What are ASA, TOF and TSRF?

There are many factors that determine how much energy a solar module will produce in a certain location. A module in one location will not produce the same amount of energy as the same module in another location. Furthermore, what if you need to select the optimal roof plane to install the modules. The annual solar access (ASA), tilt and orientation factor (TOF) and total resource fraction (TSRF) data will address these questions.

The Basics: Tilt, Azimuth, & Shade

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Azimuth

The direction your module is facing, orientation / bearing. (Example: South facing roof = 180 degrees Azimuth)

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Shade

How much of the sun is blocked in this location on a yearly basis?

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Tilt

The angle or slope of your surface that you are mounting your modules on. (Example: 8/12 Pitch roof = 34 degree angle = 34 Degrees tilt)

Putting these terms together...

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Annual Solar Access (ASA):

Solar Access is the amount of sun a location receives in a given year, scored out of 100%, with only shade effects factored in.

Example: A solar array in an open field with 10% shade has an Annual Solar Access of 90%.

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Tilt and Orientation Factor (TOF)

TOF is the amount of sun a location receives in a given year, scored out of 100%, with the impact of its Pitch/Tilt factored in.

Example: A solar array facing South has a TOF of 100% (In North America)

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Total Solar Resource Fraction (TSRF)

TSRF is the amount of sun a location receives in a given year, scored out of 100%, with both the TOF and Annual Solar Access taken into consideration.

Example: A solar array facing South with a tree shading 10% has a TSRF of 90%. (100% * 90% = 90%)