If memory serves me correctly I believe Israel (or maybe it’s China) mandates that new construction install solar water heaters. (I’m not for mandates, but I do think solar water heaters should be given a lot more attention.) I know both countries have put a lot of effort into making those units more efficient. I think it’s one easy (and can be inexpensive) way that we in America could be saving a lot of energy (especially in the sunny regions) since hot water heaters are one of our main residential uses of electricity.
I think we should put solar panels on top of each of 12 new nuclear power plants when we build them!!!
Solar hot water is a very good application and pays back.
We could displace quite a bit of diesel fuel from it.