Air source heat pumps are about as costly to operate as natural gas in mild climates (where it's generally above freezing most of the time). If you do dig up yo

Air source heat pumps are about as costly to operate as natural gas in mild climates (where it's generally above freezing most of the time). If you do dig up your yard and lay underground pipe, that heat pump system will cost a fraction of natural gas to operate, even in Minnesota. And that's with natural gas prices at historic lows. Heat pumps are amazing.