Mitsubishi Hyper-Heat FX 12,000 BTU
#1 in 12,000 BTUFull review
Mitsubishi’s flagship cold-climate system: it makes more than its rated heat at 5 °F and keeps heating to −22 °F. For a home that relies on it as the main heat through a cold winter.
The Mitsubishi Hyper-Heat FX 12,000 BTU is the better mini-split overall, rated 4.9 to 3.8. The Mitsubishi Hyper-Heat FX 12,000 BTU leads on cold weather and efficiency.
LG Art Cool Mirror 12,000 BTU
#15 in 12,000 BTUFull review
For mild to moderate winters: it heats only down to −4 °F and loses some of its heat in deep cold.
Prices were last checked October 21, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Mitsubishi Hyper-Heat FX 12,000 BTU for cold weather (keeps 123% of its heat at 5 °F, heats down to -22 °F vs keeps 74% of its heat at 5 °F, heats down to -4 °F) and efficiency (12.4 HSPF2, 29.9 SEER2, COP 2.20 at 5 °F vs 10.5 HSPF2, 22.5 SEER2, COP 1.99 at 5 °F).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every 12,000 BTU mini-split; a clear win is highlighted. How we rank explains each one.
| Factor weight | Mitsubishi Hyper-Heat FX 12,000 BTU | LG Art Cool Mirror 12,000 BTU |
|---|---|---|
| Overall rating | 4.9/5 | 3.8/5 |
| Cold weather 40% | 100 keeps 123% of its heat at 5 °F, heats down to -22 °F | 42 keeps 74% of its heat at 5 °F, heats down to -4 °F |
| Efficiency 30% | 93 12.4 HSPF2, 29.9 SEER2, COP 2.20 at 5 °F | 69 10.5 HSPF2, 22.5 SEER2, COP 1.99 at 5 °F |
| Warranty 20% | 100 10-year compressor, 10-year parts | 100 10-year compressor, 10-year parts |
| Noise 10% | 95 indoor unit from 20 dB(A) | 90 indoor unit from 21 dB(A) |
Specifications
| Mitsubishi Hyper-Heat FX 12,000 BTU | LG Art Cool Mirror 12,000 BTU | |
|---|---|---|
| Capacity (certified) | ||
| Size (nominal) | 12,000 BTU | 12,000 BTU |
| Cooling at 95 °F | 12,000 Btu/h | 12,000 Btu/h |
| Heating at 47 °F | 13,200 Btu/h | 13,600 Btu/h |
| Heating at 17 °F (max) | 18,200 Btu/h | 12,400 Btu/h |
| Heating at 5 °F (max) | 16,200 Btu/h | 10,000 Btu/h |
| Heat kept at 5 °F | 123% | 74% |
| Efficiency (certified) | ||
| HSPF2 (Region IV) | 12.4 | 10.5 |
| SEER2 | 29.9 | 22.5 |
| EER2 | 15.4 | 12.8 |
| COP at 5 °F | 2.20 | 1.99 |
| ENERGY STAR | ENERGY STAR Cold Climate | ENERGY STAR Cold Climate |
| AHRI certificate | 215611126 | 215413008 |
| Operating range | ||
| Heats down to | -22 °F | -4 °F |
| Cooling range | 14 to 115 °F | 14 to 118 °F |
| Installation | ||
| Installed by | Professional (sold through installers) | Professional (sold through installers) |
| Line set connection | Flare fittings (vacuum pump needed) | Flare fittings (vacuum pump needed) |
| Line set | up to 65 ft | up to 82 ft |
| Voltage | 230 V | 230 V |
| Refrigerant | R-454B | R-32 |
| Indoor unit | MSZ-FX12NL | KNUAK121A |
| Outdoor unit | MUZ-FX12NLHZ | KUSAB121A |
| Build | ||
| Indoor noise | 20–44 dB(A) | 21–41 dB(A) |
| Outdoor noise | 49 dB(A) | 47 dB(A) |
| Wi-Fi | Built in | Built in |
| Weight | indoor 31.4 lb / outdoor 89 lb | indoor 22.7 lb / outdoor 68.8 lb |
| Warranty | 10 yr compressor, 10 yr parts | 10 yr compressor, 10 yr parts |
| Warranty with DIY install | No, a licensed installer is required | No, a licensed installer is required |
| Released | 2025-02 | - |