Computer cooling firm Allied Control estimates the total power consumption of the Bitcoin network at 250 to 500 Megawatts. Looking at the total hashrate, which is the number of calculations the network can perform per second, and applying a generous miner efficiency of 0.6 watts per gigahash, we can estimate our own back-of-the-envelope Bitcoin network constant power draw at just under 215 MW, although this figure is always in flux (it's important to note that many of the variables in my calculation are constantly changing slightly). That's around enough zap to power 173,000 average American households' daily electricity usage.
Bitcoin's power usage per transaction isn't remotely sustainable as a wholesale replacement for the conventional financial system
The bottom line? Price = energy. "The total revenue of the mining industry is Bitcoin price times BTC revenue in USD/day, independently of anything else; and the electricity consumption, also in USD/day, is some large fraction of that," concludes Stolfi.Green agrees: "Almost everything in Bitcoin is flexible, but that dynamic isn't. Miners always have the incentive to throw as many hashes [requiring power] at the job as the price dictates."Of course, it wouldn't be fair to knock Bitcoin's electricity consumption without comparing it to payment systems most people use today. Let's take VISA as an example.According to Network Computing, the VISA network can process more than 80 billion transactions per year or 2,537 transactions per second, using two mirrored data centers, each capable of running the entire network. The larger data center is currently pulling enough power for 25,000 households' daily electricity, so we'll double that to account for VISA's total draw. In 2013, VISA's investor reports say the company processed 58.5 billion transactions.
That makes Bitcoin about 5,033 times more energy intensive, per transaction, than VISA