Also some folks get things at a very good price while others of us can't or don't have the resources. So that would be a silly bet. But if you can, then why haven't you done that? Or tell us how you can or did do it and WHEN you did it. I have a link to a page that says a guy put a homebuilt hydronic heater
in his travel trailer for $355. His most costly thing was an Hartell circulating pump for $155. These are 1991 prices. By reusing the rear heat exchanger from the bus along with the original coolant hoses, we can omit some things (like the fans, radiator) and we have an old RV water heater we can use. So that leaves me with locating a hot water circulating pump. Which will cost me more than the 1991 prices.
(I lost all my bookmarks so I don't know what one will cost). When we do our hydronic system, I WILL post the hows (along with pictures). Because this is something lots of folks will want to know about. Whether they choose to do it or not is up to them. And there will be some that improve upon what we do.
My big question is, if you know how to do it, then why haven't you posted HOW? Knowing how to run an AC air conditioner unit without a generator is something many converters would be interested in.