The energy credit is only for your primary residence. So if the property was not your primary residence in 2019, you don't get any energy credits.
A Heat Pump falls under "all other energy improvements" and only gets you a $300 tax credit at the most. (could be less.)
If you don't have a tax liability before the credit, then you don't get the credit for 2019. It's carried over to the next year. So if your tax liability is zero before the credit, you can't use the credit that year because it's a non-refundable tax credit. However, you still "claim" the credit anyway. If you don't "claim" the credit on your 2019 tax return, then you can't carry it over to your 2020 tax return.