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Mini split vs. window AC
Updated July 2026
For a single hot room, these are the two serious answers. One costs five times more up front and is usually cheaper by year ten. Whether year ten matters is the actual question.
The ten-year math, roughly
Take a 350 sq ft room, a 9,000 BTU load either way. Ballpark 2026 numbers:
| Window AC | Mini split (DIY) | Mini split (installed) | |
|---|---|---|---|
| Equipment | $250–400 | $800–1,400 | $800–1,400 |
| Installation | $0 | $0–200 (materials) | $1,500–3,000 |
| Efficiency (typical) | CEER 11–15 | SEER2 16–22 | |
| Summer power cost, ~10 yrs | $1,300–1,800 | $800–1,200 | |
| Heats in winter too | rarely | yes (heat pump) | |
| Typical lifespan | 8–10 yrs | 15–20 yrs | |
The window unit wins the first summer by a mile. The mini split claws it back through efficiency, lifespan, and doubling as winter heat, if you stay long enough and if installation doesn't blow the budget. A pro install of a single head can cost more than the hardware; the pre-charged DIY kits are what changed this comparison in the last few years.
What the table can't show
- Noise. No contest. A window unit puts the compressor in the room with you (50–60 dB); a mini split leaves it outside and the indoor head whispers at 20–30 dB.
- The window. The window unit costs you the window: light, the view, the ability to open it, and, on ground floors, a security hole. The mini split costs you a 3-inch wall penetration and a box on an exterior wall.
- Renting. The window unit goes in without permission and leaves with you. That alone decides it for most renters.
- Permanence. The mini split is a fixture that adds resale appeal; the window unit reads as a stopgap.
The short version
Renter, short horizon, or tight budget: window AC; size it with the window calculator. Homeowner, hot summers, room you'll use for years, or you want winter heat too: mini split; size it with the mini split calculator. If the room has no usable window, the decision has been made for you.