Outside wood boilers suck!
I know because my father HAD one, and he was either putting wood in it, cutting wood up to put in it, or gathering wood for it. My Mother often said she was an Outside Wood Boiler Widow because he was never home! He was a slave to that thing. Eventually it burned his house to the ground as it malfunctioned, caught sawdust on fire, which caught the wood pile on fire, and then his siding on fire...
Everyone I know that has one, got it for the same reason; "because the wood is free" they say. Within a few years though, their appetite for wood is so demanding that all have resorted to buying their firewood. As is, I have two outside wood boiler customers that I keep in firewood. One burns 40 cord a year and the other burns 150 cords per year. The later, when it is really cold out, consumes over a cord per day and has a 5 foot by 5 foot door on it.
But if you want to see how inefficient they are, look at their burn efficiency if you want to get depressed. They are rated at 35%, which means you are getting 3.5 cords of heat from every 10 cords it consumes. I know my Father's consumed 20 cords per year, which meant he was only getting 7 cords worth of heat from it, and basically working his hiney off for the other 13 cords that was going to waste. No thank you, I got better things to do then work up wood that I will not get any heat out of!