Mini splits are way to go. We have 4500 sq ft house. Built and insulated terribly. Have double oil tanks. Filled both every 6 weeks at cost of $2500 every frickin time. We went with solar farm with extra capacity on electric. Put in mini splits and now we use oil for backup only. Filled tanks once and will likely not do it again for years. Up front cost for splits and CSF was over 100k but now never an electric or oil bill ever. Still need to insulate better but oil heat sucks. Get rid of it!!