Ok I just saw an ad on here for the vf100. It's not a boiler, it's a furnace. So I assume it provides heat on demand. Also it has no storage I believe. So what I would like to know is how it burns on and off but yet is still so efficient. My homemade gasifier that I made(shared in my previous post) was originally going to be a boiler, but after seeing the VF100, I'm toying with the idea of making it a furnace. But I can't load it every hour or two. I'm just wonder how they are controlled. Thanks for any insight.