The analysts website Digiconomist estimates the annual energy consumption for bitcoins at around 32 terawatt hours (TWh).
The Bitcoin ranks in the same league as smaller states.
We are talking about 100-kilowatt hours (kWh) per transaction.
The reason for this is the SHA-256 Algorithms.
For comparison, 1 liter of oil ≈ 1m³ of gas ≈ 10 kWh
That means for a transaction here converted 10 liters of oil burned.
With ~ 300,000 Bitcoin transactions per day, we speak here of a volume of the equivalent of 3 million liters of oil per day.
Anyone who wants to watch the whole live can visit the following website:
https://www.blockchain.com/en/btc/unconfirmed-transactions
The size of the current blockchain is 213 GB (as of 04/2019)
Most of the energy for the stream still comes from fossil fuels.
The current annual consumption for Bitcoins was calculated by us based on the data from Digiconomist with 3,200,000,000 liters of oil.