Correction: The electricity cost is directly related to mining rewards. As demand increases, so does price. So miners would purchase electricity at ever-higher

Correction: The electricity cost is directly related to mining rewards. As demand increases, so does price. So miners would purchase electricity at ever-higher marginal prices until an equilibrium is reached. Mining rewards come from the coinbase reward and txn fees. The coinbase rewards go down over time according to a schedule. Bitcoin is currently highly inflationary to create mining incentive, but we are rapidly approaching the 'long tail' part of coinbase rewards. Txn fee behavior is less predictable, and a source of significant conflict.