I've read several posts in the past week (in the "Shutdown point" thread, etc.) where people quoted a mining cost of $1.XX. I have my doubts.
For one thing, the individuals seemed to use a complex mathematical formula, which seems very prone to error. I prefer to take last month's electric bill, subtract last years' amount due (for the same month), and divide that amount by 30 to get my daily cost. That seems a bit safer, no? It counts everything from CPU cost to PSU inefficiency, extra AC, fans, the whole nine yards.
Maybe if you keep your PCs in a garage and you live far enough north where it never goes above 60 during the day you could throttle down your onboard fans, turn off all exterior fans, and get below $2. But when you keep mining rigs in your house, and you keep the temp around 70 (=pleasant for human habitation), then Texans and Alaskans are in the same boat. I find that I still need a small desk fan pointed between the cards, on low at least, to keep the top card below 84 degrees. For me, anything over 82 is the red zone. I don't want to damage my cards (remember that when you see my cards up for sale in the Goods sub-forum!
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I have most of my fans (intake, exhaust) turned off now -- in Texas we finally got Fall. But I'm still using around 90 kWh a day for my 6 GH/s. That's $7.92 for the approx. 3.5 BTC a day I earn. That comes out to $2.26 a BTC. As I type, the current price for BTC is $2.22.
Yes, I'm not in the coolest part of the country, but some Fall weather came in yesterday and the high is 74 today with a low of 43. And while my electricity isn't the cheapest in the country, it's pretty decent at 8.8 cents.
But I'm not at the low end of efficiency, either, as my cards are all 58XX series. True, I have no more than 3 in a machine... but I am using 80+ bronze PSUs, AMD II (dual core) CPUs, 2 GB RAM sticks, and 1 machine runs off a USB drive.
If anything, I'd say my setup is pretty average.
Here's what I don't get:
Estimated 1386207 in 1292 blks
Network total 11.314 Thash/s
Blocks/hour 6.46 / 557 sAnd considering that a good chunk of the network is mining on Deepbit, BTCguild, and other NON-MERGED-MINING venues, they are only earning BTC. So how can so many people be earning money (or even breaking even) at the moment?
Remember, there are Mt. Gox fees when you sell the BTC and unless you want to buy Alpaca socks with your earnings, you have to pay a middleman 10% to turn them into gift cards, etc. (I guess you could Dwolla transfer, but then you leave a paper trail.) So we're getting darn close to "below cost" for many people.