How does the EV/plug tax credit work? Is it a refund or take off of money made or what is owed if anything. If just credit can it be carried over or just year purchased?

The EV credit is a use it or lose it situation and it can only be used to negate federal taxes only on your federal return.  It is not refundable nor can it be carried forward.   

Do you have a link that explains that?

assume your saying negate taxes owed so I should try to owe the fed gov the total amount to take advantage of it. A CPA tried saying it carries over until used up.