Installed air-to-air mini-split heat pumps last summer. 3 indoor head units upstairs, but don't bother heating the lower level since nobody lives down there. They kept putting out heat last Saturday when the outdoor temp hit -17. They did, however, use a lot of kwh that day. I left my 25 year old oil burner and baseboard hydronic system in place as a backup, but I've not needed to run it yet this season. I fired it up last Friday and set the thermostat at 64 in case the mini-splits couldn't keep up, but they kept the indoor temp at 70 so the circulators never kicked on at all. Cost to install was about $12K including electrician. One 12K btu head unit and two 9K btu head units. A/C is a huge bonus, and the units are almost silent. I have a gasoline generator I can hook into my house panel which will run the oil burner and circulators in the event of a power failure. I got about $800 rebate from the state, and I think I'll be getting a nice federal rebate when I file my taxes this year. I'll probably be adding a solar system this summer to reduce cost of heating even more.