which are just sand with energy added (the solar generation returns its energy invested in about 3 months based on their used 15% conversion efficiency solar to electrical). The only reason we're not doing this now is because so far we haven't percieved that we need to. How much energy has to be expended in collecting and distributing energy from the sun? That is, what is the net energy? The sun's energy is not un-tapped; 100% of it is currently employed powering the earth's natural energy systems and its life. So the correct term might be "divert" instead of "tap". Consequently, my second question had two parts. given that other resources are needed to divert solar energy to our requirements, is there a practical cap on the rate of that diversion? Lastly, given that solar energy needs to be diverted from other uses, where are the comprehensive studies about the maximum safe rate of diversion (I've seen one or two very limited studies on specific projects)? If you are implying that a Dyson sphere is involved in solving mankinds energy problems, I would venture that such a solution might be viewed as a bit "down the road", particularly considering the sheer volume of fuels and resources still available for our use. As to your interest in net numbers, I think the basic calculations demonstrated for the sheer abundance of energy available tends to negate the value of the question. Mother Nature wastes 99.9999% of every watt of output in transmission