How the Solar Site Analyzer works
This tool calls Google’s Solar API — the same dataset behind Project Sunroof — which uses high-resolution aerial imagery and shading models to estimate sun hours, roof area, and the maximum panel layout for residential and commercial buildings. We auto-detect whether your address is a home or a commercial / agricultural building (you can override this), look up the actual electricity rate your serving utility charges that customer class, and hand all of that to Claude AI to write your site assessment. The result is a per-address savings estimate that uses real rates instead of generic national averages.
What the four scores mean
Top-tier solar conditions. Open roof, minimal shading, strong orientation. Most installers will quote a system that pays back in under 10 years.
Above-average sunlight with workable shading. The majority of U.S. homes fall here. Solar is almost always worth quoting.
Workable with thoughtful design — orientation, tilt, and panel selection matter more. Get multiple bids and have installers model the shading.
Heavy shading or unfavorable orientation. Tree removal, ground mount, or a community solar subscription may make more sense than rooftop.
What this tool can’t tell you
- Roof condition. Google can see the shape; it can’t see a 22-year-old asphalt roof that needs replacement before solar goes up. Detach & reset costs add up fast.
- Electrical service capacity. Older 100A panels often need a service upgrade for whole-home solar + future EV charging.
- Your utility’s net metering rules. Net metering rules vary by state and utility. See the basics.
- HOAs and city setbacks. HOAs and city codes can restrict panel placement even on excellent roofs.
- Whether Google has mapped your address. Newer construction and rural parcels sometimes don’t have high-resolution coverage yet. The tool falls back to medium / low quality and reports back if no data is available.
Frequently asked questions
Is the Solar Site Analyzer accurate?
The underlying Google Solar dataset is widely used by the industry and is generally within ~5–10% of what a site survey from a qualified installer will produce for production estimates. It does not account for module-level shading from individual trees that have grown since the imagery was captured, roof age / condition, or your utility’s specific compensation structure. Use it as a starting point, then have at least two installers verify with a real proposal.
How do you detect whether my property is residential or commercial?
We auto-classify using the building footprint from Google’s imagery (homes are typically under 300 m²; commercial / agricultural buildings are usually larger), the maximum panel count your roof supports, and address signals like Suite / Unit / Plaza tokens. The classification appears at the top of your results with a one-click switch if we got it wrong. Property type matters because residential and commercial customers pay different rates and qualify for different incentives.
Where does the electricity rate come from?
Two places, in order. First, we check our own dataset of real customer utility bills that have been parsed line-by-line through our Utility Bill Analyzer — if we’ve seen recent bills for your serving utility in your customer class, we use the median effective per-kWh rate from those (which already includes fuel adjustments, RPS surcharges, and other riders most installer estimates miss). If we don’t have data for your utility yet, we fall back to NREL’s EIA-sourced averages. The card on your results page tells you which source was used.
What if Google doesn’t have data for my address?
About 5–10% of U.S. addresses (mostly rural, newer construction, or buildings with complex geometry) don’t have high-resolution coverage yet. The tool tries three quality tiers (HIGH, MEDIUM, LOW) before giving up. If all three fail, try a neighbor’s address one or two doors down — the sun-hours data is usually within 1% across a single block.
How is the “recommended system size” chosen?
Google returns dozens of panel configurations — from a tiny 4-panel array up to the absolute maximum that fits your roof. We pick the configuration closest to 80% of the maximum panel count. That’s the realistic-install zone for most homes: it avoids cramming panels into low-production corners while still offsetting most of a typical household’s usage.
Continue learning
Roof Fitness for Solar · How many panels do I need? · Solar Panel Cost Guide · Solar Payback Period · Production Estimates