American supermarket chain Walmart is suing Tesla over claims that solar panels supplied by Elon Musk's company keep setting its shops on fire.

The panels, which were installed and maintained by Tesla, caused fires in no fewer than seven Walmart stores across the US, according to a lawsuit (PDF) filed in a New York state court earlier this week.

An evidently upset Walmart bawled in its filings about the "utter incompetence or callousness, or both" of Tesla techies involved with the panels, with one fire allegedly happening after the solar panel system was "de-energised".

Not holding back from expressing their paymasters' feelings, Walmart's lawyers branded Tesla's solar power division as having "an ill-considered business model that required it to install solar panel systems haphazardly and as quickly as possible in order to turn a profit, and the contractors and subcontractors who performed the original installation work had not been properly hired, trained, and supervised."

It is alleged that the Walmart fires cost the supermarket firm millions of dollars in direct losses and in repair work to fix the damage.

Tesla acquired its solar panel division by buying out Solarcity for $2.6bn in 2016. Tesla, which has tried rather unsuccessfully to brand itself as a "vertically integrated sustainable energy company", hasn't done well with its solar energy venture. Reuters reported that solar panel installation rates plummeted 85 per cent since the buyout.

Walmart wants Tesla to pick up the cost of stripping out the 244 solar panel installations on its buildings around America.

Tesla has yet to comment on the case, nor has Elon Musk tweeted about it, other than mentioning a convenient relaunch of Tesla Solar three days ago.

We have asked Tesla to comment. ®