The rules may be changing with the possible passage of new legislation in congress. In theory it will extend the 30% solar investment tax credit for 10 years and give a tax credit on used battery electric vehicles. In both cases, making the credit refundable for those without enough tax liability looks like it didnt make it but in theory the solar ITC can carry forward to a future year while an EV credit does not. Things could get amended, or the bill could get shot down so in most cases it may be best to hold off on signing anything until it becomes law.