Installing a Mini-Split AC in a Brooklyn Apartment
by Malte Skarupke
Last year, 2024, we replaced four PTACs with a mini-split AC. I’ve been asked about it often enough (by neighbors, coworkers, friends) that I decided to write up the experience. Hopefully it’s useful for you, too.
Overall this cost us about $40k, including the cost for closing up the PTAC holes. We’ll probably never make the money back on electricity cost savings, so the main benefits are that we have more quiet and more stable temperatures now and overall I’m glad that we did it.
(I’ll use the term “heat pump” and “AC” interchangeably. Every “AC” mentioned in here can do both heating and cooling)
Prologue
We bought this apartment at the end of 2023. The old owner had installed four brand new PTACs at the beginning of 2023 to get ready for selling the apartment. I don’t know the actual reason for this, but I assume the old heaters were nearing their end of life or were broken already. In any case the new thing they installed were really bad. They’re by Islandaire and they’re loud and they are warm-weather heat pumps only. Meaning as soon as you get close to freezing, they switch to backup heat, which was just electric resistive heating. This makes no sense for two reasons: 1. It gets cold in NYC, and 2. we actually had gas pipes leading to these ACs so the backup heat should really be gas. In the winter we would run on backup electric heat for months.
The most expensive electricity bill that year was $1200. Which is a lot for a three bedroom apartment with neighbors above, below, to the left and to the right.
And to top it off the PTACs had been installed wrong so they would drip inside the apartment and warp the floors. We noticed and fixed this fairly quickly but at that point they had been running for months without anyone living in the apartment and the floors were already damaged. Also apparently the old owners had sanded the floors while keeping the ACs running, so the filters were completely clogged by sawdust, and even after we cleaned those, one of the ACs never fully recovered and broke completely within a year. In theory there was warranty on these, but we could only ever get the person who installed them to come out once. After that we were completely ghosted. We debated suing but we didn’t actually want to keep these ACs for a second winter, so why go through all the trouble to force a repair on a thing that we didn’t even want?
So we had to get a new AC before the winter.
Research
I live in a second-floor apartment that only has windows in the front and the back, with no roof access. I have access to a backyard but there is no way to get large machinery back there. So geothermal heat pumps were impractical, and the only real option is to go with a regular old mini-split with one large outdoor unit in the back and four terminals inside, with lines (pipes?) running through the walls.
You’re supposed to get a $7k rebate because the government incentivizes installation of heat pumps. Unfortunately we didn’t qualify because you need to switch from fossil fuel heating, which we no longer had… (so the fact that the old owner had replaced the old ACs had not only cost them, it also cost us $7k)
I probably did not look into enough contractors. Obviously Alex Wilson, the guy who had installed the old AC, was straight out. I had asked our upstairs neighbors, who had already replaced their PTACs with a mini-split. Their advice: “our guy wasn’t that good, you should probably go with someone else” (they were actively dealing with water damage in the walls caused by their mini-split system when I asked). I asked a friend who had just renovated their apartment, and their advice was “our guy wasn’t that good. You should probably go with someone else.”
I had reached out to Mitsubishi on their website to see which contractor they recommend. The person who came over seemed competent, said they would take care of everything and quoted us $53k, twice as much as our upstairs neighbors had paid. I reached out to Ice Age because they had a good reputation. Their boss also seemed good (he pointed out that we didn’t qualify for government rebates) and quoted us $31k but that didn’t include taking out the old PTAC and fixing up the holes.
Luckily our upstairs neighbor had a good contractor who had patched up their holes. His work seemed good and we wanted some other work done anyway. (we had some metal bars in front of our windows that we wanted taken out)
So we decided to go with the combination of Ice Age plus the contractor to fix up the holes. The $53k guy had told us that we should really go for the “designer” indoor unit (“you don’t want those other ones, they’re round”) so we asked about it and Ice Age said that they would provide us with those at no extra cost. So they probably had good margins at $31k.
I’ll let you guess what my answer is now when people ask me about our contractor.
Installation
This was supposed to take a week and a half, two weeks max. It took more than a month. I was introduced to the boss and to the guy who would supervise the work. I wouldn’t see the boss again until everything was finished. I saw the supervisor maybe twice.
On the first day we got a message saying there was a problem at another work site, so there would be delays and they would start a little later. We had moved some furniture around to allow work on certain walls and moved it back and waited. This was a sign of things to come.
Work moved at a sluggish pace. On the actual first day a guy would come and cut some holes into the drywall. On the second day some other people would come and try to put some pipes into those holes. Then they would cut all the holes bigger (which takes as long as cutting the holes in the first place) because they weren’t the right size. This went on for days.
The workers always cleaned up after themselves and did a good job at that, but since there is always drywall dust in the air, you just can’t clean everything up. This bothered my wife a lot and she did a lot of swiffering and wiping of counters in these weeks.
This moved slowly for more than two weeks. Usually a group would work the full day, but some day you’d just get one guy for an afternoon. There was at least one day where nobody showed up because the workers were needed elsewhere. Eventually we had those insulated AC-lines leading from the back of the apartment to the front, when we found out that they actually didn’t have the right units. They said the shipment from Mitsubishi was delayed and maybe they’d have the units the next day or the day after, but the wait took a week where we had lots of holes in the drywall. Luckily we still had the old AC units installed and working.
In all this there are lots of little decisions to make. On which wall should the indoor units be installed? Where exactly should the soffit for the pipes run? Where do you put the branch box on the inside? Where does the pump go for pumping out the condensation? Where does the drip pipe exit for the condensation? The workers from Ice Age had good opinions on this but it still felt like I should be involved in all those conversations. E.g. I was able to suggest the most logical spot for the branch box, and I got them to make one soffit a little bit smaller than they had planned to make it, (I just asked them to open up the drywall above it) and we really didn’t want the living-room AC on the wall that they suggested, so it went right next to that spot.
Eventually both the indoor and outdoor units arrived and were installed. We have stairs leading down to the backyard and I thought it would make sense to put the outdoor unit under those. It should have fit according to the measurements. Unfortunately there wasn’t enough room between the fence and the stairs to turn the AC. We could have probably dismantled the fence temporarily and moved the AC, but we ended up just putting the unit next to the stairs. This means it’s a little harder to get under the stairs (e.g. to service the AC or to get to the water hose) but it also meant that our ground-floor neighbors don’t have a window blocked that’s under the stairs.
The electrician work to put power cables outside was included in the price. I also asked them to put a CAT8 cable outside for me while they were at it, which they did for free after I provided the cable. They had more decisions to make and didn’t ask me, so put some cables in the way of where the AC workers had wanted to put the AC pipes (so now the AC pipes are a little less neat) and they did slightly nonsensical work on the breaker panel (now one half of the panel is crammed while the other half is mostly unused).
Overall everyone actually did pretty good work. I once pointed out that some drainage pipes for condensation didn’t run strictly downward the entire time, and the workers fixed that pretty quickly. And I think that was the only complaint I had. After the ACs were installed the workers closed up all the walls really well, and painted with paint that we had to provide. You can not tell where the work was done at all.
As far as I can tell they did not do a test run before closing the walls, which seemed very brave to me. But when it came time to turn on the new units, they worked flawlessly on the first try. And it’s now been almost a year and I haven’t had any big issues with them. They’re heating in the winter and cooling in the summer.
Taking out the old ACs
We still had the crappy old PTACs installed though. To take them out we went with the contractor that was recommended by our upstairs neighbor. I think the price was like $9k. Lower at first, but then some extra charges added up as the work went on. This took another two weeks and was actually more complicated than the installation of the new AC.
The old units could just be pulled out, at which point you have giant holes in your walls. They closed the hole up on the outside with some a board that might be sheetrock (I don’t know my construction materials), then one board of insulation and then drywall on the inside. It didn’t feel like enough and in hindsight I wish I had insisted that we fill up the space with insulation material. Just for peace of mind because insulation material is very cheap.
One limitation was that we had to maintain the same visuals as the rest of the building. So we kept the grilles on the outside where the holes used to be. We actually have a window behind one of them, which is much better than just having a wall. (except that this summer we had ants crawling in through a crack by that window…)
Before closing up the holes we had to shorten and cap the old gas pipes, pictured above. (the thing with the silver cap and a red valve) Otherwise they’d forever be sticking out of the wall. The contractor doesn’t do this since only plumbers touch gas pipes. So I asked our building and they recommended a plumber who came right away on the same day. He looked at it, asked us to expose more of the pipes, and said we should make sure that we get the hourly rate, which was like $275/hour. Then he said he’d be back the next day once we had exposed more of the pipes. Our contractor complained a little about the extra work for exposing more of the pipes but then decided to just charge us a little extra for it. (once again more decisions to make. Is it OK to just expose a bit of the pipes or do you want to hide them entirely? I went with hiding them entirely and am glad we did)
When I called the plumber company to confirm that they’d be back the next day, they quoted me $1050. I said that the plumber told us we should get the hourly rate. That caused a short discussion on the other end, for which the conclusion was that no, this would cost $1050. I said I’d have to call around. They then send me a quote for $875 for 2.5 hours of work at $350 per hour. At this point it’s the evening and the pipes need to be plugged the next day. I start calling random plumbers found on google. One of them works late and comes over. They quote us $900. In the meantime I’m texting my contractor who says he knows a plumber, and if that plumber can’t do it, the contractor would do it himself for $300. I tell that to the plumber who is in our apartment and he calls his boss. “they say they have someone willing to do it for $300…” after which they offered to do it for $350 which I accepted. (I also had another offer from the original plumbing company in my email to do it for $700 but I’d have to accept right away otherwise it’s back to $875)
The actual work to cap four pipes takes like 30 minutes. You literally turn off the gas, unscrew the pipes, screw in plugs, turn the gas on again, and do a final check to make sure the plugs are tight. Maybe it took a little longer because one of the pipes was a little stuck, but certainly not a full hour. And the plugs probably cost like $5 each. This is easy money for plumbers, and they’re trying to rip you off because they know that they can hold up the entire project. If I hadn’t gotten those pipes capped, we couldn’t have started on closing the holes, and my contractor hates waiting because he can’t easily fill the wait time with useful work on other projects.
Then more decisions to make about what shape of window sill to install (the old PTAC acted a bit like a window sill) and how to paint or stain the wood and some details to decide around the new baseboards.
Overall I’m pretty happy with the work. The big regrets are that the window in the living room has enough gaps around the outside so ants can come in, and I wish we had more insulation in the walls.
Results
How much money did we save? Not as much as expected. The most expensive month in the next winter was $1000. I installed an energy monitor and confirmed that this is almost entirely due to the AC cost. Though this isn’t a totally fair comparison since we have an Au Pair now, so there was one more person living here, and what used to be our office (with heat turned off at night) is now someone’s bedroom (with heat turned on at night). Also the old AC couldn’t actually get the living room properly warm in the winter, the new AC can.
Still when I ask Claude.AI to double-check the math on our power consumption, it thinks we have an incredibly leaky apartment. Like ridiculously off the charts. This also lines up with my inability to run a humidifier in the winter. I got the biggest, baddest humidifier I could find, and it barely makes a difference. I’m still trying to figure out what causes that. We do have bad aluminum-framed windows, and we also have no insulation in our ceiling, so maybe all the heat goes to our upstairs neighbors. I also have various fans sucking air out of the apartment non-stop, one in each bathroom and one from the clothes dryer (when I hold an incense stick up to it I can see it pulling in air even when it’s not running), plus I have an elevator that opens into the apartment which might have a chimney effect.
But overall we’re pretty happy with the new ACs. The biggest thing for me is the noise. The old PTACs were just so loud every time they turned on. The second biggest thing is that they actually reach and keep the temperature you’re setting. The old PTACs would wait until it feels too cold, then turn on with a terrible noise, heat until it feels too hot, then wait again until it’s too cold. I remember often adjusting the target temperature because I felt either too hot or too cold. So this is a big upgrade for quality of life.
The main downgrade is that the old ACs were hooked up to a Nest system, so I could control them from my phone, and Mitsubishi does not support that, so I actually have to use those crappy AC remote controls. Apparently I can install some wifi extension for $1000 ($250 per unit). I’m thinking of doing that.
That’s all I had to share about this. Hopefully this was useful to you. For now our next project is to replace the sliding patio doors in the back of the apartment because we know those are terrible and are letting in lots of cold air. Maybe I’ll write about that experience next year.
Probably Dance 
Generic advice for thermally leaky apartments is to air seal and insulate and only then replace windows and doors. (Although if the window/door itself is the air leak, that’s the big one.) You might also try getting a Flir thermal camera to see whether you can directly see hot/cold spots. Good luck!
Thanks. I have a really hard time figuring out how big the impact of various problems is. We knew before replacing the PTACs that something was wrong with the apartment, but it made sense to me that the biggest problem would be that a PTAC essentially means you have an open wall. Sure the AC unit is supposed to block airflow, but it’s not exactly great insulation. But then closing those holes made very little difference.
We know that one of the sliding doors has a piece missing that’s supposed to close the gap between the sliding part and the fixed part when the door is all the way closed. So you can literally see through that gap to the outside even when the door is all the way closed. It’s almost an inch-sized hole straight outside that’s hard to close properly, since there are moving parts. It’s still probably less airflow than the PTAC units were…
We still decided to do the doors first because the kids bedroom is really difficult to get steadily warm or cold, even though it’s smaller than our bedroom. And the biggest most likely reason is that sliding door with a hole in it. Except after we put in the order for the new door we had some other construction done and noticed that there is literally zero insulation in the walls to the outside in that room. And in the parents bedroom there is insulation in the wall. (though sloppily done) So maybe that entirely explained the difference. But it’s really hard to figure out which problem is responsible for how much.
I have done a sweep all over the apartment to look for other places where air gets in or out, and I can’t find anything other than the bathroom vents, dryer vent and elevator. The dryer vent was disconnected from the dryer at first so it was literally sucking out air all the time. But even if I close it entirely I can’t measure any difference to heating or humidifier.
I also tried getting a “residential energy assessment” because that’s a thing New York state offers but all the companies I called had some reason why we couldn’t get one. (some didn’t know what it was, even though they’re listed on the website, others said they only work with houses, not apartments, another only works with low-income households)
I’ve been trying to apply programming debugging techniques here but I feel like I both don’t have the right theories and don’t have the right tools. Maybe I’ll try to get a Flir thermal camera this winter, but once again I’m worried that I won’t even know how big the impact actually is of addressing issues that I find with it.
For some reason, your website really don’t want to let me comment. (The first time was hard too.) Anyway..
Yeah, it’s really really frustrating trying to be systematic about this. (I went through the same problem.) It’s even worse because sometimes you have to address multiple issues to really feel the impact. And even then, without running a bunch of regression analysis against behavior, weather, etc, you don’t really know. (This is also why it’s hard to do climate credits around this stuff, even if it’s a darn good idea.) I got a sensorpush thermometer system to try to measure more precisely and found it also to be non-actionable. The Flir will help guide you to hot (cold!) spots to tackle but that’s about it. That said, it’s the only tool that was actually useful for me. That’s why, in the end, you usually end up doing “known useful” things–in rough order: air sealing, insulation, and (last) windows/doors. Flir mainly helps locate air sealing spots (gaps around windows/doors, electrical outlets) and insulation gaps. Air sealing is often as easy as some caulk, a new door threshold, an insulation sock on the floor, etc. Mostly DIY stuff. If you can borrow a super strong fan, you can also fake an air blower test: set it up in your doorway pointing out, and walk around your house feeling for drafts. Hope that helps. Good luck.
Instead of paying so much for the extensions U can use these little Cielo controllers. I use them in my home to connect my Google home to my Mitsubishi heat pumps and they work great.
Thanks! I hadn’t heard of these before. Will try one out.
>I also have various fans sucking air out of the apartment non-stop, one in each bathroom and one from the clothes dryer
Well there’s your problem. The fact that you also can’t humidify your apartment rules out any insulation issues. You need to turn the rate of air cycling way down. Also look into getting an air heat exchanger.
This makes sense to me but I had no luck attacking the problem. Obviously with the PTACs still in the walls I thought the problem was the PTACs. But then things didn’t get better after I removed them. I tried closing all the vents and it also barely made a difference. I still have the bathroom vents mostly closed, but I had to open the dryer vent again. I redid the rubber gaskets on the windows in our living room because the old ones were brittle and leaky, but I didn’t rerun my humidifier tests after that. So I don’t know how much that helped. I also didn’t try closing the elevator. As I said we’re going to replace our sliding doors, and I still want to put insulation in the ceiling.
Basically I have no idea how to be more systemic about this, other than just trying lots of things. Any advice would be welcome.
How would the air heat exchanger help?
It sounds like you had some scammy contractors!
When I got my mini-splits in 2017, the cost for four indoor units and one outdoor unit from Fujitsu was just under $12K. The drywall/painting/patching was separate.
In 2025, we were able to pay Aladdin Plumbing for time ($250/hr) and materials for an expansion tank installation. That $800 you paid was a total racket.
Not gonna lie, I can’t rule that out and I thought I was paying too much. The plumbers were clearly scammy (and I “only” paid $350, not $800) but I had heard similar numbers for the AC from other people I had asked. I paid a little bit more than my neighbors, but not much more. And they had done more research to compare more contractors. So based on my neighbors asking around and me asking around, I didn’t think I could get this done much cheaper. Plus these contractors were busy. I don’t think they were only working part of the crew for fun.
My experience is that Brooklyn prices are just a multiple of what you pay in other places.
My best guess is what happened is that dollar devaluation/inflation increased the price from $12k to $15k, then the government rebates were priced straight in and increased the price for anyone who couldn’t get them, plus I had the patching/painting included which is at least another $1k and maybe demand went up to increase prices further. Factoring all that in $31k is definitely high, but not crazy.
Ah nevermind my estimates. Of course there are official numbers on this and according to Claude.AI prices doubled between 2017 and 2024. So a doubling of the price plus a $7k rebate (that I didn’t get) exactly explains the difference between $12k and $31k, if you assume that suppliers can fully eat up the rebate. If you don’t assume that, I still paid too much, but not crazy too much.
Gosh, that is a massive cost. My mini split in st. louis city cost $5.5k (of course no PTAC removal and also no rebates/credits). also,
Look into Sensibo, it’s a wifi box with climate sensor and an IR blaster that allows control for almost any HVAC system with an IR remote control. Works well for my Fujitsu with HomeKit, whilst the OEM wifi module was only controllable from their app. I looked for some kind of open system or making my own but it does the job well enough. And it notifies when CO2 or TVOC is getting above a set threshold, which is cool…but only if opening a window was an option when Missouri summers are 100ºF and winters are 0ºF ¯_(ツ)_/¯
FWIW, my $12K cost did not include any rebates. I do remember quotes varying a fair bit, and Mitsubishi being more expensive.
Hello! Thank you again for writing this up. This is very helpful to read as someone who is currently embarking on this project. I have a few not-that-helpful things to add:
In case you didn’t already know, I believe you are eligible for a $2000 federal tax credit https://cleanheat.ny.gov/inflation-reduction-act-tax-credits/. My HVAC company (Prime Air) mentioned this to me. I haven’t looked hard into it, though
For whatever it’s worth, I’m currently being quoted $26K for the HVAC work (two condensers — one driving a single indoor unit, another driving three indoor units, all Mitsubishi) and $7K for the electrical work (although we are also doing some additional electrical work to install a 240V outlet in the kitchen so that we can finally get rid of our awful gas stove), which has to permitted
I live in a strict building so we are also paying $7K for a mechanical engineer to pull the mechanical/structural permits and draw diagrams. Both Prime Air and Airinizer recommended the same mechanical engineer, which was a little funny. I guess “HVAC work in a strict condo building in Brooklyn” is a small world
It’s been weirdly difficult to get a licensed master plumber to respond to me. I need to cap some drains (my PTACs are electric, so no gas pipes) as well as the stove gas pipe. I already reached out to three companies, with no replies
Like you I think, I have found LLMs unbelievably helpful for this. Being able to get ChatGPT to find highly rated contractors with specific constraints, read our building’s (super long) alterations guidelines, define words, ask about why heat pumps are so popular now, force me to ask contractors questions I wouldn’t have thought of, etc. has greatly increased my confidence in everything (except I probably should’ve kept getting more quotes — the logistical labor of emailing and calling and texting people really wears a person down, especially if there’s a newborn in the house). The work hasn’t happened yet, so I shouldn’t be counting my eggs before they hatch I suppose
I hate my ten-year old PTACs. I cannot wait for the day they’re uninstalled and carted away. (Prime Air offered to do this for me, which I was pleasantly surprised by?) Mine are a weird custom size. I feel bad just condemning them to a landfill … except they are awful awful technology. They are loud. They require maintenance. I hate that one of the loudest ones we have is in our baby’s room. The loudest one makes the room, the office, unusable and unsleepable in my opinion. The sleeves leak air, like you said. We got quoted $8K to replace them from EcoAir (one of the few companies that can work on these cruddy things), so I’m mentally deducting this from big bill. My wife has a higher tolerance for them, so I do feel like I am being oversensitive