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I plan to hash at around 250-550 gH/s, would it be profitable to mine solo, or would I make more money joining a pool? Are there any unexpected occurrences that I should look out for when mining?

Murch
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OrangeEnigma
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    Finding a block might be considered an "unexpected occurrence" when solo mining :) – Greg Hewgill Jan 07 '14 at 19:00
  • you should also run with GBT over getwork to give yourself a better chance at success – Joe White Jan 07 '14 at 20:00
  • If you do go pool mining, go to the smaller pools, the largest and growing majority pools are awful to bitcoin. Ghash.io has done some trickery with their tremendous hash rate. http://www.reddit.com/r/Bitcoin/comments/1qqmr4/ghashiocexio_and_doublespending_against_betcoin/ – John T Jan 08 '14 at 00:03

2 Answers2

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As @jtorba pointed out, your chance of finding a block is your_hashrate/total_hashrate, with total_hashrate being currently ~1.2e7 GHash/s. Average time to find a block is 10 minutes (actually somewhat lower, since the difficulty is increasing).

So, today your mean time for finding a block is between 5 and 11 months (for 550 and 250 GHash/s respectively).

However, there are other factors:

The distribution of probable times is pretty wide, so it's quite possible to get your first block after several months or even years.

Current trend is that total hashrate triples every 2 month. So, your chance of finding a block would be steadily and rapidly decreasing.

Short verdict: solo minig 500GHash/s is not enough to provide one with reliable mining income. It's not completely out of question if you wish to take risks.

Update: the probability to mine specific amount of blocks during this year when solo-mining with 550 GHash/s. Assuming exponential network growth.

Hashrate growth per 2 weeks | 0 blocks | 1 block | 2 blocks | 3 blocks | 4+ blocks 
----------------------------------------------------------------------------------
                  0%        |    9%    |   22%   |   26%    |   20%    |   23%    
                  5%        |   25%    |   35%   |   24%    |   11%    |    5%    
                 10%        |   39%    |   37%   |   17%    |    5%    |    2%    
                 20%        |   58%    |   32%   |    9%    |    1%    |    0%

Source code

Community
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aland
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You will make the same amount of money regardless either way, you may lose money on mining pool fees. Your change of getting the 25 btc reward is 

Probability per ~10 mins = hash rate/network hash rate

So 250/13000000 means 0.00001923076 chance of getting a block every 10 mins, you will be getting a block. To have 100% probability of getting the 25 BTC reward it will take 520000 mins (~1 year). In summary you have 100% chance to get the 25 BTC reward in a year with 250 gh/s.

With solo mining you split the profit of 1 miner finding a block to how much work you put in, but if the pool has a larger hash rate, the income is instant, comparing both methods you'd get the same amount no matter what, only downside is fees and the steadiness of income

These are estimates, difficulty and hash rate change drastically monthly, and 10 minute block time is the optimal time, not fact.

John T
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    36 days is average payout period. The probability of generating a block after 36 days in this case is around 70%. – aland Jan 07 '14 at 19:58
  • I think the second word should be "pool" in your last sentence... – Scrybe Jan 07 '14 at 21:37
  • Your math is wrong... 250/13000000 is 0.00001923076. What would the numbers look like if this correction is made? – OrangeEnigma Jan 08 '14 at 00:17
  • The number after the 250/1.3e7 is a percentage and multiplied by 100. @aland also is more correct that 36 days will get you only 70% chance at getting a block, my estimates exclude things like difficulty increasing exponentially. – John T Jan 08 '14 at 00:34
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    10 minutes / 0.001923076% = 520,000 minutes (which is 1 year), not 36 days as you wrote. – Meni Rosenfeld Jan 08 '14 at 07:58
  • My bad I see it now, and changed it so no one gets the wrong idea. – John T Jan 08 '14 at 08:06