with a i5 you can mine with minerd ( a cpu miner ) at 35kH/s but it makes only sense with a brand new coin and a very low difficult
with E8600@4,33GHz (120w) ... i can mining at 4MH/s.
with GTX280 (430w) = 80MH/s
with USB block erupter (5w) = 333MH/s
with BFL miner (42w) = 12000MH/s
so ... you want mining for what ?
that it's the real question.
If you want help the network, ok.
If you want to found a block ... no luck, don't try.
a example:
a ATI R9 280 at 730kH/s at 400 Watt ( Power Cost 0,30$ / KWh if you pay less them get lucky ) mines DOGES
Time Frame DOGE Coins BTC (DOGE/BTC at 0.00000170) USD (BTC at $925.60) Power Cost (in USD) Pool Fees (in USD) Profit (in USD)
Daily 7256.93613933 0.01233679 $11.42 $2.88 $0.00 $8.54
Weekly 50798.55297531 0.08635754 $79.93 $20.16 $0.00 $59.77
Monthly 217708.08417991 0.37010374 $342.57 $86.40 $0.00 $256.17
Annually 2648781.69085556 4.50292887 $4,167.91 $1,051.20 $0.00 $3,116.71
thats only theory at the moment, in practice the difficult and the exchange rate is variable