For someone who wants a true plug-together install with no tools beyond a drill, and a warranty that survives it. Expect to pay well over the price of a flare unit with the same cold-weather output.
Price checked October 21, 2026. As an Amazon Associate we earn from qualifying purchases.
The rating comes from 5 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 | 18,000 Btu/h |
| Heating at 47 °F | 18,000 Btu/h |
| Heating at 17 °F (max) | 20,300 Btu/h |
| Heating at 5 °F (max) | 12,800 Btu/h |
| Heat kept at 5 °F | 71% |
| Price per 1,000 Btu/h at 5 °F | $227 |
| Efficiency (certified) | |
| HSPF2 (Region IV) | 11.5 |
| SEER2 | 22.5 |
| EER2 | 13.7 |
| COP at 5 °F | 2.44 |
| ENERGY STAR | ENERGY STAR Cold Climate |
| AHRI certificate | 216032545 |
| Operating range | |
| Heats down to | -13 °F |
| Cooling range | -13 to 122 °F |
| Installation | |
| Line set connection | Quick-connect (no vacuum pump) |
| Line set | 25 ft included, up to 75 ft |
| Voltage | 230 V |
| Refrigerant | R-454B |
| Indoor unit | DIY-18-HP-WMAH-230D25-O |
| Outdoor unit | DIY-18-HP-C-230D25-O |
| Build | |
| Indoor noise | 19–54.5 dB(A) |
| Outdoor noise | 58.5 dB(A) |
| Wi-Fi | Built in |
| Room size (maker) | up to 800 sq ft |
| Weight | indoor 35.5 lb / outdoor 93.5 lb |
| Warranty | 7 yr compressor, 5 yr parts |
| Warranty with DIY install | Yes |
The best-value quick-connect line: the same certified system as Pioneer’s Quantum Ultra, close to Della’s Optima, without the vacuum pump, for the same price or a few hundred dollars more.
Amazon $1,679A low price for a self-installer who owns or will rent a vacuum pump. The Klimaire DIY is the same certified system with quick-connect lines, and Della’s Optima has near-identical ratings for less.
Pioneer Mini Split store $1,538A middle step between MrCool’s Select and DIY 5th Gen: quick-connect and a fair warranty, but it loses much of its heat in a cold snap. Best for mild winters.
MRCOOL DIY Direct $1,806Compare the MrCool DIY 5th Gen 18,000 BTU 230V with any other DIY mini-split →
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