By reviewing the contract especially if the solar is financed. 9/10 times the contract itself will have verbiage regarding that state of the solar property and whether it’s considered “real property”. If the solar lien isn’t attached to the home, than it will not need to be subordinated.
Go to the solar company website. The website will have FAQs or more information regarding how the solar property will affect the purchase or refinancing of a home
Call the solar company directly and ask. When the contract is unclear and Title takes too long, I’ve called the solar company and verified directly with them whether they require subordination or not. My experience has been that they don’t want to deal with subordinations.