Tesla may be best known for its electric vehicles, but it also offers other electric power products, like solar roof panels and the infrastructure to go with them. Now one of its biggest customers – the largest retailer in America – is suing Elon Musk's company after several of its solar roof installations have caught fire.

Automotive News reports on a breach-of-contract lawsuit filed by Walmart in New York, claiming that Tesla has "engaged in widespread, systemic negligence and had failed to abide by prudent industry practices in installing, operating and maintaining its solar systems."

In its drive to draw 35 percent of its electricity from renewable resources by 2020, Walmart has reportedly either leased or licensed roof space atop over 240 of its stores for the installation of Tesla's solar power arrays. Tesla bought the operation from SolarCity in 2016 and has made it an integral part of its business.

Walmart claims that seven of those solar power systems had caught fire unexpectedly through this past November, forcing it to disconnect all the rest out of concern for its customers' and employees' safety and wellbeing.

In addition to installing the solar panels, Walmart has also reportedly ordered a pilot fleet of 15 Tesla Semi electric big-rig trucks. That's far fewer than the 125 ordered by UPS, the 100 ordered by PepsiCo, or even the 40 ordered by Anheuser-Busch. But Walmart is not working exclusively with Musk and company. It's also developing self-driving delivery vehicles with Ford, and has been installing charging stations with Volkswagen's Electrify America initiative. It may be too early to tell how this latest lawsuit might affect Walmart's overall relationship with Tesla, and what that might mean for its plans to deploy the electric Semi trucks... but it doesn't bode well.