[plopilop]

A real, complete comparison is impossible as the two systems are fundamentally different and too complicated. What I like with that comparison is remains very simple. If you'd scale BTC to the amount of tx operated by VISA/MC, you'd need around 50% of the world electricity, which is clearly more than what Visa takes. Also it's a comparison of the fundamental part of the exchange, i.e. the authority checking for the authorization (visa or the miner).

If we incorporate the lightning network, then we must also take into account the electricity to run the servers for the intermediate exchanges etc. On the other hand, one could also lower the fiat electricity cost by factoring in the cash transactions.

TBH i'd be interested to see a reasonable estimation of the BTC+lightning emission costs per transaction, I'll admit I have no idea how much lightning brings the cost down.

[scottiebarnes]

> If you'd scale BTC to the amount of tx operated by VISA/MC, you'd need around 50% of the world electricity

Well, it doesn't make sense to scale the main chain in that sort of way, because you'd be looking at blocks the size of several terabytes in order to fit in global scale transactions. And so running a node would then require you to basically run a data center, which wouldn't make the system decentralized at all.

Electricity for mining is also not directly related to transaction throughput. Mining is the arbitrage of bitcoin price and electricity/mining hardware cost. The system technically does not need more electricity to secure the same amount of transactions. What happens is when bitcoin's price goes up, so does that arbitrage value, giving mining a profit incentive.

[plopilop]

> because you'd be looking at blocks the size of several terabytes in order to fit in global scale transactions.

My comparison would rely on running several bitcoin networks in parallel. Of course it does not make sense economically speaking, but it allows for a back of the envelope estimate.

> Electricity for mining is also not directly related to transaction throughput

This is true, but when you look at the C02 consumption (which was the topic of discussion when I first posted, before my OP decided to completely change subject), the mining cost is what you look for.

[scottiebarnes]

> My comparison would rely on running several bitcoin networks in parallel. Of course it does not make sense economically speaking, but it allows for a back of the envelope estimate.

Mmmm, I understand you're looking for a convenient way to mathematically equate the two on a per transaction basis for comparison's sake, but its just really difficult. For example, your several bitcoin networks in parallel doesn't really exist, because separate networks running in parallel are not interoperable (Bitcoin vs Litecoin). You lose the utility of network effects, etc.

Its like comparing energy costs of bicycles and ocean freighters, but no amount of bicycles could ever tow freight across an ocean.

[plopilop]

> You lose the utility of network effects, etc

Oh yes, you lose a lot of functionalities, but it's not the focus of the computation, simply to estimate, with the current technology, how much it compares to Visa in terms of electricity consumption. To be honest it would maybe make more sense to actually scale Visa down to bitcoin transaction rate, as we can assume more linearity there. The end result is the same though.

> Its like comparing energy costs of bicycles and ocean freighters, but no amount of bicycles could ever tow freight across an ocean.

Quite. However it seems to me its seems unavoidable to do so, since energy efficiency is a big topic these days. Also, while nobody pretends to be able to carry a load across oceans with a bike, it is usually advised to commute by bike rather than a freighter.