My dad is a retired heat and power engineer up in Maine (20something years at a paper mill). We probably spent half of Christmas talking about his new minisplit. He has been tracking his electricity bill and heating oil bills in spreadsheets for years. He still has the old oil boiler in place for emergencies, but as far as I know he hasn't had to use it yet this year. He said he wanted more data before he made a definitive statement about the savings, but initial results seemed pretty promising even in the cold spells we've had