Here's the thing about efficiency

There is a totally obvious thing that we should probably see. People could easily store a large amount of energy as heat in water. If you haven't thought about it, then it probably doesn't make a great deal of sense: It would be good for just about everyone to have a substantial amount of fresh water from rain. This way you would have ample water for fire suppression. You could water your garden, or yard or children or whatever. Water is the best for holding heat, or cold as ice. That means better than anything else. You could catch enough cold in winter to cool your house in summer.
Then you have the possibility of using clean methane to generate your electric and saving the heat in your hot water reservoir which will then heat your house. with hot water heating In the future it will be more cyber controled so it might follow you around. The way we do it now, surely must be information controlled because we can do much better.
The same goes for car engines. If burning too much is a huge problem we would cut it way down if we tried. They are trying to sell an burn as much as possible.