The guidance on this issue is unsettled in the energy industry. While the federal tax code allows for a battery energy storage system to qualify for the ITC when paired with solar (provided it is charged 75% of the time from the solar asset), the IRS has previously only dealt with this question in Private Letter Rulings (PLRs). To date, the IRS has claimed that a storage asset could be added to an existing solar asset and be eligible to claim the ITC but only if it is done less than one year after the solar asset went into operation and is at least 75% charged by the solar asset. Consequently, it is best for any retrofit project to seek the guidance of a tax lawyer before proceeding to develop such a project.