What Is TSRF (Total Solar Resource Fraction)?
TSRF, short for Total Solar Resource Fraction, is a single score showing how much of the ideal solar resource a specific roof location actually receives once its direction, tilt, and shading are all counted. A higher score means the spot is closer to a perfectly oriented, unshaded array.
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TSRF, short for Total Solar Resource Fraction, is a single score showing how much of the ideal solar resource a specific roof location actually receives once its direction, tilt, and shading are all counted. A higher score means the spot is closer to a perfectly oriented, unshaded array.
TSRF (Total Solar Resource Fraction) explained
TSRF combines two ingredients. Solar access captures how much sunlight survives the shading from trees, buildings, and roof features through the year. The tilt and orientation factor captures how far the surface sits from the best direction and slope for that location. Multiply them and the result is stated as a share of the ideal. A spot with no shade and a strong orientation scores near the top, while a shaded west slope scores much lower.
Setters will almost never calculate TSRF, but the score shows up downstream. Some incentive programs and some ownership providers set a floor for how much of the resource a site must receive, and design teams use the score to decide which roof planes get panels. That is one reason an appointment that sounded fine on the phone can fall apart at the design stage, after the homeowner has already invested time and hope.
TSRF is easy to misuse. It describes a location, not a panel brand or a whole system, so one roof can carry several scores. Nor is it a plain shade percentage, because orientation is built in. And it depends on how the shading was measured: a quick satellite estimate and an on-roof reading can disagree, so an early number should be treated as a draft until the site visit confirms it.
Why it matters when you're buying
A roof that fails a resource threshold costs everyone time: the homeowner, the closer, and the install team. Setters cannot calculate TSRF, but they can ask about trees, neighboring buildings, and which way the roof faces, and write down what they hear. Clean notes at the start mean fewer deals that die quietly after design review.
Frequently Asked Questions
What is a good TSRF for solar?
Is TSRF the same as solar access?
How is TSRF measured?
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