You claim the full amount on 5695 and any unused credit is carried forward.

Dusty

"I was aware that solar pannel credits can only be claimed for the year that they were bought,"

It's an asset, so it falls under the asset rules of "in service" and "complete." Not over years and years for the same system.

If your client was told this by the sales person, then...Duh.

I love when client tells me the salesman said…. I tell them to have the salesman do their tax return…. Just read the instructions, you’ll do it correctly 

edit:   I installed the first solar panels in 1985. The salesman told me that it was renewable energy as long as the sun kept circling,  and not only was the energy renewable but so was the tax credit… so after an initial investment of only  $8650 …the tax credit has amounted to 73,432. 

This is why you are the preparer and he is the client. And always remember, sales staff will say anything to make the sale. Thats why they are salesmen and you are the preparer. Always go with your research and prior knowledge.

"so after an initial investment of only $8650 …the tax credit has amounted to 73,432."

Well, sure, but that was back when a dollar was worth a dollar.