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.
No store we check sells it online; the maker lists where to buy or who installs it.
The rating comes from 4 measured or published factors, each scored 0-100 against fixed reference points for its size. How we rank explains each one.
| Capacity (certified) | |
|---|---|
| Size (nominal) | 18,000 BTU |
| Cooling at 95 °F | 17,200 Btu/h |
| Heating at 47 °F | 17,000 Btu/h |
| Heating at 17 °F (max) | 28,200 Btu/h |
| Heating at 5 °F (max) | 23,600 Btu/h |
| Heat kept at 5 °F | 139% |
| Efficiency (certified) | |
| HSPF2 (Region IV) | 11.1 |
| SEER2 | 25.5 |
| EER2 | 13.1 |
| COP at 5 °F | 2.06 |
| ENERGY STAR | ENERGY STAR Cold Climate |
| AHRI certificate | 215611128 |
| Operating range | |
| Heats down to | -22 °F |
| Cooling range | 14 to 115 °F |
| Installation | |
| Installed by | Professional (sold through installers) |
| Line set connection | Flare fittings (vacuum pump needed) |
| Line set | up to 100 ft |
| Voltage | 230 V |
| Refrigerant | R-454B |
| Indoor unit | MSZ-FX18NL |
| Outdoor unit | MUZ-FX18NLHZ |
| Build | |
| Indoor noise | 27–45 dB(A) |
| Outdoor noise | 52 dB(A) |
| Wi-Fi | Built in |
| Weight | indoor 31.4 lb / outdoor 119 lb |
| Warranty | 10 yr compressor, 10 yr parts |
| Warranty with DIY install | No, a licensed installer is required |
| Released | 2025-02 |
Senville’s top line makes more than its rated heat at 5 °F, heats to −22 °F and carries a 10-year parts and compressor warranty. Sold online, but the warranty needs a licensed installer.
Amazon $1,799.99 Senville $1,799.99ACiQ’s cold-climate line, sold online, keeps most of its rated heat at 5 °F, heats to −22 °F and gets a 12-year compressor warranty once registered. A certified technician has to install it.
Fujitsu’s cold-climate line, with more than its rated heat at 5 °F and very high certified efficiency, for homes heating through a cold winter.
Compare the Mitsubishi Hyper-Heat FX 18,000 BTU with any other mini-split →
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