What is the Google Solar API and How Does It Measure Roofs?

The technology behind modern satellite roof measurements isn't magic — it's the Google Solar API, layered with property records and elevation data. Here's exactly what's happening under the hood.

What Is the Google Solar API?

Google launched the Solar API in 2023 as a developer endpoint to support solar panel installation companies. Given any address, it returns:

• Roof segments — every detected facet of the roof with its area, pitch, azimuth, and bounding polygon
• Building footprint — the outline of the building from above
• Solar potential — hours of sun, kWh capacity, optimal panel layout (not relevant for roofing, but it's in the response)
• Imagery date — when the satellite photo was taken (usually within the last 1-3 years)

How Accurate Is It?

For typical residential roofs in covered metro areas, the Solar API hits within 3-5% of in-person measurements. Coverage is best in:

• All major US metros (top 100 by population)
• Most of suburban America
• Sun-belt states (CA, TX, FL, AZ, GA, NC)

Coverage is spotty in:

• Very rural areas with low population density
• Newly constructed homes (imagery hasn't refreshed yet)
• Areas with persistent cloud cover during the satellite pass

Where the Solar API Falls Short (And How RidgeIQ Fixes It)

The Solar API isn't perfect:

• It sometimes returns a fragment — only one facet detected, missing the rest. RidgeIQ catches this by cross-checking against the RentCast property footprint.
• It doesn't always know the pitch — flat roofs and very steep roofs sometimes come back as "unknown." We fall back to elevation-based pitch detection.
• The "best for solar" answer isn't the same as "all roof area" — we use the full building footprint, not just the sunny facets.

What Solar API Doesn't Tell You

It also doesn't return:

• Number of layers (you need to inspect on-site)
• Underlayment type
• Flashing condition
• Ventilation needs

So treat satellite measurement as a "good enough to quote" answer, not a "good enough to start tear-off" answer. The crew still needs to be on the roof before the dumpster arrives.

Why Use It Instead of EagleView?

EagleView still wins on accuracy and insurance acceptance. The Google Solar API wins on speed and cost: 3 seconds vs. 1-4 hours, and effectively free at scale. For the top of the funnel (capturing leads, quoting jobs, qualifying homeowners), speed is way more valuable than the last 1-2% of accuracy.

Want to try it? Punch an address into RidgeIQ — you'll see exactly what Solar API returns, blended with our additional data sources, in under 5 seconds.