The instructions for Form 5695, Residential Energy Credit, say:
- Line 22a: Don't enter more than $300 (this would be for the high efficiency A/C unit).
- Line 22b: Don't enter more than $150 (this would be for the furnace).
While these numbers are tiny relative to what you spent, that's what IRS regulations allow.
If you enter the information in TurboTax, you can enter the full amount you spent. TurboTax will be able to enter the correct credit, based upon your answers.