For me equilibrium is about a month away. Do I plan to sell my cards, with that much raw computing power I can think of a few other projects to use them for in small bursts, not 24/7 like they have been. Maybe even play a few games, without worrying about the drop in hash rate.
Here is the guts of a post I was going to make when I noticed this thread and instead of posting a new thread with a very confusing title of "Sky rocket or go Magma diving ?" I decided to add to this thread ..... they are both ultimately about your own personal equilibrium day.
Sorry for the poor beginning, I always seem to start my posts at the middle and work my way towards the beginning and finally get to the end.
Cost of Electricity per Kilowatt hour unit for me $0.25 (fixed)
Power used by my rig per day (about 220W x 3 + misc) circa 750Watts (24*0.750*0.25) = $4.50 (fixed, unless I add more hardware)
Hashed by rig per day on average 1300MH/sec @ current difficulty of 1888786.70535 is 0.692 BTC.
Assuming that 1 BTC is currently worth about $10 this would be $6.92 mined per day. Great news for me, I am printing money, at a profit using the current exchange rate.
If I assume that the value will increase in the future, I could print at a loss today for a possible profit tomorrow.
Or I could assume that BTC is a bad techo/nerd/geek/investment fad and the value will suddenly drop through the floor, and that I am printing money for a loss today and will be hit by an even larger loss tomorrow.
But I am an optimist and am reminded of that old saying "Always buy land, there ain't any more of it coming along any day soon", that is of course unless you live in Hawaii
But if you bought land 100 years ago, there is one thing for sure and that is that it will have appreciated in value. And if I bought land today, in 100 years time it will also have appreciate in value. In between there are ups and downs but overall the value it is up. I think of BTC in the same way as minerals, there is a limited fixed supply. There are ways to get more minerals, by bring them back to earth from space, but the extra mass would slowly spiral our planet into the Sun.
So anyhow back to the task at hand lets work backwards. i.e. At what difficulty will the cost of electricity for me match the BTC being printed per day (at given exchange rates) ?
I have one constant the cost of electricity and two variables: the BTC generated per day on average and the exchange rate of BTC to dollars.
So to balance both sides of an equation I need to reduce the BTC generated per day to match my electricity costs.
$4.50/$10.00 would be 0.45 BTC per day to be operating at no loss and no profit. Or one 50BTC block found on average once every (50BTC/0.45BTC) 111.111111 days (111 days, 2 hours and 40 minutes)
Now here comes the flaw in trying to work out the magic difficulty, this duration of 111.111 days is larger than 14 days, which is the target duration of each new difficulty level (probably closer to 12 or 13 days in reality).
There is also a flaw that the future exchange rate all the way during the total 111.111 days will be constant and at today's assumed exchange rate of $10.00
Even with these two major flaws in the calculation both of which are unpredictable (BTC exchange rate and future difficulty growth[reduction] rate). Is having a flawed number better than having no number ? I would like to see a bad approximation rather than nothing.
The maths is trivial - see https://en.bitcoin.it/wiki/Difficulty#How_soon_might_I_expect_to_generate_a_block.3F
I'm just flipping the formula to get a difficulty instead of an average time for a new block.
difficulty = ( average duration for a block in seconds x hashrate in hashes per second) / 2^32 = ( 9,600,000 x 1,300,000,000 ) / 4,294,967,296 = 2,905,726.433
In my case a difficulty of 2905726.433 at a hash rate of 1.3Ghash/sec would yield one 50BTC block (ignoring block fees) found on average every 111 days, 2 hours and 40 minutes or 0.45BTC per day over 111.111 days (or a 54% increase from the current difficulty). This is as I mentioned assuming a constant exchange rate of $10 and a constant difficulty for 111.111 days of the 2905726.433 difficulty. 111.111 days divided by 14 days is 7.9, so the difficulty should have changed at least eight times during this period. But there is no way to know if the future difficulty will increase or decrease in the short term. In the long term it should increase, with increasingly more efferent future hardware.
Anyhow there is a decision that I will need to make, circa a month from now. Nothing is set in stone, the BTC exchange rate could sky rocket, or go magma diving. And the difficulty rate could increase (or decrease) more rapidly than expected. There should be enough information above to help you workout your own approximation to your own personal equilibrium day.
EDIT: Actually in about a months time it will be getting close to winter where I live, so maybe I will continue to mine for subsided heating. *evil grin* Maybe next spring/summer you will see a drop off in mining, but I think that every winter there will be an increase. Why generate heat without doing something useful to make the heat. There is an interesting idea, electric BTC radiators. Increase the hash rate to increase the temperature, and throttle the sharerate to lower the temperature. Maybe pulse it 5 minutes generating then allow it 5 minutes of idle, and adjust the on/off ratio to adjust the average room temperature. It would definitely be an idea that would get media attention. Although I don't know if it would be in a good way, or a bad way.
Anyhow here is a simple table, everyone loves tables, well except those who love graphs, bloody hedonists.
$/BTC cost of used electricity per hour (US cents)
5 6 7 8 9 10 11 12 15 20 22.5 25 30 40
1 The past The past The past The past The past The past The past The past The past The past The past The past The past The past
5 5448237 4540197 3891597 3405148 3026798 2724118 2476471 2270098 The past The past The past The past The past The past
7.5 8172355 6810296 5837396 5107722 4540197 4086177 3714707 3405148 2724118 2043088 The past The past The past The past
10 10896474 9080395 7783195 6810296 6053596 5448237 4952942 4540197 3632158 2724118 2421438 2179294 The past The past
12.5 13620592 11350493 9728994 8512870 7566995 6810296 6191178 5675246 4540197 3405148 3026798 2724118 2270098 The past
15 16344711 13620592 11674793 10215444 9080395 8172355 7429414 6810296 5448237 4086177 3632158 3268942 2724118 2043088
17.5 19068829 15890691 13620592 11918018 10593794 9534414 8667649 7945345 6356276 4767207 4237517 3813765 3178138 2383603
20 21792948 18160790 15566391 13620592 12107193 10896474 9905885 9080395 7264316 5448237 4842877 4358589 3632158 2724118
25 27241185 22700987 19457989 17025740 15133991 13620592 12382356 11350493 9080395 6810296 6053596 5448237 4540197 3405148
30 32689422 27241185 23349587 20430888 18160790 16344711 14858828 13620592 10896474 8172355 7264316 6537884 5448237 4086177
35 38137659 31781382 27241185 23836037 21187588 19068829 17335299 15890691 12712553 9534414 8475035 7627531 6356276 4767207
40 43585896 36321580 31132783 27241185 24214386 21792948 19811771 18160790 14528632 10896474 9685754 8717179 7264316 5448237
45 49034133 40861777 35024381 30646333 27241185 24517066 22288242 20430888 16344711 12258533 10896474 9806826 8172355 6129266
50 54482370 45401975 38915979 34051481 30267983 27241185 24764713 22700987 18160790 13620592 12107193 10896474 9080395 6810296
75 81723555 68102963 58373968 51077222 45401975 40861777 37147070 34051481 27241185 20430888 18160790 16344711 13620592 10215444
The top row is cost in US cents per KWhour of electricity and the first column is the BTC to US dollar exchange rate.
You are either ON the table or OFF the table. This is because "average duration for a block in seconds x hashrate in hashes per second" is a constant for everyone mining. So if you are mining less than the required number of BTC's a day to break even you can not be on the table above. So in my case I am mining 0.69 BTC per day (1.3Ghash/sec) and my electricity cost is 0.45 BTC per day. If I was CPU mining at 10MHash/second generating 0.01 BTC a day with the same power cost of 0.45 BTC per day (or anything greater than 0.01), even though I could read values from the above table, I would be asleep probably in deep space and would definitely not be ON the above table. My current exchange rate ($10 per BTC) and current cost (18.75 cents per hour) of electricity would be there and point to a cell with the difficulty equilibrium answer if I was mining sensibly.
So My rig uses 750 watts per hour or 0.75 KW hours at 25 cents per KW hour unit. Thats 18.75 cents (0.75*25) , the 20 cent column is the closest to my true value and at a current exchange rate of $10 would give the approximate value of 2724118 for 20 cents but if I adjust this (20/18.75*2724118 = 2,905,725.867) I get the same value as above, or as close as makes no difference: 2,905,725.867 instead of 2,905,726.433