In Private Letter Ruling 201809003 the IRS ruled that a taxpayer who added a storage battery to an existing solar energy system for which a credit had been claimed in a prior year qualified for the solar device credit under IRC §25D(a)(1). But the IRS noted that there was an important factor in the facts the taxpayer provided that allowed for the credit.In Private Letter Ruling 201809003 the IRS ruled that a taxpayer who added a storage battery to an existing solar energy system for which a credit had been claimed in a prior year qualified for the solar device credit under IRC §25D(a)(1). But the IRS noted that there was an important factor in the facts the taxpayer provided that allowed for the credit.