Bitcoin’s Exorbitant Energy Costs May Prove to Be Biggest Risk, by Sid Verma.

Even as bitcoin flirts with $8,000, the price required for mining to be marginally profitable stands at a jaw-dropping $300,000 to $1.5 million by 2022 based on current growth trends and electricity use, according to Christopher Chapman, an analyst at Citigroup Inc. …

“We don’t think that those levels of mining can be reached, and that governments will regulate/tax miners as a way of reducing the power consumption,” Chapman said in an email Thursday.

Mining costs go up by design as the number of bitcoins approach the design limit of 21 million:

Mining, combined with the peer-to-peer network, known as the blockchain, form the backbone of the virtual currency, facilitating transactions and maintaining the online ledger for coins in the system. Miners, in turn, are rewarded for taking part, under what is known as a proof-of-work system.

They have faced an uphill battle in procuring the virtual currency in recent years as the number of bitcoin awarded is reduced amid rising costs and breakneck competition, which has intensified amid the growing clout of virtual currencies on Wall Street. The pace of creation is limited, and no more than 21 million will ever be issued. ..

Those challenges have sparked calls for a shift to a proof-of-stake model, which would permit users to mine and validate transactions as a proportion of their underlying ownership of the digital currency. That would undercut the current system of rewarding miners with the most computing power, say proponents.