tl;dr: Most people don't value Bitcoin as a payment mechanism, and even if they
were, most payments are not recorded on-chain. So calculating the energy cost of
a transaction is as impossible and nonsensical as it would be for gold.
It's true in a similar way that the lack of pirates is causing global
Yes, this is a valid estimation of Bitcoin mining's energy use divided by a
valid estimation of on-chain transactions, compared to a probably valid
estimation of household electricity use.
However, connecting these three figures in this way doesn't yield any insight
beyond shock and awe. That's because Bitcoin's primary value is not as a payment
network, so the number of on-chain transactions is not an interesting metric for
it. This can be seen easily: On one hand the number of onchain
has always been limited — and that limit has been pretty much hit constantly
since at least 2019. On the other hand, the value of Bitcoin, as well as the
estimated number of its users, has been rising over many orders of magnitude
since 2009. How can this be possible?
In recent years, long term store of value has become Bitcoin's main use case. That is, people use it more for storing their savings than for paying for goods and services.
Its current usage is thus more comparable to gold, which is also rarely used in transactions. I have never seen anybody calculate the energy cost of gold mining plus handling divided by the number of physical gold shipments. Probably because that's as misleading a number as the equivalent in Bitcoin.
Just as with gold, there are ways to make even small transactions quickly and cheaply with Bitcoin. Most real-world transactions use one of these off-chain methods. Probably the most popular today are custodial services like exchanges. Sending bitcoin from one customer to another on a service like this just requires changing two numbers in their database and is the equivalent of gold in a bank changing owners. It's hard to say how many such transactions there are, since there are many "bitcoin banks" and their numbers are proprietary, but it's safe to say they dwarf on-chain transactions by orders of magnitude.
Unlike gold, there are methods of transacting Bitcoin off-chain that require less trust in intermediaries, such as the Lightning Network or Blockstream's Liquid federation. With a growing demand in transactions, such alternatives are refined and gain popularity, without this being reflected in the above numbers. With the Lightning Network, it's even difficult to estimate how many transactions are being performed, since there is no central ledger recording them all.
But I have read that Visa transactions are much more economical!
That's because these are very different things. Visa transactions are just a few
companies changing a few numbers in their databases. It's basically just a fancy
way of signalling an intent to spend something. It's not final. There might not
be a real transfer of value happening at all (all the "money" is still debt in
the same bank, just on another account).
On the other hand, a Bitcoin onchain transaction is a real transfer of a bearer
instrument, comparable to a gold shipment from one central bank to another.
Those are also quite expensive, I imagine. It's total overkill if you want to
buy a coffee. For that, it might be enough to just update some numbers in a
(Bitcoin) bank. Or use the Lightning Network.
If you have a little time, Nic Carter has explained it much better than me.
If you have more questions regarding Bitcoin's carbon footprint, I recommend the FAQ at netpositive.money