For example, on Amazon right now I see a Bitmain AntMiner U1 USB miner. It costs $70 and they claim it uses 2 watts and is a recent chip.
Let's say it has a lifetime of three years. Three years of two watts is 26 kWh, which will cost about $2.60, which means that for this chip, the electricity is only 4% of the total mining cost.
Of course the rest of the computer uses power, I'm assuming that either the computer is being used for something else as well, or a large operation has a special chassis holding lots of these chips and not wasting power on much else. Anyone who's not so efficient won't be able to compete.
The fact that bitcoin's mining cost is becoming dominated by hardware rather than energy is a very positive development, in my opinion.
A lot of the emerging currencies are focusing on memory-constrained hashing algorithms. RAM has price/energy ratios similar to what I mentioned for ASICs, and is already in mass production and about as optimized as major industry is able to make it.
That unit does 1.6 Gigahash / second.
The bitcoin earned in a period of time will roughly follow that proportion.
I don't get this argument. Why do they have to be used for something else after "you're done with them"? You've made your profit with them (since if you aren't going to make a profit with them, you aren't going to buy them in the first place), so what else would you use them for?
The ASIC's serve a purpose: mining Bitcoin and maintaining the Bitcoin network. I don't get why there has to be "something else" they need to be useful for. Bitcoin is the point.
However, even if it were to change, there are several altcoins that use the same hashing algorithm (PeerCoin being the biggest), and/or someone will invent a new blockchain service to take advantage of the existing hardware. While I think there is great merit to ASIC-resistant hashing algorithms of ProtoShares/PrimeCoin/etc, that ASICs would ever become useless seems highly unlikely.
Unfortunately though, my guess is that it is very very tough to estimate due to the sheer variety of hardware that is being used.
I am sure that a large number of people are still mining with GPUs which consume more power/mhash than ASICs.
I came across someone last week who was mining with a CPU, I am confident he's not the only one.
Note I'm not trying to be argumentative. I'm actually genuinely curious. Even just order of magnitude. Folks in the media talk about the energy cost, but never with any attempt to quantify it.
So 13 million gigahash per second translates into at least 6.5 megawatts. But 2 is a pretty aggressive figure, it's probably easily above 10 megawatts.