While Bitcoin is the shiny veneer of the operation, it’s actually a means to an end — giving Scrubgrass a reason to run more than the electric grid needs so it can continue to burn waste coal.

For the first 20 years, the plant ran nearly constantly. It had a power purchase agreement with the local utility, which meant there was a guaranteed demand and a guaranteed price for its output.

When that ended, in 2013, Scrubgrass struggled to navigate the competitive power market, where the price of power was falling in part because the Marcellus Shale was making natural gas a cheaper fuel for electricity than coal, let alone waste coal.

Plants — especially smaller ones like Scrubgrass that find themselves on the margin — often run only at peak times when the demand on the grid raises prices enough to make it worth their while.

Having a constant demand, like the attached data center, means Scrubgrass doesn’t need to shut down when prices for power fall. It also means that when the grid needs it, Scrubgrass can act like a battery — instantly switching its power to the grid.

(Andrew Rush/Post-Gazette)

“I think 10 years from now, people are going to say, ‘Bitcoin is the thing that power plants do to regulate the grid,” Mr. Campbell said.

He’s already thinking of ways to route the heat produced by the miners back into the power plant. (Last winter, Mr. Campbell heated his home with Bitcoin machines).

Meanwhile, the plant, although no spring chicken, feels like it’s still trying to figure out what it is — a place where people tinker and experiment. Mr. Shaffer, who spent most of his career at the plant, proudly proclaims that his colleagues aren’t “typical power plant people.” A former restaurant manager runs the data center.

Mr. Spence, not a typical anything except an entrepreneur whose ventures over the years ranged from natural gas services to a health magazine, hung the framed photo of Scrubgrass just inside the front door of his home.

“They should be building more plants like this, not less,” he said recently. “It’s not perfect. I acknowledge that to you. But it’s damn good.”

Anya Litvak: alitvak@post-gazette.com