my partner and I installed a heat pump, and each paid half. His turbo tax return gave a $1000 credit. I was credited $608. What would explain the inconsistency?

The difference in the tax credits you and your partner received could be due to several factors:

1. Tax Liability: The energy-efficient home improvement credit is non-refundable, meaning it can only reduce your tax liability to zero. If your tax liability was lower than your partner's, you might not have been able to claim the full credit. This is normally the biggest reason.
2. Income Levels: If your incomes differ, it could affect how much of the credit you can claim. Higher income might allow for a larger credit if the tax liability is higher. 
3. Allocation of Costs: The IRS might require you to allocate the credit based on how the costs were shared. If there was any discrepancy in how expenses were reported, it could lead to different credit amounts.