If your energy is less or maximum at 0.07 dollars/kilowatt then it is worth to mine bitcoin yourself, with a mining rig with multi graphic cards or with an antminer S9. This is only to be done if you are willing to wait a long time until bitcoin price goes up a lot and you make a lot of profit but it is not worthy if you want to run it for a short time and in fact is not recommended for this scenario. If you are in for short term better buy bitcoin directly and wait until the price of bitcoin goes up.
I've put your mistake in big, bold letters...
https://en.bitcoin.it/wiki/Non-specialized_hardware_comparisonThe best single GPU on that list hashes at 0.9 Gh/s with an extra power draw of ~400 Watt (extrapolated from the 2x Ati 6990 rig). Granted, this list hasn't been updated in a while, but it's not like the new GPU's are 50 times more efficient (actually, at the time of writing, the new GPU's would have to be 1000 times more efficient than the GPU's on this website just to break even... This is certainly not the case).
If we plug these values in coinwarz at current diff and btc price with a 7 cent/Kwu power price and a 1% pool fee:
https://www.coinwarz.com/calculators/bitcoin-mining-calculator/?h=0.9&p=400&pc=0.07&pf=1&d=1103400932964.29000000&r=12.50000000&er=3859.50010000&hc=0.00You net LOSS would be $0.67/day if you ran this setup.
Sure, if BTC prices rose to extreme heights, you might break even in the end, after holding your mined coins for decades. But if, instead, you bought BTC directly with the money you would have spent on your power bill, your profit would be much higher than when you mined at a loss and kept your btc untill the price was so high you were ROI'ing.
Proof of this statement:
1) you mine with 10 GPU's at 9Gh/s consuming 4Kw for one year...
power costs: ~$2500
Income: 0.00074863
BTCThe BTC price would have to go up to 3.34 million USD per BTC in order for you to break even. If, at the time one BTC costs 3.34 million USD/BTC, you sell your 0.00074863 BTC, you would have ROI'd (no profit, just broke even)
2) If you bought $2500 worth of BTC today, you would get 0.68 BTC
costs: ~$2500
Income: 0.68
BTCIf, just like in the first example, the BTC price would rise to 3.34 million USD/BTC, your 0.68 BTC would have a net worth of 2.3 million USD.
So, in conclusion, buying BTC and holding it would be about 900 times more profitable than mining with a GPU and waiting untill the mined BTC are worth enough to break even