How to Write a Solar Proposal: Complete Guide (2026)

A solar proposal that closes the job answers three things fast: what system you're installing, what it will produce, and what it costs over time compared to the customer's current utility bill. The strongest proposals lead with a load-matched system design, show production estimates in kWh not just panel count, lay out financing or cash pricing with no hidden adders, and back it up with a clean site survey and equipment spec sheet. Skip the filler pages. Homeowners read the first two pages and the price. Everything else is proof.

Start with the site data, not the template

Every proposal worth sending starts with a real site visit or a remote shade analysis pulled from satellite imagery and a utility bill history. If you're still building proposals off a rough Google Earth guess and a gut-feel panel count, you're going to get challenged on production numbers, and you'll lose that argument in front of the customer.

Pull at least 12 months of utility usage if the homeowner can get it, ideally broken down by month so you can size for winter heating loads or summer AC spikes. Note roof pitch, azimuth, and any shading from trees, chimneys, or neighboring rooflines. Run a shading analysis with a tool like a Solar Pathfinder or a phone-based irradiance app, and record it. That data point alone separates a serious proposal from a sales flyer.

Design the system to the load, not the roof

A common mistake is designing to fill available roof space instead of matching annual consumption. Oversizing burns budget and inflates the price for no real benefit under most net metering or net billing tariffs. Undersizing leaves the customer disappointed when their bill doesn't drop the way they expected.

Show your math: annual kWh usage, offset percentage you're targeting (most residential jobs land somewhere in the 80% to 100% range depending on the utility's export compensation), and how many modules and what inverter configuration get you there. If you're using string inverters versus microinverters versus a hybrid inverter with battery-ready DC coupling, explain why in plain language. Homeowners don't need to understand MPPT tracking, but they should understand why you picked the setup you did.

Break down equipment like a real spec sheet

List the actual module make, model, and wattage. List the inverter brand and model, whether it's string, micro, or hybrid. If a battery is part of the scope, name the chemistry (most current residential batteries are lithium iron phosphate) and usable capacity in kWh, not just the marketing name.

• Module count, wattage, and total DC array size in kW
• Inverter type, brand, and AC output rating
• Battery model, usable kWh, and round-trip efficiency if the homeowner asked for backup power
• Racking system and attachment method (rail-based, shared rail, or ballasted for flat roofs)
• Conduit routing and where the main service panel or subpanel work falls

This level of detail does two things. It protects you if a customer shops your proposal against a competitor's vaguer one, and it gives your crew a document they can actually build from instead of a sales PDF full of stock photos.

Show production estimates with real assumptions

Every serious proposal includes a first-year production estimate in kWh, usually generated through a tool like PVWatts or your design software's built-in modeling engine. Show the assumptions: system size, tilt, azimuth, shading derate, and an inverter efficiency factor. Don't just print a single number and call it done.

Include a degradation assumption for module output over time (most crystalline silicon panels are rated for a slow annual decline, often in the range of a few tenths of a percent per year, per manufacturer warranty documents) so the customer understands year-one production isn't the number they'll see in year twenty. This is also where you set expectations on inverter clipping if the DC-to-AC ratio is oversized, and on regional weather variance from year to year. A homeowner who understands why production swings 10% to 15% year over year based on cloud cover won't call you in a panic after a rainy summer.

Price it clearly: cash, loan, and lease/PPA side by side

Most homeowners are comparing three payment paths: cash purchase, a solar loan, or a lease/power purchase agreement (PPA). Lay all three out side by side if you offer them, with monthly payment, term length, and what happens at the end of the term.

On the tax side, be precise and current. The 30% federal residential solar tax credit for owned systems ended December 31, 2025. For any proposal you're writing now, do not present that credit as available to a homeowner who purchases or finances the system with a loan. If you offer a lease or PPA, the underlying tax benefit may still flow through the ownership entity (the installer or a third-party financier) through 2027 in some structures, and that can show up as a lower monthly rate on the lease side. Don't quote specific percentages or dollar figures on that pass-through benefit unless your finance partner has given you exact, current terms in writing. State it as "may reduce your monthly payment" rather than promising a number you don't control.

Always show the price per watt for the system as installed, and show it against a rough regional benchmark range so the customer can sanity-check your number against what they've read online. If your price is higher because you're using a better racking system, a tier-1 module, or a longer workmanship warranty, say so directly.

Permitting, interconnection, and inspection timeline

Homeowners routinely underestimate how long the process takes between signing and flipping the system on. Break the timeline into stages: permit submission to the local building department, plan review, installation window, electrical inspection, and utility interconnection agreement or permission-to-operate (PTO) approval. Depending on the jurisdiction and utility, that full cycle can run anywhere from a few weeks to a few months. Set that expectation in the proposal itself, not in a follow-up call after the contract is signed.

If your jurisdiction requires a structural engineer letter for roof-mounted arrays, or if the utility has a specific interconnection application process with its own queue times, mention it. It shows the homeowner you've done this exact job before in their area, which matters more than any glossy rendering.

Warranty terms in plain language

Separate the three warranty types clearly: manufacturer product warranty on the modules, manufacturer or third-party warranty on the inverter, and your own workmanship warranty on the installation. Homeowners often assume a 25-year panel warranty means 25 years of full coverage on everything, including your labor if a roof penetration leaks. Spell out what your workmanship warranty actually covers and for how long, and note whether it's transferable if the home sells.

Format it so it reads fast

A proposal that takes 20 minutes to read loses deals to one that takes five. Front-load the summary: system size, estimated production, estimated bill offset, price, and monthly payment options on page one. Push the full equipment spec sheet, site photos, shading analysis, and warranty language to later pages as backup documentation. Most homeowners decide based on the first page and the price. Give them a reason to trust the rest by making sure the numbers on that first page tie out exactly to the detail pages behind it.

Building these by hand in a general document editor eats hours you could spend on the roof or in front of the next customer. Solar proposal software built for this trade, like try it free, pulls utility data, runs the production model, and formats the spec sheet and financing comparison automatically, so your crew's time goes into the install instead of the paperwork.

Frequently asked questions

How long should a solar proposal be?

Most effective residential proposals run somewhere between four and ten pages: a summary page up front with system size, production estimate, and pricing, followed by equipment specs, a site or shading analysis, financing comparison, and warranty terms. Longer than that and homeowners stop reading past the price page.

Do I need to include a shading analysis in every proposal?

Yes, on any roof with trees, adjacent structures, or dormers that could cast shadows during peak sun hours. Even a simple photo-based or app-generated shading report protects you from production disputes later and shows the homeowner you didn't just eyeball the roof from the driveway.

Can I still mention the 30% federal tax credit in a proposal?

Not for a customer purchasing or financing the system with a loan after December 31, 2025, since the residential credit ended on that date. If you offer a lease or PPA, a related tax benefit may still apply through the financing entity through 2027 in some structures, but present that as something that may lower the payment, not as a guaranteed dollar figure or percentage owed to the homeowner.