Situation:

My small, home-based business occupies about 700 square feet of an outbuilding on my property. That space consists of a front office that is around 150 square feet, a back storage room that is around 100 square feet, and a central shop that comprises the rest. There is a small window A/C unit installed in the wall of the office portion and there are electric baseboard heaters in the shop and office. The window A/C unit appears to be failing and was never really useful at cooling anything but the office space. The baseboard heaters work fine but they're expensive to run. The shop can get uninhabitably hot in the summers and heating the office and shop areas in the winter can be very expensive. The result is that the space doesn't really get used.

With the air conditioner possibly failing, I am exploring my options and am curious about forum experience with ductless mini-splits. I would need/like to heat and cool the shop and office areas. I am assuming that will demand a two room installation to be effective as they are divided by a wall and steel door.

Does anybody have any relevant experience? I'm interested in rough costs both initial and operating, brand recommendations, etc. I've seen a lot of DIY information on these systems, but I would lean towards biting the bullet and having one installed by an HVAC company.

I had a mini-split heat pump installed in my home last August:
- 3-ton Mitsuibishi- 1200 SF
- single outdoor unit
- 4 indoor heads:
- 12k btu/hr in both living room and family room basement
- 9k btu/hr in master bedroom
- 6k btu/hr in 2nd bedroom
- $20k installed

I flipped coin between Fujitsu & Mitsubishi - rated 1st/2nd depending on reviews and features.

Need more time on op cost...windows AC units prior so no history. Pellet stove for primary heat but the heat pump was a charm for the tweeter months.

Eastern PA here so don't get the deep cold you do in Iowa - I have the standard inverter model. Recommend you look into the low ambient models (HYPER HEAT?) no matter what manufacturer you use.

What is your insulation like???? That is a big factor.

But if I am reading it correct I would install an 24k Mr. Cool mini split in the main shop portion and a 12k unit for the office and storage sections.

Dependent upon layout you could do a multi zone unit just depends on how one could run the lines to the heads from the main unit.

Depending upon your current electrical situation that will likely be the most difficult part is getting the proper power to the unit.
Other than that the mini split install is super easy.

We had a 24k unit (Durastar brand) installed last spring for a 600sq ft family room that opens to the rest of the house. Cost was $3500 for a basic install with a single head unit.

Our electric bill dropped about $100-150 per month and the house will freeze you out. Heat works well, too. Very quiet and trouble free so far. Totally satisfied.

I've used the MrCool DIY mini-split in a very similar setup.

I just put in a 2 unit Mr Cool for my gameroom and master bedroom. Install was very easy(DIY), very quiet, they work very well. I can't speak to the cost as before we had no air conditioning, and heat was off space heaters. My two rooms are extremely comfortable now. Wife is totally happy. I love them so much I ordered 3 more for other parts of my house. They show up next week. My house is in colorado and built in the 70's, so no air anywhere.

My sister has two 550 square foot tiny houses with 2 head mini split systems that work great summer and winter (Texas). Systems have been working well for 8 years.

I wanted to retrofit the downstairs of my 1,350 square foot 95 year old duplex with a 3 head system. I thought for sure it would price out cheaper than renovation cost of adding central heat & air. I was surprised to find out the price from 3 vendors turned out to be the same for mini-splits as central hvac.

There's a pretty big price jump to add a 3rd room. If I had 1 or 2 rooms, I would go mini-split all day long. I much prefer them over window units.

I originally had a Mitsubishi 12,000 btu's mini split that lasted 21 years. Very little maintenance, (replaced a mother board and fan motor over this time period.) This was in a sun room with nineteen windows and one door. Seer rating on these units is usually around 22 or 25. They are very efficient units. I have had them bid out from a HVAC company's for supply and install and most bids come in around $3,400.00 to $4,000.00 for one outdoor unit and one indoor head. I just replaced my original unit and purchased a mini split from havacdirect.com and installed it myself. Unit brand was Perfect Air which I had not heard about until searching and reading reviews. Seer ratings were all very consistent and reviews are all pretty good so decided to give it a try. We have had it in since January and have not noticed any change in our electric bill. When using the heat our Mitsubishi would shut down and not run with temperatures dropped below 17 to 20 degrees. (I do think the newer units changed their compressors to operate down to 0 degrees now. This new unit worked and didn't have any problems when our temps were -15 below zero. I think I paid around $1,800.00 for the Perfect Air unit and line set. Very easy install. I know you would be much happier with a mini split for your situation. Since I have installed ours I have purchased 4 more units and installed them for friends and all have worked with out any problems when we fire them up. Hope this helps!

We had a Mits 3 ton Hyper Heat unit installed in May 2022. Using 2 of the 4 heads providing 25k and 9k btu. Installed was $14k with another $1k for new electric service line.

Did have some very cold days well below the -13F HyperCool 100% efficiency heating threshold where heat output was reduced. But overall a huge improvement from no AC and baseboard heat (pellet stove long inoperative). House is 5bed/3bath ~2500ftsq.

Definitely address insulation first or you're just throwing money away.

Appreciate the replies so far.

The structure is insulated. I can't remember how well but it is a steel pole building that I had 40% framed up and finished. There is roll insulation in the walls and blow in in the ceiling. There are no windows, one exterior door, and one door that goes to the open portion of the building.

The two rooms that I would try to cover are side by side. I would not bother with the small storage room. Based on the input regarding lower temps I would probably leave the baseboard heaters in place for super low temps.