Window AC Unit vs. Minisplit System
salamonrs2
| Posted in General Questions on
A 1900 square foot house in Novi MI with all windows facing blazing west sun. Window AC vs minisplit: which is more effecient?
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Replies
How do you define “efficient”?
Lowest first cost?
Lowest operating costs?
Do you put any value on your time and effort required to remove and reinstall the window units every year?
Do you put any value on the view the window unit will be obscuring?
Do you put any value on the appearance of your property?
It has been my experience that window unit tend to have shorter life expectancy.
Walta
I don't have west exposure in my duplex, and my place is smaller than yours (about 1300 sq ft). But the climate (D.C.) is hotter, with an average of 40 days a year above 90 degrees, and a lot of nights that don't fall below 70 degrees.
I can tell you in terms of operating cost, I am very happy with my ducted minisplit system, which only covers upstairs. Before installing the ducted system, we had one window unit in our daughter's bedroom, and a window unit that covered the enclosed sleeping porch/tiny third bedroom. We mostly slept without a/c in our own room & ran the other window units no more than 12 hours a day. With the ducted system, we set it at 80 degrees at hall thermostat (which usually ends up at 77-79 degrees in our bedroom on hotter days in our north facing bedroom with two vents... as the nights get cooler, the low in the room can be 73-75). In July, it ran all day/night every day. Our electric bill was about $85, if memory serves? I think it was only about $10 more than pre-minisplit... and the house is much more comfortable, even downstairs. But it cost a lot to install. Like $15,000, and that doesn't even count the cost of insulating the attic at the roofline so the ducts could be up there.
There are a few window ACs that match or beat low-end mini-splits on efficiency. Midea's U-shaped window units (also sold under the Mr.Cool label) are rated CEER 15, as are some of LG's standard boxy inverter drive window units. The U-shaped Midea is essentially a "mini-split in a can", designed to fit in a double-hung window, with the sash sliding down between the outdoor half and indoor half, with a very wide modulation range. The LGs don't have the modulation feature, but using highly efficiency inverter drive blowers & compressor they're still right up there on raw efficiency. Both are cooling-only, whereas a mini-split heat pump can be highly efficient both as a heater and as an air conditioner.
The hand held remote that comes with the Midea is exactly the same one that comes with several Midea & Carrier mini-split heat pumps- complete with a "Heating" mode option on the remote, which is a bit of a tease since the window units are cooling only.
The advantage of a window unit is that you can drive to the hardware store and grab one — install it in 5 minutes, and be done. But the cost is a machine that is often louder, uglier, and more intrusive (takes up an outlet, interferes with window coverings) than you would like.
The advantage of a minisplit system is that you can keep your windows fully closed in summer, get full light, and probably condition a bigger space, but at the cost of installation (time and money), and sacrificing some wall space, permanently.
If your minisplit is also a heat pump, that might help in those Michigan winters, so that's a plus for that idea. Having to use less heat through your existing furnace system (probably gas?) is always a win from an environmental point of view, even if it's cost-neutral.