[mcosta]

You pay electicity with fiat money.

[vntok]

Solar panels are a thing. Depending on the region you are setting them up in, a couple dozen panels and a battery could reliably power an ASIC 24/7.

Hydro, wind are other possibilities.

[CRConrad]

“You don't need to buy electricity, you can just build your own power plant!”

Sure. You can easily create your own conventional fiat currency too, you just need to set up your own nation.