There is a concept of "energularity" similar to the technological singularity. Ray Kurzweil talks about exponential growth of solar power. I am sure electricity will continue to get cheaper to produce. It will always cost something but the cost can be spread out over many users. Sort of like water. I can take a water bottle and fill it up at a public drinking fountain for free. I didn't directly pay for the public drinking fountain, its installation, maintenance or even pumping the water from its source and filtering it. A small fraction of everyone's taxes went toward those costs. A bunch of people paid a few cents for water to be given out for free.