I have a 13 year old furnace and an A/C unit that's gotta be 20 plus years old.

I'm thinking of replacing the ac with a mini split and keeping the furnace as back up for super cold days.

I forget. What is the low temp that they become inefficient?

We very seldom see temperatures that low. In fact its been a few years since its been that cold here.
I think we'll still have to use our pellet stove from time to time. This unit uses 1500 watts total at its max so that would figure out to a tad less that 3 dollars a day at the coldest it will work in. I'd say our medium temperature here is somewhere around 40 degrees so it should save us quiet a few bucks a season.
we pay 9 cents a KWH here

I seem to remember reading something about not being efficient below some number in the teens. Which would still be OK for me even in Chicago.

Let me know how it goes. I figure I can do most of the work myself and maybe find an HVAC person to do the purge etc.

My understanding is they come loaded with refrigerant??

It draws 1500 watts max so that indicates that it will be a much more efficient unit than what we're using which is very good or propane or electric our other two options

I figure it will take me a week to install it as I've got to remove our air conditioner from the the wall and patch it because where it is now is where I'll put the inside unit. I'll try to remember to let you know how it's working here in a couple three weeks.
The last thing I want to do is send anyone down the wrong path.
I have a friend who installed one last fall and he's heating the same amount of floor space as I, I don't think his house has as much insulation as we do. So far his electric bill has gone up 32 bucks a month from what it was last season and that was for the month of December which was the coldest month we've had that he's gotten a bill for. This last month I think has been somewhat colder than December was though. He was using 500 plus gallons of propane per winter and not keeping his house as warm as he is now. 68 on propane, 73 on the mini split.
I know another person who changed their central air unit to a heat pump and its cut their heating bill by a half. Where they live they have natural gas which is a lot cheaper to use that either propane or electric is.
Its hard to compare one winter to the next as the weather changes but last winter around here was real close to what we're seeing this winter.
Our pellet stove is pretty efficient and this winter we'll spend somewhere close to 500 bucks to heat with so if this unit saves us a couple hundred bucks or so a year it will have paid for itself by the time my wife retires. I'm already there on fixed income. I'll be 65 thursday of this week.

and I should have my heat pump thursday after noon, march 28
Hopefully I'll get in installed next week and I'll let you know what you asked me then.
One of my brothers is a HVAC man so I've got that covered.

Did you buy on-line?

haven't got an invoice yet to know what it cost to hook up but I'm thinking that its going to be somewhere between 150 and 200 bucks for installation.
won't know how well it works for another day or so as its like spring weather out today.

That's cheap for the install.

Was that just for the purge and hook up?

I'm thinking I can do the electrical, placement and wall unit mounting. I'll just need someone to do the purge etc. piece.

I put the electric box on the out side wall, I put the bracket for the inside unit to hang on and I also put the piping and electric for the inside unit, plus the drain hose through the wall. I let the installer hang the inside unit and connect the piping and drain hose and connect the electric cable between the two pieces.

It is a pretty simple install that you can do yourself except for pulling the vacuum to dry the lines. If you have a vacuum pump and gauges I suspect you can do that too. After the install the installer turned it on cool and set the thermostat at 62, I had the windows open as I forgot to shut down the pellet stove before they got here and it was nice and warm in here and knowing that most people don't care to work in a hot place I opened the house up for them. it got to 70 degrees outside today. Anyway it brought the house down to 66 degrees with the windows open in about 20 minutes then we closed the windows, outside by then it had dropped to 65 degrees and then set the unit to auto and let it warm the house back up. Set the thermostat at 72 and in about 20 maybe 30 minutes it had the house back up to 73 and holding it there. How quiet it is is the first thing we noticed.
Its going to take a bit to get how it operates down. Right now we just set it to auto and 72 and will let the unit take care of the rest.