Deductions & credits

How do I claim credit for 2 energy efficient heat pumps I installed in 2020?

I understand there is a $300 credit per heat pump.

I installed 2.

When I enter the cost of 2 systems ($15,000) under Energy Efficient Building Property, TurboTax kicks out $300 total credit.

Is this correct?

Am I not eligible for 2X$300= $600 ?