Our heat pump has been sounding strange for about a week or so. Our AC/Heat guy came to look at it earlier this week. He said the compressor in the heat pump is not working anymore. He explained that the anti-freeze in the furnace(attic unit) needs to match the new heat pump's anti-freeze. So, we're looking at purchasing a new heat pump/furnace combo for our home. Our home is approx. 1200 square feet. What brand/kind of heat pump/furnace have you found to be the most efficient monthly yet reasonably priced to buy?