Remember when bitcoin was killing the planet?

In my last column, I parked one objection to bitcoin for another day: the energy it consumes. That was mostly because it was an unfair argument to begin with. But let’s try to put it to bed.

The honest answer, five years after the outrage peaked, is that the world has moved the goalposts, thanks to AI. The electricity used to secure the bitcoin network is no longer the most interesting number in the room, next to the appetite of the machines now munching their way through gigawatt after gigawatt in the world’s data centres.

Cast your mind back. For a stretch around 2021, you could not read a tech publication without a headline scolding bitcoin for boiling the oceans, using more power than entire countries to run a speculative token. It made for arresting copy. It was also, even then, a strange place to plant the flag. When someone bothered to do the comparison, bitcoin did not come off worse than the banking sector it is accused of threatening.

A 2021 study by Galaxy Digital put the network at about 113TWh/year, against roughly 263TWh for the banking system and 240TWh for gold mining. Yes, really. Galaxy is a crypto firm with an obvious interest in that answer, so apply the same suspicion I am asking you to apply everywhere else. Nevertheless, the point survives: the branches, card networks, bullion vaults and armoured trucks of legacy finance are not free. They simply do not arrive with a running meter attached. Bitcoin does, which is precisely why it became a target. TechCentral columnist Rob Price argued as much in 2022 .

The bitcoin network today draws an estimated 138TWh/year, on the Cambridge Centre for Alternative Finance’s 2025 numbers , or roughly 0.5% of the world’s electricity, and that figure has barely moved in years.

Here is where this argument usually cheats, so let me not. The world’s data centres used about 415TWh in 2024, around 1.5% of global electricity – based on International Energy Agency numbers . But that 415TWh is every data centre on Earth: cloud storage, streaming, e-mail, corporate workloads, the lot. AI is only a slice of it, and until recently a modest one.

The IEA puts AI at roughly 5-15% of data centre power in recent years, which on 2024’s total works out at something like 20TWh to 60TWh. Our World in Data reckons AI had reached about 155TWh globally by 2025.

Measured like for like, AI has only just drawn level with bitcoin, and in 2024 bitcoin was comfortably the bigger user of the two. AI has not dwarfed bitcoin’s energy use – yet.

What it has done is more consequential. Bitcoin’s consumption is bounded, capped by what miners can profitably spend chasing a fixed reward, which is why it has barely moved in years. AI’s is not constrained. The IEA expects AI to take 35-50% of data centre electricity by 2030, somewhere between 330TWh and 470TWh on its own projection – two to three times bitcoin, with bitcoin’s line flat.

The sermon from the anti-bitcoin brigade did not stop because bitcoin got smaller. It stopped because attention shifted to AI data centres.

There is a second thing the comparison reveals, which the headlines of 2021 would have found unthinkable. Bitcoin is the cleaner of the two.