Is there a lien on my home?

No, there is no lien on the home. Instead, you give the lender a security interest on the solar system until the loan is paid off in full.  The lender will typically file a UCC-1 fixture filing with the county, as applicable, to create a lien on the solar system.  The UCC-1 filing will be removed once the solar loan has been paid in full.

What is the security interest on the system (ucc-1filing)?

As part of the loan agreement, the lender will file paperwork with the county that states that the lender has a security interest in the solar equipment. This security interest is known as a UCC-1 fixture filing. With this arrangement, there is no lien on your home or property, instead the solar system itself serves as the collateral for the loan.