You make a good point, and now I am trying to think of a way to add on some sort of boiler to an external burner to generate at least a bit of electricity along with heat for this upcoming winter.
Perhaps a bit more research into the matter is called for...
While it’s still in a sort of DIY geek stage, there are what appear to be reasonably priced thermoelectric generator units coming available, that can be placed on any source of heat such as a stove flue, with the temperature differential used to generate electricity. The most widely known commercial application of this to my knowledge would be those BioLite camp stoves with a USB port for charging cellphones and the like, but the thermoelectric units can be had individually for other uses. Here’s one source that popped up, no idea how reputable of a company they may be: