Sales proposals almost always leverage data from satellite or remote imagery, but there’s a problem. Solar surveyors and designers overwhelmingly report satellite imagery is not fully accurate and needs to be verified on-site.

However, just saying “satellite imagery is inaccurate” leads to other questions:

What’s inaccurate about it? How accurate is “good enough”?
What happens if I use inaccurate data?
Why shouldn’t I use preliminary designs for installation planning?

Three distinct variables impact a project's profit margins, the team's capabilities, and time to completion.

1. Sizing the System

Let’s say a sales rep can squeeze 20 panels on a roof in a preliminary proposal, based on a quick satellite snapshot. Since satellite data can have an inaccuracy delta of 10%+, the roof might only be able to hold 17 or 18 panels in the end—this is a significant change in electrical bill offset that could upset a customer.

That delta might also be impacted by technology. The proliferation of cheap and free quoting tools in solar means the quality of preliminary designs has gone down even further. So, that 20-panel estimation might drop to 14 or 15, making it a considerable change and adding proverbial insult to injury.

2. Production Estimates (and Guarantees)

Inaccuracy from satellite imagery or quoting tools will likely cause a production delta. But many preliminary designs also don’t fully consider obstructions, trees, or other shading implications. This means even if a panel will fit in a section of the roof, it might actually be covered by shading, reducing production even more than expected. This would upset the homeowner, and yield further trouble if there is a production guarantee.

While you may be able to upsize the system and add more panels, this makes the system far more expensive for homeowners. Ultimately, this can seriously damage your reputation in the market because you’ll be perceived as a contractor who doesn’t know how to survey correctly.

3. Hardware Costs

From the time you do a preliminary design to making an installation plan and buying materials, prices could change. Or you could face supply issues and be forced to use different hardware materials. Or the homeowner will make specific requests (like changing the array design for aesthetics) that will impact how much material you need for the job.

Even if it’s only a few weeks in between to get permits, that’s enough time for issues to arise. And if you base everything on the preliminary design, you might be on the hook for those extra costs.

Advice for Contractors When Creating Preliminary Designs

While you should never rely solely on preliminary designs for installations, they still have their place in an efficient project workflow. Doing truck rolls for preliminary designs is costly and time-consuming, so we advise not to ignore satellite imagery entirely.

To cover yourself and ensure you don’t anger customers, consider these three things.

1. Set expectations: have your sales reps explain that you can get them a quick preliminary design, but it may not consider every small detail that could impact the system. Share how the preliminary design is meant to give homeowners an idea of what could be possible, but not guarantee anything—you’d need to verify onsite for that.

2. Explain context: homeowners will likely wonder why you’re using a preliminary design if it isn’t fully accurate. Explain to them that the preliminary design is about getting them the information quickly so they can have a sense of the project details. In short, it’s an introduction and first step rather than charging them significant amounts upfront to get everything technically perfect.

3. Ensure comprehensive and accurate survey measurements: when you eventually go on-site, measure every roof plane and capture the entire site. Then, model out potential issues like obstructions and shading. If there are significant changes between the preliminary and final designs, communicate the reasons to homeowners so they know it’s not you tricking them but legitimate problems you’re trying to work around.

The Optimal Solution: Combine Your Remote and On-site Data On One Platform

We’ve explored the shortcomings of using only your remote design or quoting tool for installation planning, but we know everyone needs preliminary design software. The issue? They all use the same data and claim to be “accurate” enough for final layouts.

Good news for contractors. There’s now a better way - integrating your remote and on-site data to design perfect PV systems for every project. Platforms like Scanifly now enable you to combine the speed of a remote design with the precision of a drone-based final layout on one platform. No more toggling between or paying for multiple tools to get the highest level of accuracy.

This integration is pivotal in achieving precision and efficiency from prelim to PTO. Here, we explore the significant benefits of this hybrid approach, ensuring optimal design and installation outcomes.

1. Holistic site assessment: Merging your remote and on-site data provides a comprehensive view of the project site. Remote data gives sales teams an understanding of site viability, while on-site visits provide detailed measurements and insights into specific environmental factors. This holistic assessment ensures your design is tailored precisely to each site's unique real-time conditions, accounting for different seasons, new construction, etc.

2. Enhanced accuracy in sizing and placement: Remote data, often in the form of satellite imagery, offers an initial estimate of the potential solar panel layout. However, integrating on-site data can significantly refine this estimation. On-site evaluations allow for the accurate measurement of roof planes, shading patterns, and other critical factors, leading to a more exact determination of panel placement and project size in your final plan sets.

3. Realistic production estimates: While remote data provides a baseline for potential kWh production, on-site assessments offer a reality check, considering obstructions like trees or nearby buildings. This combination makes certain the design includes realistic production estimates, which is crucial for setting customer expectations, upholding your solid reputation, and delivering high-quality PV systems.

Own the Design, Own the Customer Relationship

Whether your company does its own sales or buys leads from a sales-only outfit, the reality is doing the final design and installation is key to building a strong customer relationship. While the preliminary design can excite customers about the prospect of solar, the final design ultimately goes on their house, so they need to understand it fully.

This opens an opportunity for solar sales reps, surveyors, and designers to work together in a more collaborative way. It’s in everyone’s best interest to deliver the best (and biggest) possible system to homeowners, but only if it is functional, can deliver on production and offset, and looks good. A finished product is your calling card and the best possible billboard advertisement, so the whole team needs to work together to deliver high-quality service.

3 Reasons You Need Remote + On-Site Data For Install Planning