I'm looking at a 2800 sf home about 70 miles from me - it was built in 2002. It's listed as forced air heat & LP. So here in MI, if I have a 500 gallon tank, how long will that last in the winter? We typically have to start heating in October. Coldest months are Jan. & Feb. I am used to heating with natural gas, so I have no idea how many gallons we use - different unit of measure. This winter, we had a couple heating bills of $380.00 per month.