How much oil was used previously for both hot water and heat? Is the goal to virtually eliminate the oil by burning wood in the Tarm? I assume this is the case, so we could come up with a close approximation of the wood needed by adding the 5 cords burned previously in the woodstove to whatever amount of heat was previously produced by oil, converted to cords of wood. Your comment about the bedrooms being cool with the woodstove reinforces my previous point. With the Tarm you will be heating the entire house to a higher temp. than you did before... The good news is this means you will be much more comfortable, have better control etc. etc. The bad news is this means more wood, notwithstanding the efficiency differences between the stove and the Tarm.