Comparing Solar Production Estimates: A Guide to Navigating Different Tools and Data Sources

Understanding Production Discrepancies When Rebuilding Remote Designs

When moving a project from one remote design platform to another (such as rebuilding an Aurora design within Scanifly Remote or Scanifly On-site), it is common to see variations in the final production estimates.

When you see a difference, it is natural to question which platform is correct. However, because remote data is inherently imperfect, differences are an expected part of the design process before an on-site visit occurs. This guide will help you understand why these differences happen, how to establish an acceptable baseline, and when a discrepancy warrants a deeper look.

The Reality of Remote Data: Manual Modeling & Layers

Remote design is a powerful starting point, but it relies on an interpretation of the property. Because no one has visited the physical site yet to collect the most updated, accurate information, remote tools require a designer to manually construct the scene.

When rebuilding a design, variations happen because:

Manual Scene Recreation: A designer must manually place shading obstructions, trees, and roof features based on their individual interpretation of the site. Two different designers might model the exact same tree with slightly different heights or canopy densities.
Conflicting Data Layers: Remote platforms pull from various 2D imagery and 3D LiDAR layers. Depending on when those layers were captured or how a software engine processes them, minor structural differences can occur.

Note: Ultimately, remote design is an estimate of a simulated environment. True precision is unlocked once high-resolution, on-site drone data or manual measurments are captured.

The +/-5% Rule: When Should You Investigate?

Within +/- 5%: If your Scanifly Remote estimate is within 5% of your original remote design, no action is needed. This is considered a comparable and acceptable variance between two remote modeling engines.
Beyond +/-5%: If the discrepancy is greater than 5% (higher or lower), it is worth diving into the data to spot the difference or reaching out to our team for an audit.

The "Spot the Difference" Audit Checklist

If you have a discrepancy larger than 5%, use this checklist to compare the specific inputs of both designs. Often, a major production swing comes down to a few mismatched settings.

If you would like to use this template, please use this link: Google Sheet - Solar Production Comparison

Tip: If you are comparing a simple, south-facing roof with zero shade, almost any discrepancy is going to be driven by the Simulation Engine or System Losses. However, if you are working with a highly cut-up roof, dormers, or heavy tree coverage, variations in Manual Scene Recreation (how the user drew the 3D environment) are usually the primary cause of the difference.

1. Project Basics

Scanifly Project Name & Project Link: Confirm exact Project Addresses match & the property is the same.

2. Geometry & Environmental Values

Roof Planes, Pitch, & Azimuth: Do the roof slopes and orientations match exactly? A few degrees of difference will alter production.
Shading Coefficients (ASA / TSRF): Check the specific shade values applied to the modules.

3. Equipment & Hardware Profiles

PV Module Model & Quantity: Ensure the exact same module profile and count are used.
Inverter Model: Verify the Scanifly simulation settings match the inverter/array ratio as the Aurora inverter selection, as different engines calculate clipping and efficiency curves uniquely.

4. System Losses & Derates

The "Hidden" Variables: Look at the fine print for soiling, snow, wiring, and age degradation.
Shade Loss Factors: Isolate the exact monthly vs. annual loss factors used in the original simulation.
Simulation Engine Version: Verify which calculation engine the other platform uses.
- Scanifly utilizes NLR/NREL’s PVWatts v8—the most current standard. Some legacy platforms still run on deprecated versions (like PVWatts v6), which can cause unexpected difference in production.

💡 Support Tip: Some design platforms make specific system loss and derate data difficult to find in their standard proposal views. You may need to export a full shade or simulation report to uncover the exact percentages being applied.

How to Handle Next Steps

If you have gone through the checklist and the designs still don't align, don't waste time going down a rabbit hole trying to force the math to match.

Option 1: Request a Scanifly Audit. Reach out directly to our support team with your Scanifly project link and a copy of the alternative design or shade report. We will gladly run a side-by-side audit with you to identify the exact technical driver of the variance.
Option 2: Transition to On-Site Reality. Remember that the ultimate source of truth is an on-site drone scan. If a remote design feels uncertain, moving the project to an on-site workflow will eliminate the guesswork and provide an indisputable 3D model of the property.