Window AC vs mini split: which costs less to run?
A mini split costs less to run: about $94 a year for the Klimaire DIY 12,000 BTU, against $141 for the TCL T12WV9S window AC. The window AC costs far less to buy ($490, against $1,759 to $2,959 for the kit and an electrician), so the window AC is still cheaper after 10 years. Amazon prices read November 11, 2026.
Which to buy: TCL T12WV9S if you rent or only cool in summer. Klimaire DIY 12,000 BTU if you own the home and want winter heat too. MRCOOL DIY Select 12,000 BTU if you can’t add a 240-volt circuit; it is listed for a 120-volt circuit.
BTU is cooling power. CEER (window ACs) and SEER2 (mini splits) are efficiency scores; higher means a lower power bill. A 240-volt circuit is the heavy-duty kind an electric dryer uses; a normal wall outlet is 120-volt.
Buy either one for a 12,000 BTU room
12,000 BTU cools 450 to 550 sq ft. Running cost: 1,000 hours a year, 18.83 cents per kWh.
Window AC
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Check price on AmazonTCL T12WV9S
Most efficient on Amazon at this size · $489.99 on Amazon · about $141 a year to run (CEER 16)
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Check price on AmazonBLACK+DECKER BD12NWES
Lowest price on Amazon at this size · $488.51 on Amazon · about $151 a year to run (CEER 15)
DIY mini split kit
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Check price on AmazonKlimaire DIY 12,000 BTU
Lowest price · $1,459 on Amazon · about $94 a year to run (SEER2 24) · 25 ft of line included · needs a 240-volt circuit
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Check price on AmazonMRCOOL DIY Select 12,000 BTU
Next lowest price · $1,549 on Amazon · about $129 a year to run (SEER2 17.5) · 11.5 ft of line included · listed for a 120-volt circuit
A DIY kit has pre-charged lines that click together. It needs no HVAC contractor, only an electrician if you must add a circuit.
Yearly running cost, by size
| Size | Window AC | Mini split | Mini split saves |
|---|---|---|---|
| 12,000 BTU | $151 | $98 | $53 |
| 18,000 BTU | $226 | $154 | $72 |
| 24,000 BTU | $340 | $212 | $128 |
Each figure is the middle certified model at that size (the picks above run $141 and $94, not these middle figures): window ACs from the ENERGY STAR and DOE room-AC list (cooling rated by CEER), mini splits from the certified heat-pump list (rated by SEER2). Cost is 1,000 hours of cooling a year at 18.83 cents per kWh, the average U.S. residential rate we use site-wide (EIA). The mini split row matches the yearly-cooling column on the mini split cost page. Run 500 hours and every figure halves; run 1,500 and it is one and a half times as much. Window ACs above 12,000 BTU are less common, so the 18,000 and 24,000 BTU window rows use the few certified models that exist.
Cost over 5 and 10 years, purchase included
| 12,000 BTU option | To buy | Per year to run | 5 years | 10 years |
|---|---|---|---|---|
| Window AC: TCL T12WV9S Price on Amazon | $490 | $141 | $1,196 | $1,902 |
| DIY mini split kit plus an electrician: Klimaire DIY 12,000 BTU Kit $1,459 on Amazon plus a $300 to $1,500 circuit | $1,759 to $2,959 | $94 | $2,230 to $3,430 | $2,701 to $3,901 |
| DIY mini split kit, 120-volt: MRCOOL DIY Select 12,000 BTU Kit $1,549 on Amazon. Electrician work is not included: our sources price a circuit only for the 240-volt kit | $1,549 | $129 | $2,195 | $2,840 |
| Mini split installed by a pro, one zone Full installed price | $2,800 to $5,200 | $98 | $3,289 to $5,689 | $3,778 to $6,178 |
Total is the purchase price plus running cost for that many years. It counts no replacement and no repair. The Klimaire DIY 12,000 BTU saves about $47 a year on power over the TCL T12WV9S ($141 against $94); the middle models in the size table differ by $53. At that rate it takes about 27 years to repay its higher price at the low end of the circuit cost. Circuit cost is $300 to $1,500 when the panel has room (PickHVAC, Oct 7, 2026). The installed range of $2,800 to $5,200 for one 12,000 BTU zone is from HomeGuide and TLS Air Conditioning, as quoted by FixItCost (checked Oct 20, 2026). A mini split also heats the room, so it can replace a space heater as well. See what a mini split costs installed and the ranked mini splits.
Which one fits your room? Six questions
1. Do you own this home, or rent it?
2. Should it heat the room in winter too?A mini split is a heat pump, so it does both. A window AC only cools.
3. How long will you be in this home?
4. Is quiet critical? Is this a bedroom?
5. Does the room have a standard up-down (double-hung) window?Crank-out (casement) windows can't take a standard window unit.
6. What's the realistic budget for fixing this room?
Window AC and mini split side by side
| Window AC | Mini split (ductless) | |
|---|---|---|
| Cost to run, 12,000 BTU | $151 a year (middle certified model, CEER 15) | $98 a year (middle certified model, SEER2 23.1) |
| Cost to buy | From $488.51 on Amazon (lowest of our two picks) | DIY kit from $1,459 on Amazon (lowest of our two kits), plus an electrician if you need a circuit; $2,800 to $5,200 installed by a pro |
| Heats in winter | No (cooling only, rare exceptions) | Yes, it is a heat pump |
| Noise in the room | The compressor is in the window, with you | The compressor is outside, so the indoor unit is usually quieter |
| Renter-friendly | Yes, it installs and leaves with you | Rarely, it is a permanent install |
| Window required | Double-hung window | No window needed, an exterior wall |
Common questions
Which costs less to run, a window AC or a mini split?
The mini split. At 12,000 BTU and 1,000 hours of cooling a year, the middle certified mini split costs about $98 a year and the middle certified window AC about $151, at 18.83 cents per kWh. The two picks above cost $94 (Klimaire kit) and $141 (TCL window AC).
Is a mini split cheaper than a window AC over 10 years?
No. For one 12,000 BTU room the window AC costs $1,902 over 10 years including the purchase. A DIY mini split kit with an electrician costs $2,701 to $3,901, and a pro install $3,778 to $6,178. The mini split uses less power and also heats the room in winter, but it does not make up its higher price in 10 years.
Can a window AC heat a room in winter?
Most cannot. A standard window AC only cools. A mini split is a heat pump, so one unit heats and cools.
Is a mini split quieter than a window AC?
Usually. A mini split keeps its compressor outside, so only the indoor unit is in the room. A window AC has its compressor in the window, with you. We have no certified noise ratings, so for a bedroom compare the sound level the maker lists before you buy.
What if my window is a crank-out (casement) type?
A standard window AC needs an up-down (double-hung) window. With casement windows your options are a casement-specific unit, a through-the-wall unit, a portable AC, or a mini split.
Efficiency ratings are certified CEER (ENERGY STAR and DOE room-AC data) and SEER2 (AHRI and ENERGY STAR). Running costs are our computation from those ratings at 1,000 hours a year and 18.83 cents per kWh (EIA). Installed prices and the circuit cost are from HomeGuide, TLS Air Conditioning and PickHVAC, as on the mini split cost page. Amazon prices are buy-box reads from the day shown beside the first price. See methodology.