Even if you have free electricity ROI is hard to reach if you spend money for miners
In 4 years with free electricity, one still may not make their money back? I'm personally not a miner, and I understand it's too late in the game for the general population to get involved... but that sounds ridiculous. With free electricity, OP still shouldn't expect to turn a profit?
Tell us more about your mining capacity, and your location.
The way i would do it right now is grab all the S3 for under 80$ i can. Grab all the S5 for under 250$ and mine them for the next year. Wait until the halving to see what happen. But these generate Heat and Noise. So free electricity is not the only concern.
Give us more information.
