By the Solar X Team. Reviewed by the Solar X Engineering Team (ESA/ECRA licensed). Published May 26, 2026.
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 how the software models shading and sunlight on your specific roof, and whether a trained engineer reviewed the design. The most accurate residential tools use LIDAR-based shading that has been independently validated. At Solar X we design in Aurora Solar and have every design reviewed by our engineering team before it reaches you.
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. This guide shows you how the main tools compare and how to pressure-test the number on your own quote.
The Number on Your Quote Is a Model, Not a Measurement
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.
How Accurate Are These Estimates, Really?
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:
| Modelling Method | Typical Production-Estimate Accuracy |
|---|---|
| LIDAR-enhanced shading (laser-measured heights of roof, trees, nearby buildings) | About 3 to 5 percent |
| Satellite or aerial imagery only | About 5 to 10 percent |
| Regional irradiance averages, no site-specific shading | About 15 to 20 percent |
Bands drawn from published solar design software accuracy comparisons. 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.
For Ontario specifically, where your return depends on electricity rates and how you are billed, an inflated production number throws off the entire payback calculation. See our Ontario hydro rates guide and how net metering credits work for why the production figure feeds straight into your savings.
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Solar Proposal Software, Ranked for Residential Accuracy (2026)
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.
Aurora Solar: Residential accuracy benchmark
Modelling Method
LIDAR-enhanced shading, ray-traced sun path
Typical Accuracy
Validated within ~3 to 3.5% of on-site measurement (NREL study)
Best For
Premium residential design and proposal tool
What Solar X uses. Independent engineering writeup confirms Aurora shading within about 3% of on-site measurement.
Tradeoff: Premium-priced, aimed at established installers — not every company uses it.
HelioScope: Engineering-grade, commercial-first
Modelling Method
NREL-validated shading, module-level simulation
Typical Accuracy
Strong, validated
Best For
Commercial and larger projects
Acquired by Aurora Solar in 2021 (Folsom Labs). Excellent for engineering, less polished for homeowner-facing residential proposals.
Tradeoff: Optimised for commercial, not residential sales proposals.
PVsyst: Bankable physics standard
Modelling Method
Rigorous physics-based yield analysis
Typical Accuracy
Industry reference for bankable energy yield
Best For
Validation of large utility-scale projects
Often used to validate large projects. The most rigorous physics, but not a homeowner sales tool.
Tradeoff: Steep learning curve. Does not produce homeowner sales proposals.
Solargraf, SurgePV, Pylon, Arka 360: Capable mid-tier residential tools
Modelling Method
Mix of satellite imagery and, in some cases, LIDAR
Typical Accuracy
Varies by configuration and operator
Best For
Residential and light-commercial
Legitimate, actively developed platforms that can produce solid designs in trained hands.
Tradeoff: Accuracy varies by how each is configured and used.
OpenSolar: Genuinely free, with an accuracy tradeoff
Modelling Method
Satellite and aerial imagery (no advanced LIDAR)
Typical Accuracy
Reviewer-reported variance vs. Aurora/HelioScope, especially on shading
Best For
Free full-featured design + proposals + CRM
Earns revenue through hardware and financing partnerships rather than subscriptions. Helps smaller installers compete.
Tradeoff: Some third-party user reviews report production estimates running noticeably off compared with Aurora or HelioScope. Shading accuracy is the most common complaint.
Aurora's LIDAR shading has been validated against the NREL remote-shading study, as detailed in Aurora's own LIDAR validation writeup and confirmed by an independent Trina Solar engineering article. HelioScope was acquired by Aurora Solar in 2021 (originally built by Folsom Labs). OpenSolar's free-platform model is documented in GreenLancer's overview, and the accuracy-variance complaint is reported in SPOTIO's 2026 design-software roundup.
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.
How Solar X Builds a Quote You Can Trust
We are an Ontario installer, and our process is built to take the two main failure points off the table:
We cannot promise solar will perform identically to any estimate. No honest installer can, because shading changes, trees grow, and weather varies year to year. What we can do is make sure the estimate starts from a validated model and a reviewed design, so the number you sign is realistic rather than aspirational. See how we work in our guide to the best solar companies in Ontario.
How to Pressure-Test Any Solar Quote in 5 Questions
Use these on any quote you receive, ours included:
What software produced this design and estimate?
A confident installer will name it without hesitation.
Does the model use LIDAR or site-specific shading, or a regional average?
Site-specific is what you want.
Who built the design, and did anyone with engineering training review it?
If the only person who touched it was the salesperson, treat the savings number cautiously.
Is the production estimate first-year, and does it account for the trees and obstructions actually on my roof?
Ask to see the shading or irradiance map.
How does the savings figure reflect my Ontario rate plan and billing?
A generic average rate is a red flag.
If a company cannot answer these clearly, the problem is rarely the panels. It is the proposal.
Frequently Asked Questions
Why do two solar quotes for the same roof show different savings?
Usually because the two companies used different design software, 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's shading has been validated against an NREL study to within roughly 3 to 3.5 percent of on-site measurements. 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 heavily shaded roofs the modelling method matters more, so ask 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 a useful question.
What software does Solar X use?
Solar X designs in Aurora Solar and has every design reviewed by its engineering team before it goes to a customer, so the savings estimate is based on a validated shading model and a checked design.
How far off can a solar savings estimate be?
It depends on the modelling method. Validated LIDAR-based tools tend to land within about 3 to 5 percent on production. Estimates built on regional averages with no site-specific shading can be 15 to 20 percent off, which materially changes payback.
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 reads higher than what your roof can really produce. Ask which software produced it and whether the shading on your roof was actually modelled.
Do solar companies overestimate savings?
Some do, usually because of weak modelling or a salesperson building the design with nobody reviewing it. Ask to see the shading map, ask who built and checked the design, and confirm the estimate uses your real Ontario 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. A proposal built with LIDAR shading reflects the actual obstructions around your home rather than a generic assumption.
Are free solar quotes and free design tools accurate?
A free quote is not automatically inaccurate. 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. Ask what software, what shading method, and who reviewed it.
Why is my actual solar production lower than the estimate on my quote?
Common reasons include shading not fully accounted for, a cloudier than average year, gradual panel aging, and temporary dirt or snow. A small gap is normal. A large, persistent gap usually points to an estimate that was too optimistic at the design stage.
Can I trust a solar quote made remotely without a site visit?
Yes, if it was built with validated remote modelling. LIDAR-based remote shading can come close to on-site measurements, which is why some rebate authorities accept remote shade reports. A quote built on guesswork, remote or in person, is the real problem. Ask how the roof and shading were measured.
What is the difference between Aurora Solar and OpenSolar?
Aurora is premium paid software with independently validated LIDAR shading, widely used for residential design. OpenSolar is a genuinely free platform that works from satellite and aerial imagery rather than advanced LIDAR, and some user reviews report wider variance in its estimates. Both can produce good work in trained hands.
What questions should I ask a solar company before signing?
Ask what software produced the design, whether it models the shading on your actual roof, who built the design, whether anyone with engineering training reviewed it, whether the production figure is a realistic first-year number, and whether the savings math uses your real Ontario rate plan.
Does the salesperson design my solar system?
In some companies the same person who sells the system also builds the design with no independent check, which is where many inflated estimates come from. Ask whether a separate trained person reviews the design before it becomes a quote.
Get a Quote Built on a Validated Design
Solar X will design your system in Aurora Solar, model the shading on your actual roof, and have our engineering team review it before you see a number. No obligation, no high-pressure design built on guesswork.
You can also run your own first-pass numbers with the Solar X solar calculator.
External References & Sources
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- 4Aurora Solar Help Center: LIDAR Shadinghelp.aurorasolar.com
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Related Guides
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. Comparative statements reflect publicly reported information and independent reviews; verify current capabilities directly with each vendor. Production and savings estimates are predictions, not guarantees, and actual results vary with shading, weather, equipment, and usage. Last updated: May 26, 2026.
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