Underground Hot Water storage

[Countrypaul]

https://www.bbc.co.uk/news/business-65098792

[Mr Gus]

Quite a lot of interesting youtube videos on Swedens prepper families (bear in mind how they are located & have modern shelters in place for many thousands of citizens before anyone applies the term "prepper" as overzealous emergency contingency hillbilly type survivalist tropes.