Prorate PTC for partial eligibility years - #22
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j-bryan
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Jul 31, 2026
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This change fixes incorrect PTC behavior where a partial final eligibility year would be omitted when building the PTC cashflows.
The main complication in fixing this bug was that some generation objects were created at a particular date but actually referred to generation over the entire year. Since the
Generationclass only accepted adateargument, there was no way to determine what portion of the generation should be included in the PTC payment. Thus,period_startandperiod_endattributes were added toGeneration. Thedateattribute was preserved in order to maintain backwards compatibility and to allow specification of a particular date to use as a basis for other calculations instead of automatically selecting such a date from the applicable period.The period on each
Generationobject is now used to determine overlap between the generation and the PTC eligibility window. This overlap (and the day count convention used for the PTC) determines how the PTC amount is prorated.Tests have been updated and added for these changes, including regression checks to ensure that the full PTC eligibility window is respected.
Closes #18.