SMK, the problem with hot plate is that too much heat is bypassing the job, as Mex put it. The heat dissipates from the plate, and from the walls of the pot. Propane is worse yet, a lot of heat goes straight into your living space, and it burns oxygen in the room. Electric boilers, kettles, coffee makers etc are better insulated, there is less loss of heat.
It's not just about saving the planet - we are already doomed. But if you are, like Mex for example, have to cook in a space where it's hot all day long, then the very thought of propane stove or hotplate is unbearable. Permanent campers in Mexico have an outside kitchen of some kind on the shady side of the rig or under palapa. Like a 2-burner stove on flimsy old table.