Most of these mining calculators are way off.
For instance one said that difficulty would be 2,221,000,000,000 by Dec-2014. That's over 1100 times the current network. I did a quick estimate and if the current network were all antminers, it would be worth about $180 million. So 1100 x $180 million is about ~$200 billion. So do you really think $200 billion dollars worth of antminers will be added before December?
Mining always trends towards barely profitable.
I just checked the historical difficulty, and found that it has been growing exponentially (~10% at first, ~25% later on) every 2016 blocks for like a year. Of course, we shouldn't expect it to keep growing exponentially forever, but it is hard to tell when that trend will stop.
FYI: Difficulty was 6.7M 10 months ago, and will be around 2.6B in a few days.
Yes, and that exponential jump corresponds to a major leap in mining technology from GPUs to ASICs where ASICs are ~1000 times more efficient. I would only expect to see very modest improvements in ASIC tech moving forward. Knc, Bitfury, Cointerra, and Hashfast have all shown that ~1W per GH at the wall is about the best we're going to get from ASIC tech moving forward.
I expect ASICs to continue to get more efficient, but the incremental improvements will be much smaller. I think the difficulty will level out in ~3 months unless the price of BTC explodes again. If the price of BTC explodes again, all bets are off and much more money will flow into mining hardware.
This is real interesting and has me wondering about the future of distributed mining.
For the average person, dedicating a room and a circuit breaker in their home will be the most they could do without starting to look at server room options.
With this in mind, a 15A breaker can generally provide about 1440W of continuous power safely which currently translates to around 800GH/s of hashing power...and this is pushing it.
Assuming your right about the 1W per GH, the maximum hashing power that the average person will be capable of would be around 1.6TH/s which by my estimates will only be earning 1BTC/month by the end of June.
If this is true there will be a huge shift to centralized mining facilities this year sometime which really worries me.
I really don't see how Bitcoin can survive centralized mining.