Is Your Solar Quote Accurate? How Proposal Software Shapes Your Estimate (2026)

Is Your Solar Quote Accurate? How Proposal Software Shapes Your Estimate

By Solar Calculator Canada. Published May 26, 2026. 9 min read.

Quick answer: The savings number on a solar quote is a prediction, not a fact. It comes out of design software, and the quality of that prediction depends on two things: how well the software models shading and sunlight on your specific roof, and whether a trained person — not just a salesperson — checked the design. The most accurate residential tools use LIDAR-based shading that has been independently validated. Cheaper or free tools that rely on satellite imagery alone tend to produce wider error margins. This guide explains how to tell the difference, so you can judge any quote you are handed.

Why this matters before you sign anything: Two companies can quote the same roof and promise very different savings. Usually the difference is not the panels. It is the software behind the proposal and who built the design. Knowing how these tools work lets you ask the right questions and spot an estimate that is too good to be true.

Every solar proposal you receive contains a predicted first-year production figure, usually in kilowatt-hours, and a dollar savings estimate built on top of it. Nobody measured your roof for a year to get that number. Software estimated it by modelling how much sunlight hits your roof, how much shade trees and chimneys cast, and how your local weather behaves across the seasons.

That means the estimate is only as trustworthy as two things:

• The model. How precisely the software captures shading, roof tilt, orientation, and irradiance on your actual roof, rather than applying a generic regional average.
• The operator. Whether the person who built the design knew what they were doing, and whether anyone with engineering training checked it before it became a promise.

When a savings estimate turns out to be optimistic, it is almost always one of these two failing, not the hardware.

Accuracy tracks closely with the method the software uses to model shade and sunlight. The principle is well established: the US National Renewable Energy Laboratory (NREL) studies remote site assessment precisely because how a tool captures shading drives how reliable its production estimate is. Independent 2026 industry testing groups the methods into rough bands like this:

These bands are drawn from published solar design software accuracy comparisons and should be treated as general ranges, not guarantees. The takeaway holds regardless of the exact figure: a 15 to 20 percent swing on a system that was supposed to cover most of your bill is the difference between a quote that delivers and one that disappoints. The modelling method, not the brand name on the proposal, is the thing to ask about.

Because your return depends on local electricity rates and how you are billed, an inflated production number throws off the entire payback calculation. See our electricity rates across Canada and how net metering works for why the production figure feeds straight into your savings, and our methodology page for how our own calculator estimates production.

We ranked the main tools by what matters for a homeowner-facing residential proposal: how rigorously each models shading and sunlight, whether that accuracy has been independently validated, and how the tool is typically used in the field. This is not a ranking of which tool is "best" in the abstract. A utility-scale engineering tool can be excellent at its job and still be the wrong tool for a home solar quote.

1. Aurora Solar: the residential accuracy benchmark

Aurora Solar is the most widely adopted platform for residential solar design. Its shading engine ray-traces the sun's path for every daylight hour of the year. Aurora states its LIDAR shading values have been validated by the US National Renewable Energy Laboratory (NREL) as statistically equivalent to on-site measurements; the underlying NREL study, funded by the US Department of Energy, found that LIDAR-based remote shading engines came within 3.5 percent of on-site measurements. That validation is strong enough that the New York State Energy Research and Development Authority (a major US rebate authority) accepts Aurora shade reports in place of an on-site visit. If a quote was built in Aurora, the production estimate rests on a model that has been checked against field measurements.

Tradeoff: it is premium-priced software aimed at established installers, which is part of why not every company uses it.

2. HelioScope: engineering-grade, built for commercial

HelioScope, which Aurora acquired in 2021 when it bought maker Folsom Labs, is a simulation-first tool with NREL-validated shading and module-level modelling. It is excellent, but it is optimised for commercial and larger projects rather than polished residential homeowner proposals. Strong accuracy, different use case.

3. PVsyst: the bankable physics standard

PVsyst is the long-standing reference for bankable energy-yield analysis and is often used to validate large projects. It is the most rigorous on the physics, but it has a steep learning curve and does not produce homeowner sales proposals. It is a validation tool, not a quoting tool.

4. Capable mid-tier tools (Solargraf, SurgePV, Pylon, Arka 360)

This group covers residential and light-commercial work with a mix of satellite imagery and, in some cases, LIDAR. They are legitimate, actively developed platforms that can produce solid designs in trained hands. Accuracy varies by how each one is configured and used.

5. OpenSolar: genuinely free, with an accuracy tradeoff

OpenSolar is a fully free, full-featured platform (3D design, shading, proposals, and CRM) that earns revenue through hardware and financing partnerships rather than subscriptions. That open-access model has genuinely helped smaller installers compete, and it deserves credit for that.

The tradeoff is accuracy validation. OpenSolar works from satellite and aerial imagery and does not use advanced LIDAR shading the way Aurora and HelioScope do. Independent 2026 roundups note that, while OpenSolar is the most full-featured free option available, some user reviews report production estimates running noticeably off compared with Aurora or HelioScope, with shading accuracy the most common complaint. For a shading-heavy roof, that is exactly where estimate error creeps in. It is a strong free tool for budget-conscious teams; it is not a tool a homeowner should treat as automatically precise on a complex roof.

The deeper risk is not the software, it is who runs it. A free or low-cost tool in the hands of a trained, supervised designer can produce a reasonable estimate. The same tool in the hands of a commission-driven salesperson, with nobody checking the result, is where inflated savings numbers come from. The fix is not just better software. It is separating the people who sell from the people who verify the design, which is exactly why an independent estimate is a useful check on any installer's quote.

This is the gap an unbiased calculator is built to close. A free Solar Calculator Canada estimate gives you a neutral, transparent baseline that no salesperson has an incentive to inflate. You can then hold any installer quote up against it:

• A neutral baseline. Our calculator uses transparent provincial sun-hour, rate, and incentive data, so you start from a number nobody is trying to sell you. See exactly how we build it on our methodology page.
• A way to sanity-check a quote. If an installer's promised savings sit far above an independent estimate, that gap is your cue to ask which software produced their design and how the shading on your roof was modelled.
• Vetted installers, double-checked numbers. When you are ready, we match you with vetted installers who provide a detailed quote. Comparing that quote against your independent estimate is the simplest accuracy safeguard a homeowner has.

We cannot promise solar will perform identically to any estimate, and no honest tool or installer can, because shading changes, trees grow, and weather varies year to year. What an independent estimate does is make sure you are not relying on a single number from a single party with something to sell.

Before you compare installer quotes, get a neutral baseline. Solar Calculator Canada gives you a free, transparent estimate using provincial sun-hour, rate, and incentive data — no sales pressure, no obligation. Then you can match with vetted installers and hold their detailed quote up against an independent number.

Get your free estimate →

• How We Vet Installers
• Our Calculator Methodology
• Net Metering in Canada
• Electricity Rates Across Canada
• Solar Payback Period
• Best Solar Panels in Canada

1. Aurora Solar, How LIDAR is Transforming Remote Solar System Design (cites the NREL/DOE study on remote shading accuracy)
2. Trina Solar engineering writeup, Aurora shading validated by NREL to within ~3% of on-site measurement
3. US National Renewable Energy Laboratory (NREL)
4. Aurora Solar Help Center, Solar Access and remote shade measurement
5. Aurora Solar acquires Folsom Labs (maker of HelioScope), 2021 press release
6. SurgePV, best solar design software comparison (accuracy bands by modelling method)
7. SPOTIO, best solar design software 2026 (OpenSolar free model and reviewer-reported accuracy)
8. GreenLancer, choosing the best solar design software (OpenSolar monetization model)

This article is for general information only and reflects the solar software landscape current as of May 2026. Software features, pricing, and accuracy validations are set by each vendor and change over time. Accuracy figures are drawn from vendor documentation, independent lab references (NREL), and third-party industry reviews; they are general ranges, not guarantees. Production and savings estimates are predictions, not guarantees, and actual results vary with shading, weather, equipment, and usage.

Solar Calculator Canada is an independent platform connecting Canadian homeowners with vetted solar installers. We do not sell or install solar equipment. Last updated: May 26, 2026.

Why do two solar quotes for the same roof show different savings?

Usually because the two companies used different design software, or modelled shading differently, or one had a salesperson build the design while the other had it engineered and reviewed. The hardware is often similar. The prediction method is what differs.

What is the most accurate solar design software?

For residential proposals, tools that use independently validated LIDAR shading are the most accurate. Aurora Solar states its LIDAR shading is NREL-validated as statistically equivalent to on-site measurements, and the underlying NREL study found LIDAR-based remote shading within about 3.5 percent of on-site readings. Tools that rely on satellite imagery alone typically show wider error margins.

Is OpenSolar accurate?

OpenSolar is a capable, genuinely free platform that many installers use successfully. Its tradeoff is that it works from satellite and aerial imagery rather than advanced LIDAR, and some third-party user reviews report production estimates running off compared with Aurora or HelioScope. On roofs with significant shading, the modelling method matters more, so it is worth asking how any estimate built in it was verified.

Can a salesperson make a solar design?

Technically yes, and in many companies they do. The risk is that a design built by a commission-driven salesperson with no engineering review is more likely to produce an optimistic savings number. Asking who built and who checked your design is one of the most useful questions you can ask.

Why does my solar quote look too good to be true?

Sometimes it is. An estimate built on a regional sunlight average, with no modelling of the trees and obstructions on your actual roof, will read higher than what your roof can really produce. If a quote promises to wipe out your entire bill and the savings look suspiciously clean, ask which software produced it and whether the shading on your roof was actually modelled. Comparing it against an independent estimate is the fastest reality check.

Do solar companies overestimate savings?

Some do, usually not out of malice but because of weak modelling or a salesperson building the design with nobody reviewing it. Optimistic assumptions about shading, sunlight, or future electricity rates all push the savings figure up. The protection is on your side: ask to see the shading map, ask who built and checked the design, and confirm the estimate uses your real provincial rate plan rather than a generic average.

What does LIDAR mean on a solar proposal?

LIDAR is laser-based mapping that measures the real heights of your roof, trees, and nearby buildings to model shade accurately. When a proposal is built with LIDAR shading, the production estimate reflects the actual obstructions around your home rather than a generic assumption. It is one of the strongest signs that a quote is grounded in your specific roof.

Are free solar quotes and free design tools accurate?

A free quote is not automatically inaccurate, and a free tool is not automatically bad. The question is how the estimate was modelled and who checked it. Free platforms often rely on satellite imagery rather than advanced LIDAR, which widens the error margin on shaded roofs. If you get a free quote, simply ask the same verification questions you would ask anyone: what software, what shading method, and who reviewed it.

Why is my actual solar production lower than the estimate on my quote?

A few normal reasons: the estimate did not fully account for shading, the weather in a given year was cloudier than the long-term average, panels lose a little output as they age, and dirt or snow temporarily reduces output. A small gap is normal. A large, persistent gap usually points back to an estimate that was too optimistic at the design stage, which is why the modelling method matters so much before you sign.

Can I trust a solar quote made remotely without a site visit?

Yes, if it was built with validated remote modelling. Independent testing has found that LIDAR-based remote shading can come close to on-site measurements, which is why some US rebate authorities such as NYSERDA accept remote shade reports. A remote quote is not the problem. A quote built on guesswork, whether remote or in person, is the problem. Ask how the roof and shading were measured.

What is the difference between Aurora and OpenSolar?

Aurora is premium paid software widely used for residential design, with independently validated LIDAR shading. OpenSolar is a genuinely free platform that many installers use, but it works from satellite and aerial imagery rather than advanced LIDAR, and some user reviews report wider variance in its production estimates. Both can produce good work in trained hands. The difference that matters to you is whether the estimate on your specific roof was modelled with site-specific shading and then reviewed.

What questions should I ask a solar company before signing?

At minimum: what software produced my design, does it model the shading on my actual roof, who built the design, did anyone with engineering training review it, is the production figure a realistic first-year number, and does the savings math use my real provincial rate plan. Clear answers are a good sign. Vague answers or pressure to sign quickly are not.

Does the salesperson design my solar system?

In some companies, yes, the same person who sells you the system also builds the design, with no independent check. That is where many inflated estimates come from. Ask whether a separate, trained person reviews the design before it becomes a quote, and compare the result against an independent estimate.