I wonder if people realise how much energy their computer consumes
The energy consumed by your computer is a function of the work being done the computer. If your computer is doing a CPU intensive task such as manipulating large amounts of data, then effectively your computer will be consume an enormous amount of energy, but if you computer is sitting idle it isn't really consuming that much electricity, probably 100watts. I'm tempted to equate that to a light bulb, but now the age of LED bulbs, it would be the equivalent of about 10 light bulbs. Your screens are probably consuming the most energy. Turn those off when your not in front of them.
In the case of Bitcoin mining, the task of hashing is extremely CPU intensive, to the point where nearly all of the energy spent, is used on cooling the CPUs or GPUs.
I will just point out that consuming electricity by producing goods (or I guess Bitcoin), when the demand for electricity is low, in cases where the production of electricity cannot be stopped, is likely a better use than simply letting the electricity or source or go to waste.
In a prior life I worked in the Aluminium industry, during that time there was a boom of Aluminium plant construction the Middle-East. The reason was that these oil producing countries where extracting a large amount of natural gas as a by product of crude extraction. Natural gas is land locked, as it can't be easily transported by sea. They had all this gas but nothing they could do with it. So they produced power plants, and now they had electricity but not enough consumer for the amount produced. So they decided to produce aluminium, as it's main ingredient in terms of cost is electricity, they could then ship and thus sell the aluminium. The world didn't need more aluminium smelters, but had they not produced aluminium the natural gas would likely have been burned of into the atmosphere. So the end result was that it caused a drop in aluminium price that in turn forced older less efficient plants to close which in turn meant less pollution and likely less C02 production (probably only a marginal drop).
Now the mining of Bitcoin doesn't produce any CO2 or pollution, while the smelting of aluminium does. (Note that both these activities require the production of electricity which does produce CO2 in most cases [obviously not in the case when renewables are used], so CO2 production from electricity in this case is a sunk cost [ie can be ignored]). I wouldn't be surprised if these countries have reduced the amount aluminium produced, in favor of using the electricity to mine Bitcoin thus reducing the production of CO2 and causing the price of aluminium to climb (I haven't checked the aluminium price so this is speculation not fact).
