SolarCity, SunRun and Sungevity have received subpoenas from the Treasury Department’s office of inspector general for financial records to justify more than $500 million in federal grants and tax credits the firms tapped for performing work. The probe seeks to determine whether the companies accurately reported the market value of their costs when applying for federal reimbursement, which was calculated at one-third of the costs…

But the prices some of these industry leaders charged for their work were sometimes far higher than the broader industry’s market rate, according to solar experts and details of the Treasury investigation released in company reports. While firms can install solar panels for roughly $5 per watt of energy and make a comfortable profit, some firms were charging as much as $7 and $8 per watt.