The Pulse
A Walmart store in Indio, California caught fire, and it started on the roof rather than inside.
The building took 3.1 million dollars in damage, and the merchandise burning inside it came to another six million.
It was not the only one. By the end of that year, seven Walmart roofs had burned.
And all seven of them carried solar arrays put up by the same supplier.
And when Walmart went to court, the thing it blamed was not the panels.
The arrangement behind all of this is common, and it is rarely noticed by anyone shopping below it.
A retailer leases its roof to an energy company, and that company installs the rooftop solar, owns it, runs it and maintains it.
In this case that company was Tesla, which had taken roof space at more than 240 Walmart locations.
So when fires broke out at seven of those stores inside a single year, the same supplier was standing under every one of them.
Walmart filed suit in August 2019, alleging gross negligence and a failure to follow ordinary industry practice.
The complaint asked for the arrays at every store to be switched off, and put the damages from that one store above eight million dollars.
Which is where the story stops being about solar power and starts being about plain workmanship.
The filing did not argue that photovoltaic panels are dangerous. It argued that this installation was done badly.
It named negligent and dangerous wire connection practices, and connectors that were not compatible with the cables they had been mated to.
It also pointed at the supplier’s own inspection records, which had already flagged areas for improvement and errors still to correct.
None of that is exotic. A cable, a plug and a maintenance schedule are the least glamorous parts of any energy project.
They are also, in this particular case, the parts that were on fire.
And there is a good reason a bad connector matters more up on a roof than it would in a wall socket downstairs.
A solar array produces direct current, and a direct current arc behaves differently from the alternating kind in a house.
Household current crosses zero a hundred and twenty times a second, and an arc goes out at every crossing.
Direct current never crosses zero, so once an arc strikes across a loose or corroded joint it can simply keep burning.
Worse, a panel cannot simply be switched off from below. As long as daylight lands on the glass, the array up there stays live.
Which is why modern codes require arc fault detection and rapid shutdown hardware, and why the joints get inspected rather than assumed.
Because the remedy asked for in the filing tells you how serious the retailer thought this had become.
Walmart did not just ask for money. It asked the court to have the arrays removed entirely from more than 240 of its buildings.
The complaint also went after the people doing the work, alleging that the installer routinely sent out inspectors who lacked basic solar training.
It claimed systems had not been properly grounded, and that panels carried a high number of defects that were visible to the naked eye.
Which is the detail in the whole filing that stings the most.
If a fault can be seen by someone standing on the roof, then the inspection regime is the failure rather than the technology, as the filing was reported at the time.
The same gap between the hardware and the upkeep decides the outcome at a solar site or an offshore project.
Neither company walked away from solar afterwards, which is the part that usually gets left out of the retelling.
Walmart and Tesla settled in November 2019, and the terms were never made public, as the trade press covered at the time.
Their joint statement said safety was a priority for both and that they looked forward to a safe re energization of the systems.
Which is corporate language for turning them back on, and that is what happened at both companies.
So the honest lesson from seven burned roofs is a good deal narrower, and more useful, than it first looks.
The technology on those roofs was ordinary and it stayed. What failed was installation and inspection, on a scale where one contractor’s habits repeat across hundreds of buildings.
And a homeowner reading this should take the same thing from it. Ask who inspects the joints, and how often, rather than whether to have the panels at all.

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