Normally, I would include the cost of hardware, but in this case the hardware is already necessary and sunk. It’s just a software addition, so the only incremental cost is the electric power.
If I was building dedicated miner hardware, then I’d calculate that as well.
Mostly I was trying to decide whether to leave generation on, or off, even in the event I had a real need for BTC. In this case, OFF was the obvious answer. It’s currently cheaper to buy BTC than generate them on this class of hardware. I’m curious to see if the market values adjust with the difficulty, or even the arrival of the power bill.
I suspect many of the big-number BTC miners are using someone else’s compute farm (work, school, etc) and externalizing the cost of the power.