There’s plenty of demand for Tesla Inc.’s Powerwall home-battery systems. The trick is finding installers that have them.

Only 12 per cent of U.S. companies that install solar panels and residential batteries carry the Powerwall, a study Tuesday from Boston-based EnergySage and the North American Board of Certified Energy Practitioners found. Meanwhile, about 55 per cent of customers shopping for home-storage systems want them, according to the 871 installers surveyed in the report.

“Installers have indicated their frustration that the most popular battery is not available,” said Vikram Aggarwal, chief executive officer of EnergySage, an Energy Department-backed company that collects pricing and data on the solar industry and runs a website allowing customers to solicit quotes from solar installers.

Tesla declined to comment. One reason independent installers who participated in the survey may have a hard time finding Powerwalls is that Tesla shifted its strategy last year to sell most of its systems through its website and stores rather than third-party channels.

Another reason is the company converted some production lines for home- and business-storage systems to produce vehicle batteries instead. “Otherwise we would have done quite a bit more in stationary storage,” Chief Executive Officer Elon Musk said in a call with analysts last month. Tesla plans to double its energy storage installations this year, to more than 2 gigawatt-hours.

“Customers want brands they recognize, from manufacturers who have produced their television, fridge or car,” Hugh Bromley, a New York-based analyst at BloombergNEF, said in an interview.