> We can all agree that IF the market cap gets this large, it will mean Bitcoin will have had a huge positive impact on society.

What, why?! Even if that were the case, it doesn't follow that the good it does outweighs using 1% of all energy.

I will explain.

Firstly, I think you are underestimating the societal impact that would have led a cryptocurrency to be worth $1 trillion. It would mean it has succeeded on a massive scale: foreign trade made more fluid thanks to Bitcoin's disregard of political borders, hundreds of millions of people using it to escape inflation/financial restrictions/etc (vs. today's few million users), millions of merchants accepting it (vs. today's 130 000 merchants). All Bitcoin would have to accomplish to justify using 0.X% of the world's energy is to increase the world GDP by 0.X%.

Secondly, 0.74% is an upper bound. It assumes power costs of $0.01 per kWh (read section 2 at http://blog.zorinaq.com/?e=82) when actually the average power cost worldwide is 10x higher ($0.10/kWh). Maybe it will be 0.3% of the total energy. Maybe 0.1%. How low is low enough that you would consider it worthwhile?

There is no level of hash calculations that is acceptable.

It is crazy to have a currency that requires this dumb make-work of hashing which results in CO2 emissions. We live in a world of dangerous climate change and Bitcoin users want us to expel CO2 into the atmosphere with every currency transaction. That is dumb and not sustainable.

I actually address this point in my post: "Many/most miners use hydroelectric power because competition compels them to use cheap renewable energy instead of other polluting power sources such as coal power plants" examples:

BitFury: https://www.businesswire.com/news/home/20151211005837/en/Bit...

KnC: http://thenodepole.com/2015/06/04/kncminer-to-build-new-20mw...

Therefore your worry about CO₂ emissions is misplaced.

> There is no level of hash calculations that is acceptable.

Well that's just unreasonable. Do you have any earthly idea how much CO2 the current banking system expends?

Question: does the model account for general increase in energy use, within the timespan of (and, possibly, also as a consequence of) Bitcoin growing to reach that market cap, or is 0.74% just the absolute amount of energy as a cut of today's total usage?

If the latter, 0.74% seems less alarming, as it would surely be less when growth is accounted for, especially considering that some of this growth would likely (hypothetically) be driven by an increase in both production and consumption as a direct consequence of the use of Bitcoin, with all the benefits that brings.

But either way, it does still seem moderately alarming, albeit as a kneejerk reaction to the figure without much critical analysis. It's a very interesting economic question as to whether investing this order of energy consumption into Bitcoin would be worth it, both for individuals and for society(ies). I expect many an economics PhD will be minted on this very topic!

It's the latter (0.74% of today's total usage, therefore 0.37% if the world's energy usage doubles).

That's the answer I was hoping for :-) Thanks!

Additionally, can only improve with increasing processor efficiencies over time too (unless this is also predicted for in the model) - though saying that increasing processing power is accounted for in Bitcoin itself, with the work getting progressively harder, so this may be moot

1 trillion is the current GDP of Australia, a modest szed industrial nation. 1% of energy consumption for just that much currency is not an all worth it.

Australia consumes 5831 petajoules [1] or 1620 terawatt-hours yearly. In my model miners would consume a comparable amount (actually less): 800 terawatt-hours. Therefore Bitcoin and the Australian economy extract comparable economic value from energy.

IOW if you think Bitcoin is not worth it, then Australia is not worth it :) Thanks for this interesting comparison!

[1] http://www.industry.gov.au/Office-of-the-Chief-Economist/Pub...

Australia keeps 25 million people alive in a first-world lifestyle. Bitcoin keeps computers warm.

No, Bitcoin creates more than just heat: it created thousands of jobs (see section "Bitcoin already benefits the economy" in http://blog.zorinaq.com/?e=82).