Bitcoins are produced through a process called mining where computers spend energy and computational resources to solve a difficult mathematical problems that verifies a recent block of Bitcoin transactions.
The miner who solves the math problem adds the block to the blockchain and receives newly minted Bitcoin. The difficulty of the math problem depends on how much computational power the network have in total. As the Bitcoin network attracts more miners, the mining difficulty increases, and usually, the amount of energy a mining rig consumes increases too.
The Bitcoin network currently consumes about 2.55 gigawatts (GW) of electricity per year; to put that into perspective, the entire country of Ireland has an average electricity consumption of 3.1 GW, and Austria has an average electricity consumption of 8.2 GW per year.