What is your method for placing solar panels?

3 considerations for rooftop solar panel installation

When installing solar panels, Lumen takes into account the shade cast by a building’s structures, electrical or mechanical interaction points that need to be easily accessible, and walkways that need to be traversed freely.


Solar panels make the most energy when they’re in direct sunlight, so we avoid putting them in areas that are routinely shaded. It’s important to note the sun’s interaction with a building when deciding the best locations for installation and how this tango evolves throughout the day or year.

From the top down, it’s often difficult to see vertical shade-casting structures. For example, consider the oblong structure in the center of this roof:

The image above was taken from space when the sun was directly overhead. The structure is casting shade only from its northernmost edge, so most of the roof appears unshaded and solar-panel friendly. However, the sun is directly overhead for only part of the day and hangs low in the sky during winter months.

From this angle, one can see how tall the structure is relative to the length of the roof deck where solar would go:

The structure is going to cast lots of shade in mornings and afternoons. Here’s how the shade looks during that time, along with our simulated recommendation for solar panel placement:

Here’s what the simulation looks like from an angle:

Solar simulation software accounts for shading that happens intra-day and throughout the year as we travel around the sun (the shadows are longer when the sun is lower in the sky, here in the northern hemisphere). We avoid putting panels where they’re going to be so shaded that they drag down the system’s energy productivity, thus financial productivity.

Systems with strong economics have a higher tolerance for shading. For example, in San Diego, where utility rates are very high, even a sub-optimally productive solar panel still yields commercially beneficial savings. For systems with less strong economics, we’d remove such sub-optimal panels to keep the economics looking good.


HVAC equipment, walls, roof edges, window washing fasteners — we need to leave some distance between them and the solar array. We call these distances setbacks. Sometimes they’re required by building code, other times we simply want to leave room to allow humans to move about the roof safely and without threat of physical harm or damage to equipment.


We don’t put solar panels on walkways because walkways are for humans. There are two kinds of walkways. Here’s a rooftop with lots of walkways, clearly marked…

…which looks like this when there’s solar on it:

The other kind of walkway is to give fire fighters a clear path to move quickly across a rooftop:

Bottom Line

Smart solar panel placement is the difference between saving pennies and harnessing the power of the sun for profit. With Lumen’s data-backed installation recommendations, a building owner can access thousands of dollars of untapped earnings. Lumen uses advanced software and industry expertise to determine the optimal locations for solar panel installation, taking into account shading, setbacks and walkways so building owners can reach their full potential.



More resources

October 25, 2022

ESG is now good business

Environmental, Social, Governance, or ESG, is a measurement and reporting standard commonly used by investors to evaluate how responsibly a company earns its profits. The criteria were first introduced in a 2005 study examining the relevance of environmental, social, and governance factors to asset management and financial performance.

Read more

Is Lumen a solar developer?

Read more

ACT Bid Scoring: Process & Guidelines

The goal of this is to document the specific steps that Lumen Energy (LE) will take upon receiving ACT bids from EPC contractors to evaluate and score the bids submitted.

Read more