"We need #4 THHN. 185 feet. And I’m going to need to cut a new trench to the panel."

But the calculator also showed him the why . He clicked "Show math."

"How do you know?"

It showed the resistance per thousand feet for #4 copper: 0.248 ohms.

He needed thicker cable. But how thick? Too thin, fire. Too thick, he’d waste a fortune on copper he didn’t need and couldn't fit through the conduit.

The rain hadn’t started yet, but Marco could feel it in his knees. He was crouched inside the crawlspace of the old Cannery Row building, a flashlight between his teeth, staring at a junction box that looked like a rat king of old wires.