DIY Mini-Split Heat Pump System

One of the major fails of my house has always been its all-electric nature; every winter I’ve heated with the home’s original electric baseboard heaters – one of the most expensive and inefficient heating options available! When I moved in, I beefed up the insulation in the attic and I’ve spent time making things as airtight as possible, but my electric bills during cold months are always over $200.

Because of my high heating costs, I’ve had an eye on alternative heating technologies for years, especially heating & cooling mini-split heat pumps. Heat pumps are efficient and awesome because they exchange heat from the outside air to your living space. Many mini-splits are marketed and sold solely as air conditioners, but there are many units available that also provide heat. Their high price tags have deterred me in the past, but over the past year I became aware of a number of more affordable units sold in kits where a DIY-install is easier.

After many calculations, borderline obsessive research, and carefully considering a variety of different systems, I decided to pull the trigger and buy one to install myself. My DIY project over the past month has been installing a two zone system for 2 bedrooms upstairs. The install was relatively straightforward (no thanks to the terrible installation manual), and after I had it all installed and ready to go, it only required 2 hours of help from an HVAC professional to get it fired up.

The Mini-Split Install Process

The system was delivered to my house on a palette containing the compressor, two evaporator head units, two sets of pre-insulated copper lines, and a variety of other smaller parts and pieces. The line sets connect to the compressor and evaporator with flare nuts, and also came pre-flared. The compressor was shipped with the correct amount of refrigerant pre-charged.

For the curious, this was the rough breakdown of steps:

  • Identify the ideal mounting spot in each room for the head unit, and then put up the mounting brackets.
  • Drill a slightly downward-angled hole through the wall to the outside in each room.
  • Attach the control/power cable to the electronic connectors on each head unit, and mount the units with the line sets, cable, and drainage pipe threaded through the new hole in the wall.
  • Install mounting bracket on the outside wall for the compressor, and bolt the compressor to the bracket.
  • Install a new breaker in an empty space on your electrical panel and run wiring to the unit (this was thankfully a very short and relatively easy run for me, with a little help from a friend!)
  • Attach the line sets from the head units down to the compressor, making sure to not kink the copper pipes or over/under tighten the nuts.
  • Extend the drainage pipe close to the ground, and bundle the copper pipes, drain pipe, and cable together.
  • Install line set covers around the linesets to give it a nice professional look (optional).
  • Attach the control cables to the proper electronics hookups in the electric panel on the compressor.
  • Hire a professional to do a leak test and vaccuum pump the lines before releasing the refrigerant.
  • Turn on the system and test!

It seems simple as I type up the steps, but I ran into challenges and unknowns that required research at almost every step. I spent a lot of time learning about the electrical wiring and other details about each of the steps, because the instructions were so lousy. Thankfully, the world is full of forums and other helpful tidbits that assisted me in piecing together exactly what needed to be done.

A few times I had to improvise or buy a new tool, and I went up and down the ladder about 200 times, but I got the job done! I am proud to say that the HVAC serviceman who helped me finalize my install was thoroughly impressed with my preparations, and the system is working great with no problems.

The Money

Bids for mini-split systems from HVAC companies ranged from $4,500 to $7,000. My total cost was less than half of the lowest bid. Here’s the breakdown:

Mini-split install kit (Affiliate Link) $1,688
Mounting bracket for compressor (Affiliate Link) $35
Line-set covers (Affiliate Link) $96
Electric supplies $112
HVAC professional leak check and vacuum pump $240 ($120/hour)
Other miscellaneous supplies, tools, and pizza $74

The grand total for the whole project was $2,245. $450 of the kit purchase was paid in Amazon gift cards, earned from a new credit card bonus, so total out of pocket expense was $1,795.

Operating Cost

My original inspiration for the project focused on reducing total heating cost and improving the efficiency of my heating system; since it’s summer time now, I can’t yet say how successful this system will be at reducing my yearly spend on heat, but I believe it will be significant. A happy side effect of this new system is the addition of air conditioning to these two bedrooms. So far, use of the air conditioning during hot afternoons appears to be extremely affordable, as it hasn’t made a noticeable difference in average electricity usage. My hope is that even after using the air conditioning during the summer, this system will still reduce our overall electric usage yearly.

Because I am so interested in exactly how much it will cost to run this system, I am considering buying an electricity monitoring gadget as a dedicated gauge on the mini-split’s circuit. I can’t decide whether it’s worth the purchase yet, so for now I will continue to monitor electric usage, and whether average costs change through the year.

Summary

If you’ve ever considered a mini-split, but were deterred by the cost, I can recommend tackling this as a pretty easy DIY project. I learned a lot through the project, and I am certain that so far AC earned through my own labor is more enjoyable. Check back at a later date for updates on the operating costs through the cold season!

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