A solar design proposal is the single most important document you will see before you sign a contract, and it is also the one most homeowners skim. It is easy to jump straight to the price and the estimated savings, but the numbers on the last page only make sense once you understand the design that produces them. A proposal tells you exactly which panels go on your roof, where each one sits, how much sun each will get, and how much power the whole system should make in a year. Learn to read those four things, and you can tell a careful, site-specific design from a template someone dropped your address into. This guide walks through each section in plain language.
What a solar design proposal actually is
A design proposal is the engineering picture of your future system translated into something a homeowner can review. It is not a marketing brochure, and it is not just a price sheet. A complete proposal shows the equipment, a to-scale layout of the panels on your actual roof, a shading study, and a production estimate tied to your energy use. When those pieces agree with each other, you are looking at a real design. When the layout is a generic rectangle, and the production number is a round figure with no shading study behind it, you are looking at a sales estimate wearing a design’s clothing.
The difference between a proposal and a price quote
A price quote answers one question: what will this cost? A design proposal answers a harder set of questions about what you are actually buying and why it will perform the way the seller claims. The two often arrive stapled together, which is why buyers confuse them. Read the design first and the price second, because the design is what justifies the price. If you want the full argument for why this matters, it helps to understand why a custom design beats a generic one before you weigh any single proposal.
The four sections every proposal should have
Every trustworthy proposal contains four readable parts: a panel and equipment specification, a roof layout diagram, a shading or solar-access analysis, and a production estimate compared against your annual usage. If any of the four is missing, that is the first thing to ask about. The rest of this guide takes them one at a time.
Reading the panel specifications
The equipment section is where the proposal names the exact hardware. Look past the brand logos and find four numbers: the panel model, the wattage per panel, the number of panels, and the resulting system size in kilowatts.
Wattage, count, and total system size
System size is simply panel wattage multiplied by the number of panels, divided by 1,000. A design of 20 panels rated at 425 watts each is an 8.5-kilowatt system. This matters because the size should be driven by your energy use, not by how many panels happen to fit on the roof. If the proposal sizes the system far above your annual consumption without explaining why, ask what assumption is behind it, because oversizing under current export rules rarely pays off. The equipment you pick drives most of the system price, so the spec sheet and the cost page should tell a consistent story.
Efficiency, brand, and warranty terms
Efficiency describes how much of the sunlight hitting a panel becomes electricity, and higher efficiency lets you fit more capacity on a limited roof. Two proposals can quote the same system size while using very different panels, so check the module efficiency and the two warranties that come with it: the product warranty on the hardware and the performance warranty on output over 25 years. A proposal that names the exact model lets you verify these yourself. A proposal that says only “premium panels” is hiding the one detail you most need.
Understanding the layout diagram
The layout diagram is the part most homeowners glance at, and few actually read, yet it reveals whether the design was built for your roof or copied from a template.
Roof planes, azimuth, and tilt
Your roof is made of planes, and each plane faces a direction and sits at an angle. Azimuth is the compass direction a plane faces, and tilt is its slope. In the northern hemisphere, south-facing planes produce the most, west-facing planes shift production toward the evening, and north-facing planes produce the least. A real design places panels across the planes that make sense and explains why, drawing on how a design engine segments your roof into planes from aerial imagery. If every panel sits on one rectangle with no nod to your roof’s real shape, the design skipped this step.
Why panel placement is not just about fit
Good placement respects fire-code setbacks, keeps panels clear of vents, chimneys, and valleys, and groups them to match how they are wired into strings. Placement also decides how the array looks from the street, which matters to many owners. On an irregular or multi-plane roof, reading the layout carefully is even more important because the difference between a thoughtful plan and a lazy one shows up as real lost production over the system’s life.
Making sense of the shading analysis
Shading is the quiet variable that separates an optimistic estimate from an honest one. A panel in shade for part of the day produces less, and a good proposal measures this rather than assuming a clear sky.
Solar access and the shade percentage
Many proposals report a solar-access figure, sometimes shown as a percentage for the whole array or for each panel. A value near 100 percent means almost no shading across the year, while a lower number means a tree, a neighboring roofline, or a chimney is blocking sun during part of the day. The number should come from a real analysis of obstructions around your home across the seasons, not a blanket assumption. Because a remote study has limits, it helps to know what an automated tool can and cannot tell you, so you can judge how much confidence the shading figures deserve.
Per-panel production and why it varies
The best proposals show production for each panel or each zone, not just a single system total. This is where shading becomes concrete: a panel under a tree in the afternoon might show noticeably lower output than its neighbor ten feet away. Per-panel numbers also justify design choices like module-level electronics, which let a lightly shaded panel underperform without dragging the rest of the array down. If a proposal reports one average and hides the spread, you cannot see where the shade is costing you.
Checking production estimates against your usage
The production estimate is the payoff of the whole design, and it only means something when you compare it to your own consumption.
Annual kWh and offset percentage
The proposal should state an estimated annual production in kilowatt-hours and an offset percentage, which is the share of your yearly electricity use the system is expected to cover. Pull out a recent utility bill or a full year of usage and check the math yourself. An offset near 100 percent aims to cover your current use, while a lower figure leaves part of your bill on the grid. Neither is automatically right, but the proposal should explain which target it chose and why.
How NEM 3.0 changes what a good design looks like
Under California’s current net-metering rules, power you export to the grid is worth far less than the power you use at home the moment you make it. That reshapes what a strong design looks like: covering every kilowatt-hour on paper matters less than producing power when you actually use it, and pairing solar with a battery often does more for your bill than simply adding panels. Reading the estimate alongside rising utility rates and how export credits are valued now tells you whether the design was built for today’s rules or last decade’s.
Red flags and questions to raise
Once you can read the four sections, the weak proposals give themselves away. A few patterns should slow you down before you sign.
Signs that a design was not customized
Watch for a layout that ignores your roof’s real shape, a shading study that is missing or reports a suspiciously perfect number, a system size that does not match your usage, and vague equipment described only as “high efficiency.” Each of these is a symptom that a template was filled in rather than a design built. For a fuller list, review the red flags that a design was never customized to your home and check your own proposal against it.
Questions worth asking before you sign
Ask why the system was sized the way it was, what the solar-access figure is for the shadiest panels, which exact panel model and inverter you are getting, and how the production estimate accounts for shading and your real usage. A confident designer answers these in a sentence each. Hesitation or a change of subject is its own answer.
How Axia Solar builds a proposal you can actually read
Axia Solar was built so the design comes first and the sales pitch comes second. Our platform models your specific roof from aerial imagery, segments it into planes with their real azimuth and tilt, runs a shading analysis across the year, and sizes the system to your actual usage under current net-metering rules rather than to a round-number target. The proposal you receive names the exact equipment, shows the panel-by-panel layout and production, and lays the shading study out where you can see it. The goal is a document you can read and question, not one you are asked to trust on faith.
Reading between the panels
A solar design proposal rewards the few extra minutes it takes to read it properly. The equipment section tells you what you are buying, the layout shows where it goes and why, the shading study reveals how much sun it will really see, and the production estimate ties all of it back to your own bill. When those four sections agree with one another and with your usage, you have a design worth trusting. When they do not, you have found the questions to ask before any money changes hands. When you are ready for a design built to be read this way, you can request a custom solar design and check every section for yourself.
Frequently Asked Questions
What is a solar design proposal?
A solar design proposal is the engineering picture of a proposed system, presented for a homeowner to review. It contains the panel and equipment specifications, a to-scale layout of the panels on your actual roof, a shading or solar-access analysis, and a production estimate compared against your annual energy use. It is different from a price quote, which only states cost. The design is what justifies the price, so read it first.
What should a solar design proposal include?
A complete proposal has four readable parts: the exact equipment specification with panel model, wattage, count, and system size in kilowatts; a roof layout diagram showing panel placement across your roof planes; a shading analysis reporting solar access for the array or each panel; and a production estimate in annual kilowatt-hours with an offset percentage tied to your usage. If any of the four is missing, ask why before you go further.
What does the shading analysis in a solar proposal mean?
The shading analysis measures how much sunlight your panels will actually receive once trees, chimneys, and nearby rooflines are accounted for across the seasons. It is often shown as a solar-access percentage, where a value near 100 percent means very little shading. The best proposals report this per panel or per zone rather than as a single average, so you can see exactly where shade is reducing production.
How do I know if my solar system is sized correctly?
Compare the estimated annual production in the proposal to your own yearly electricity use from a full year of utility bills. The proposal should state an offset percentage showing how much of your use the system is expected to cover, and it should explain the target it chose. Under current net-metering rules, sizing to match when you use power, often with a battery, can matter more than covering every kilowatt-hour on paper.
What is the difference between a solar proposal and a solar quote?
A quote answers what the system will cost. A proposal answers what you are buying and why it will perform as promised, through the equipment specification, layout, shading study, and production estimate. The two often arrive together, which is why they get confused. Read the design proposal first, because it is the design that justifies the price in the quote.
How can I tell if a solar design was customized to my roof?
Look for a layout that follows your roof’s real shape and planes, a shading study with a specific solar-access figure rather than a perfect round number, a system size that matches your usage, and named equipment rather than vague “premium” labels. A layout that is a single generic rectangle, a missing shading study, or a system size unconnected to your bill are signs that a template was filled in instead of a design being built.
