 kW system, an estimated 13,400 kWh in year one, a price of $2.71 per watt, and a line showing what the federal credit takes off. Same house. Two documents that share almost no vocabulary. This guide decodes both so you can tell which one is telling you the whole story.
Start With Four Numbers, Not the Monthly Payment
A monthly payment is the easiest number to manipulate and the hardest to compare. Stretch the loan term, add a hidden fee, change the assumed interest, and the payment moves without the system changing at all. So ignore it for a minute. Find these four numbers in each proposal first:
- System size in kilowatts (kW) of DC capacity.
- Year-one production in kilowatt-hours (kWh).
- Price per watt, which is gross system price divided by watts.
- Net cost after the 30% federal tax credit.
If a proposal does not give you all four, it is not finished. Ask for the rest in writing. The U.S. Department of Energy's homeowner guide makes the same point about doing your own apples-to-apples math before signing.
The Department of Energy advises homeowners to gather multiple bids and compare them on equipment, financing, and warranty terms rather than on headline price alone, since the cheapest sticker can carry the weakest coverage.
DOE, Homeowner's Guide to Going Solar
System Size: What kW Actually Tells You
System size is the rated DC capacity of all the panels added together. A 9.2 kW system might be 23 panels at 400 watts each. Size tells you the ceiling of what the array can do, but two systems of the same kW can produce different amounts of energy depending on roof direction, shade, and equipment. That is why size alone never settles a comparison.
Watch for a quiet mismatch. A salesperson may quote a small system to land a low payment, then your bill barely drops because the array does not cover your usage. Or they oversize it so the payment looks like savings on paper while you bank more credits than your utility will ever pay you fairly for. Pull your last 12 months of electricity use, in kWh, off your utility bills and check that the proposed production roughly matches what you actually consume. The national average residential rate sits around the figure the EIA tracks, but your local rate is what makes a given system size pay off.
Year-One Production: The kWh That Pays You Back
Panels do not save you money. Kilowatt-hours do. Year-one production is the estimate of how much energy the system makes in its first year, and it is the number that drives every savings claim in the proposal. A bigger panel brand on the cover means nothing if the production estimate is soft.
Good proposals tell you how they got the number. They name a modeling tool, state the assumed sun hours for your area, and apply a derate for real-world losses like heat, wiring, and inverter conversion. The DOE notes that panel output declines slightly each year and that real production depends on orientation, tilt, and temperature, not lab ratings. Ask whether the estimate accounts for that degradation and real-world derate. If two proposals show wildly different production for the same roof, one of them is using rosier assumptions to sell a bigger savings story.
Price Per Watt: The Great Equalizer
Price per watt is how you compare a 7 kW system to an 11 kW system without doing mental gymnastics. Take the gross system price, before any incentive, and divide by the system size in watts. A 9.2 kW system priced at $24,932 works out to about $2.71 per watt.
This single number cuts through nearly every sales trick. The U.S. average is roughly $2.58 per watt before incentives, and a 12 kW system runs around $30,505 at that rate. Cash deals from reputable installers often fall between $2.50 and $3.00 per watt. Well above that, you are paying for sales overhead or a financing markup baked into the price. Well below it, ask hard questions about equipment and who is actually doing the install. EnergySage's cost data also shows that the panels themselves are only about 12 percent of total system cost, so a "premium panel" upsell rarely justifies a large jump in price per watt.
Equipment Tier and Warranties
Proposals love to list brand names. What you want is the warranty behind them, and there are two separate ones that people constantly confuse.
The equipment warranty comes from the manufacturer and covers the hardware itself. Panels are commonly warrantied for around 25 years, and many include a production guarantee promising the panel still makes a set percentage of its rated output decades out. Inverters typically carry 10 to 25 year coverage, and inverters are the part most likely to need replacing first. The workmanship warranty comes from the installer and covers their labor, the roof penetrations, and the wiring they did. Workmanship coverage varies a lot by company, from one or two years to ten or more.
Here is the trap. A premium panel with a 25-year warranty means little if the installer offers a one-year workmanship warranty and a roof leak shows up in year three. Consumer Reports flags installer track record and warranty length as a bigger predictor of satisfaction than the panel brand on the box. Read both warranties, write down both numbers, and ask who you call when something fails after the company that sold it to you is gone.
Net Cost After the 30% Credit
The 30% Residential Clean Energy Credit is real and large, and it is also widely misrepresented in proposals. It is a federal tax credit. You claim it when you file, and it reduces what you owe the IRS. It is not a discount the installer applies at signing, and it is not a check that lands in your mailbox in week one.
On a $24,932 system, the credit is about $7,480, bringing net cost to roughly $17,452 for a buyer with enough tax liability to use it. The IRS rules let you carry forward unused credit to future tax years, but you need the liability to claim it at all. A proposal that shows only the post-credit number, with no gross price and no note that the credit depends on your taxes, is hiding the real cost. Always find the gross price and compute the credit yourself.
Financing Terms and the Dealer Fee Trap
This is where the low monthly payment usually hides its cost. Solar loans often carry a dealer fee, sometimes 15 to 30 percent of the loan, that buys down the advertised interest rate. The fee gets folded into the system price, so the same panels on the same roof cost thousands more on a low-rate loan than they would in cash. EnergySage's loan guidance walks through exactly this: a lower rate with a high dealer fee can cost more than a higher rate with no fee.
When you read the financing section, find the cash price and the financed price and compare them. Ask for the APR, the term in years, the dealer fee as a dollar amount, and whether the payment assumes you re-amortize after applying your tax credit. A payment that jumps in month 18 because you did not hand the credit back to the lender is a surprise nobody should sign into blind.
The Proposal Checklist
Run every quote through the same list. If a line is missing, that is your first question for the installer.
- System size stated in kW of DC capacity.
- Year-one production in kWh, with the modeling assumptions named.
- An annual degradation rate applied to future production.
- Gross price before any incentive, shown clearly.
- Price per watt, or enough to calculate it.
- The 30% federal credit shown as a tax credit, not a rebate, with gross price visible.
- Net cost after the credit.
- Panel and inverter equipment warranties, in years.
- Installer workmanship warranty, in years.
- A production guarantee, if one is offered, with the percentage and term.
- Financing APR, term, and dealer fee as a dollar figure.
- Total panel count, model, and inverter type.
Red Flags in a Proposal
Some of these are sloppy. Some are deliberate. All of them are reasons to slow down.
- Only a monthly payment. No kW, no kWh, no cash price. The single biggest tell.
- The credit shown as instant money. If the proposal subtracts 30% as if the installer pays it, they are misstating how the credit works.
- Production with no method. A round kWh number and no mention of sun hours, derate, or degradation.
- Today-only pricing. A discount that vanishes if you do not sign on the spot. Real systems do not expire at midnight.
- A blended warranty. One warranty figure that does not separate equipment from workmanship.
- Price per watt far above $3.00 with no clear reason, which usually means a financing markup you cannot see.
Two Quotes, Same Roof: A Worked Example
Back to the two installers. Put their numbers side by side and the low-payment quote stops looking like a deal. The table below maps the same line items from a proposal that shows its work against one built to sell a payment.
| Line item | Proposal that shows its work | Payment-first proposal |
|---|---|---|
| System size | 9.2 kW, 23 panels listed | "Right-sized for your home" (no kW) |
| Year-one production | 13,400 kWh, model and derate named | Not shown |
| Gross price | $24,932 | Not shown, only $129/mo |
| Price per watt | $2.71/W | ~$3.40/W once you back it out |
| Federal credit | $7,480, labeled a tax credit | "30% off" applied as instant discount |
| Equipment warranty | 25 yr panel, 25 yr inverter | "25-year warranty" (blended) |
| Workmanship warranty | 10 years | Not stated |
| Financing | Cash price and financed price both shown | Dealer fee folded in, not disclosed |
The payment-first quote is not cheaper. It is more expensive, dressed as less. Backing out its price per watt puts it well above the honest quote, and the gap is the hidden dealer fee plus sales overhead. Notice too that the honest quote tells you what it will produce, so you can check the savings claim against your own bills. The payment-first quote asks you to trust a number you cannot verify, which is the whole point of leaving production off the page.
This is the problem Enact set out to fix on the homeowner side. Instead of a sales-driven sketch, Enact builds proposals from your actual roof and meter data with line-item assumptions you can see, so production, price per watt, and net cost are all on the page rather than buried behind a payment. If you are comparing offers and want a baseline built on real numbers, the residential solar tools give you a reference to hold each quote against. When every proposal has to show the same line items, the honest one wins on the math, not the pitch.
Frequently asked questions
What should a solar proposal include?
At minimum, a solar proposal should state system size in kW, year-one production in kWh, the gross price before incentives, the price per watt, the 30% federal credit shown as a tax credit, net cost after the credit, and both the equipment and workmanship warranties. The DOE homeowner guide recommends collecting several bids with these items so you can compare them line by line.
How do I compare two solar quotes that look different?
Convert both to price per watt by dividing the gross price by the system size in watts, then compare year-one production for the same roof. That puts different-sized systems on one scale. The U.S. average is about $2.58 per watt before incentives, so a quote far above that range usually carries a financing markup.
Is the 30% solar tax credit money the installer pays me?
No. The 30% Residential Clean Energy Credit is a federal tax credit you claim when you file, and it reduces what you owe the IRS rather than arriving as a rebate. Per the IRS rules, you need tax liability to use it, though unused amounts can carry forward to later years.
What is a good price per watt for solar?
Cash installs from reputable companies often land between $2.50 and $3.00 per watt before incentives, against a national average near $2.58 per watt. Prices well above $3.00 with no clear reason usually mean a dealer fee or sales overhead folded into the system cost.
Why is the financed price higher than the cash price?
Many solar loans add a dealer fee, often 15 to 30 percent of the loan, that buys down the advertised interest rate and gets folded into the system price. As EnergySage explains, a low rate with a high dealer fee can cost more overall than a higher rate with no fee, so always compare the cash and financed prices.
What is the difference between an equipment and a workmanship warranty?
The equipment warranty comes from the manufacturer and covers the panels and inverter, often around 25 years for panels and 10 to 25 for inverters. The workmanship warranty comes from your installer and covers their labor, roof penetrations, and wiring, and its length varies widely. Consumer Reports notes that installer track record and warranty length predict satisfaction more than the panel brand.
Sources
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