It has nothing to do with your net refund or net balance due. It has to do with your tax liability before taking into account what you may or may not have had withheld, paid as quarterly installments or applied from the previous year's overpayment. Other tax credits that reduce that liability, however, may impact your ability to use some or all of EV/Hybrid tax credit. I've used the $7,500 twice, but never had other credits, so I can't be more specific as to WHICH one(s) may have an impact.
