It's probably not a good idea to wait with installing solar panels, because the solar energy tax credit decreased to 26% for systems installed in 2020 and to 22% for systems installed in 2021. And the tax credit expires starting in 2022 unless Congress renews it.
But I lose the EV credit if my tax burden is not high enough to fully utilize both within the same year? Since the EV credit should be $7500, it is not insubstantial, and I believe it would be greater than the 4% decrease in the solar credit (since the estimated system cost is around $37000 for my home).
Yes, that could happen. You might not be able to use both credits if your tax liability isn't big enough, since both credits are non-refundable and you cannot carry unused part of the credits toward future years. However, the solar tax credit might not be available at all starting next year, therefore to use part of that might be better than nothing. I would also recommend you to check your electric vehicle manufacture here:
Hi racingdragon -
In making your decision, I believe the 2nd comment from npierson1 is incorrect when she says "you can't carry unused credits forward to future years." That's true of the EV credit - but not the solar energy credit. See the instructions for IRS Form 5695 and see Line 16 of the form itself - where you compute the amount of the solar energy credit carried forward.
All things considered, too many tax credits isn't such a terrible problem to have. Do you have an IRS reference for being able to elect to take the EV credit before the solar energy credit - even when the solar energy credit is a carry forward from a prior year?