Fw: DIYing Our Ductless Heat Pump Install Was Hard but We Saved $7,000
Jonlin, Duane
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Duane Jonlin, FAIA
Energy Code and Energy Conservation Advisor
P.O. Box 34019, Seattle, WA 98124-4019
P: 206.233.2781 | duane.jonlin@seattle.gov
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Helping people build a safe, livable,
and inclusive Seattle. |
Sent: Thursday, November 20, 2025 9:01 AM
To: Jonlin, Duane <Duane....@seattle.gov>
Subject: DIYing Our Ductless Heat Pump Install Was Hard but We Saved $7,000
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Last summer I did something very ambitious. I DIY installed a ductless heat pump system almost completely solo. And it wasn’t just one simple ductless system, it was five indoor ductless heat pumps (3 of them on a second floor) and two outdoor units. I’d never done anything like it before but wanted to try out how accessible heat pumps are for the DIYer and how much money we could save. Spoiler alert, it was really challenging and consumed about a week of my life, but I was able to complete the job successfully and saved around $7,000. Why DIY a heat pump installWhy would I take on something as ambitious as DIYing a ductless heat pump install? First, I was curious about how realistic, accessible and user-friendly a DIY ductless heat pump kit was. DIYing a heat pump water heater was pretty doable, would a heat pump be the same? I also wanted to learn more about the ins and outs of these systems and the overall process of installing them. But saving money was probably the biggest reason. In 2021, we’d purchased a ducted, whole house heat pump on one side of a family duplex in Cleveland for $12,500.
This has been a great system but we wanted to see if I could save money on the duplex’s other side which had an ancient, 35 year old gas furnace on its last legs. We had gotten quotes for ductless heat pump installations for over $15,000 in 2021, and didn’t feel like we had the budget to spend that much money on replacing the heating and cooling system on the other side of the duplex. A DIY kit looked about half the cost and was very tempting. My third and final reason was that I wanted to have cooling directly in the upstairs level of this side of the duplex. Our whole house heat pumps on the other side (along with really any AC) can struggle to cool the upstairs floor of the house. So we elected to go for lots of ductless units to bring cool air directly upstairs. Buying the DIY Ductless Heat PumpsI decided to make the leap and ordered a DIY Mr. Cool heat pump system from an online distributor last summer. The total cost for two outdoor units and five indoor units was $6,500, a substantial savings though we would spend an additional $2,000 on some labor help and parts. The system arrived in boxes on a big pallet in mid-August.
Now, I should mention that I consider myself a 4 or 5 on a scale of one to ten for being a handy DIYer. I’ve done a lot of projects on my house in the past, but don’t have great knowledge, craft or tools. To prepare myself for this ambitious project, I watched a lot of videos ahead of time and read over the instruction manuals carefully. I also tried to find someone with more HVAC experience to assist or possibly lead in the installation. Here I learned an important lesson, it was next to impossible to find additional help once we’d gone down the path of a DIY install. I called a half dozen HVAC contractors but all of them expressed a worry about being liable for equipment that they didn’t order. None of them wanted to help out on our project. I also figured that these companies probably make a significant margin on the equipment and aren’t interested in installations where they don’t provide it. So I nervously set off to undertake this massive installation solo. Indoor Unit InstallationInstalling a ductless heat pump system involves first drilling a three and a half inch hole through the house to pass the refrigerant lines and communications cable for every indoor unit. This is, needless to say, intimidating. My first couple holes went well but after the first two, the process started taking forever. I later learned that the hole saw I was using was almost completely stripped and so by the final hole or two were brutal. This is a hazard of DIYing. Without a lot of deep background knowledge in tools, little mistakes can slow a project down considerably if you don’t have the experience and knowledge to recognize what’s going on and adjust.
Once the holes were done, I installed the indoor unit on a mounting bracket and passed the communications cable and refrigerant lines out of the house. This all went reasonably well and I felt maybe a little too cocky after installing the indoor units thinking to myself, “wow, I can drill a hole into a house and mount an indoor unit, I must be pretty handy.” There was a lot of hardship ahead however. Outdoor unit, refrigerant and condensate lines
Turning my attention to the outdoor units, I mounted brackets to the house to hold them. Here I had help from a handyman neighbor. Next, I connected the refrigerant lines from the indoor unit to the outdoor unit. The trick with a DIY heat pump kit like Mr. Cool, is that you have to measure and order refrigerant lines that are long enough to connect each indoor unit to an outdoor unit. The pre-charged refrigerant lines come in various sizes and you will probably have extra (because you don’t want to order too little) and so then must coil it next to the outdoor unit. You also run a condensate line and wire the power and communications cable to the outdoor unit. The big challenge for this part for me was installing the housing that holds (and goes over) the refrigerant lines, but this ordeal was self-inflicted. Rather than buying the Mr. Cool housing which I thought was too expensive, I bought a generic competitor to save money and this ended up being a mistake. It was very challenging to fit the refrigerant lines in the generic housing as they were probably too small for my job. I ran out of time and had to hire a handy person to finish installing the housing. They did a nice job but cost $1,000. Wiring the outdoor unitFinally I had to run power from the panel to the outdoor units. I needed two outdoor units for my five ductless heat pumps, and luckily one of them was able to connect to the old air conditioning electrical box. I had to run a new wire for the other outdoor unit. I had never done this before and here I “got by with a little help from my friends” as my amazing electrical engineer neighbor Glen took pity on me and helped out with this process as I was running out of time. We spent one evening working until midnight to finish the electrical part of the project. One big challenge was that the electrical wires that Mr. Cool recommended were too big to connect to the unit. Glen thought of a work around and if I hadn’t had Glenn’s help I would have probably spent a significant time with customer support from Mr. Cool.
After probably 60 to 70 hours of work the units were installed and have been working really well for almost 18 months now. Guests in our Airbnb say they love having heat pumps in every room. Interestingly enough, I get a side by side comparison of the ducted vs. ductless heat pumps on either side of the duplex. In my opinion, the ductless work better for two big reasons.
Final thoughtsDIYing your ductless heat pump installation can be very challenging. If you are someone like me at a four or five out of 10 handiness level, you can probably do it but it will take a while and will be hard. My big mistake was that my first experience installing ductless heat pumps involved so many indoor and outdoor units on a two-story house where I had to get up and down a ladder many times. I might sing a different tune if I had tried this with one unit in a converted garage.
On the good side, I learned a ton about heat pumps and I was able to save around $7,000 on the install. My total project cost came to $8,767 (not including my time of course) for a nice system that is both clean and efficient.
I do not think I would do such an extensive system again but would consider our one or two indoor unit system in the future. Have you DIYed your heat pump installation? Let us know your experience in the comments below. Electrify Now is free today. But if you enjoyed this post, you can tell Electrify Now that their writing is valuable by pledging a future subscription. You won't be charged unless they enable payments.
© 2025 Joe Wachunas
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