I have an outdoor wood heating system and it works great. This unit heated the water that then ciculated in to the house and ran in to a heat exchanger that is in my propane forced air furnace. this allowed me to heat with wood and if needed i could still use the propane forced air system if i had a pump failure, took a winter trip, or just didn't feel like feeding it wood. The problem is i am getting old and i'm getting tired of cutting wood and feeding this unit all winter long. Since i have a fair amount of money invested in this system i would like to add an electric water heater/boiler to this system. I would most likely drain the wood heating unit and just circulate the electrically generated hot water through the existing heat exchanger in the forced air furnaces plenum. The heat from the wood boiler was hard to beat. it also heated the potable hot water heater with a unit called a "side arm" and It would be nice to somehow retain the side arm as the hot water heater is propane and propane cost big $$ these days. One of the things that bugged me about the outdoor wood heater was the circulating pump that ran 24/7 all winter long. I think if i can find a suitable water heating unit i can save a bunch of money. I have a 1800 sq/ft walk out rambler in Cambridge Mn. I went through a tank of propane a month (380 gal @ $2.00 gal = $765.00 a month or $4590.00 per heating season) or 11 cord of wood ($1000.00 per heating season) so the wood was a great savings and the house could be any temp we wanted all winter and it made great hot water for showering as well. So what is a good electric hot water heating system that will keep up with the winter here in Minnesota. this would need to circulate thru the heat exchanger when the forced air furnace calls for heat. Is the electric unit going to be close to the efficiency of the wood boiler? I'm envisioning the electric water heater to only run when the forced air furnace tells it to. Is there a unit that can heat the water and keep up with the demand? Any help i can get would be great. I am tired of chucking wood. Wood is a young mans method thats for sure.