[steve86]

What about indoor propane heaters that you attach to a regular propane tank?

if you're talking about freestanding ventless propane heaters, those have been illegal in CA for a long time. I used to sell them; couldn't ship to the mothership state.

[bill1952]

That the one. I used them a bit in my hunting cabin.
Very nice item.

There are millions of homes heated by propane; most of them converted from oil for one reason or another.