Certain zip codes qualify as "energy communities" under federal rules — areas historically tied to fossil fuel employment or meeting other criteria. Systems installed there earn an extra adder on top of the ~30% commercial credit, pushing programs like Propel from 30% off to 39.2% off.
You do nothing to earn this except live where you live. But it changes which program wins for your house — in an energy community zip, prepaid ESA programs get dramatically stronger. It's the first thing I check when running your numbers, and it's why the same system can be priced differently one neighborhood over.