Chattanooga’s municipal utility, EPB, had installed a Tesla Megapack battery system on this lonely stretch of the distribution grid back in June. If anything knocked out the line, residents would have 2.5 megawatts/​10 megawatt-hours of storage capacity at their disposal while crews fixed the problem.

In this case, utility workers unexpectedly needed to de-energize the line to finish making repairs. EPB was able to switch the neighborhood over to battery power for about half an hour until the job was done. Without the battery, EPB would have had to tell its customers it was cutting off their power on purpose.

“This was the first time we used it in an outage situation,” said Ryan Keel, president of the energy and communications business unit at EPB. ​“In the future, it’ll be even more unplanned. It’ll be a response to a tree falling through the line or a car hitting a pole or something.”