Now you guys got me all thinking. So let's do a few calculations. Assuming the following:
- We start off at today's difficulty of 3,054,628
- Conversion Rate of BTC/USD stays steady at 1 BTC = $12
- Power Usage is 1 Watt/GH (BFL's claim)
- Power Cost is .10 USD / Kilowatt Hour
- 1 Month = 30 days
10x Drop in Production per GH (5x Increase in Network Size/Difficulty, 2x Increase due to halving of Reward) - 'Effective Difficulty' Compared to Today: 30,546,280Jalepeno (4.5 GH|$149) Produces 4.5 BTC/month and uses 3.24 Kilowatt Hours.
(4.5 BTC * $12) - (3.2 kwh * .10) = $54 - $0.32 = $53.80 Profit
RoI: 2.76 Months
Little Single (30 GH|$649) Produces 30.03 BTC/Month, using 21.6 Kilowatt Hours
(30.03 BTC * $12) - (21.6 kwh * .10) = $360.36 - $2.16 = $358.20 Profit
RoI: 1.81 Months
Single SC (60 GH| $1299) Produces 60.06 BTC/Month using 43.2 Kilowatt Hours
(60.06 BTC * $12) - (43.2 kwh * .10) = $720.72 - $4.32 = $716.40 Profit
RoI: 1.81 Months
MiniRig (1500 GH|$29,899) Produces 1,501.49 BTC/Month using 1080 Kilowatt Hours
(1501.49 BTC * $12) - (1080 kwh * .10) = $18017.88 - $108 = $17,909.88 Profit
RoI: 1.66 Months
20x Drop in Production per GH (10x Increase in Network Size/Difficulty, 2x Increase due to halving of Reward) - 'Effective Difficulty' Compared to Today: 61,092,560Jalepeno (4.5 GH|$149) Produces 2.25 BTC/month and uses 3.24 Kilowatt Hours.
(2.25 BTC * $12) - (3.2 kwh * .10) = $27 - $0.32 = $26.68 Profit
RoI: 5.58 Months
Little Single (30 GH|$649) Produces 15.01 BTC/Month, using 21.6 Kilowatt Hours
(15.01 BTC * $12) - (21.6 kwh * .10) = $180.12 - $2.16 = $177.96 Profit
RoI: 3.64 Months
Single SC (60 GH| $1299) Produces 30.03 BTC/Month using 43.2 Kilowatt Hours
(30.03 BTC * $12) - (43.2 kwh * .10) = $360.36 - $4.32 = $356.04 Profit
RoI: 3.64 Months
MiniRig (1500 GH|$29,899) Produces 750.75 BTC/Month using 1080 Kilowatt Hours
(750.75 BTC * $12) - (1080 kwh * .10) = $9009 - $108 = $8,901 Profit
RoI: 3.36 Months
30x Drop in Production per GH (15x Increase in Network Size/Difficulty, 2x Increase due to halving of Reward) - 'Effective Difficulty' Compared to Today: 91,638,840Jalepeno (4.5 GH|$149) Produces 1.5 BTC/month and uses 3.24 Kilowatt Hours.
(2.25 BTC * $12) - (3.2 kwh * .10) = $18 - $0.32 = $17.68 Profit
RoI: 8.42 Months
Little Single (30 GH|$649) Produces 10.01 BTC/Month, using 21.6 Kilowatt Hours
(10.01 BTC * $12) - (21.6 kwh * .10) = $120.12 - $2.16 = $117.96 Profit
RoI: 5.50 Months
Single SC (60 GH| $1299) Produces 20.02 BTC/Month using 43.2 Kilowatt Hours
(20.02 BTC * $12) - (43.2 kwh * .10) = $240.24 - $4.32 = $235.92 Profit
RoI: 5.51 Months
MiniRig (1500 GH|$29,899) Produces 500.5 BTC/Month using 1080 Kilowatt Hours
(500.5 BTC * $12) - (1080 kwh * .10) = $6006 - $108 = $5,898 Profit
RoI: 5.07 Months
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If any of these 'effective' difficulties come true, mining will still be extremely profitable when you factor in power costs. But when you look at Return on Investment and trying to recoup your original cost of buying the units, things get a bit more iffy. You could even lose money in the long run. The network will not stand still and you'll be producing less per GH as time goes on. Also there's no way to know if the value of BTC against the USD will stay at $12, stagnate, drop or increase. I actually expect this at best, things will stagnate pricewise over the next 5-6 months as people will be selling their BTC as quickly as they can to try to recover their initial costs and there will be a lot more supply than demand.
Of course, all of this could be completely off base. BTC is a strange animal and the BTC/$ conversion could go way up or way down.