Energy density is important in cars, but not at home. Additionally, the energy density of batteries increases by about 10% annually. Why would anyone want absolute self-sufficiency at all? If you store energy during the day and retrieve it at night, feed in some energy during the summer to make it available to the public, and buy some wind and hydropower in winter, I don’t even understand the problem to be solved. What remains is inefficiency or, in other words, unnecessary energy wastage.
