Why it matters
The MRCOOL DIY 5th Gen 18,000 BTU 230V is rated at 18,000 BTU of cooling and 18,000 BTU of heating. On the ENERGY STAR room sizing chart that suits about 700 to 1,000 sq ft of average room; the maker says up to 550 sq ft.
Its 22.5 SEER2 ranks 5 of 26 among the mini-splits within about 12% of its capacity that we cover; the most efficient is the Senville Elite 18,000 BTU 230V at 25.6. Heating efficiency is 11.5 HSPF2. The listing doesn't give a low-temperature heating limit, so treat it as a mild-climate heat pump until the maker confirms one. Indoor noise is listed at 19 dB at its quietest setting.
The line set comes pre-charged with quick-connect fittings, so the install skips the vacuum pump and refrigerant handling a standard mini-split needs. It uses R-454B refrigerant, one of the lower-impact A2L refrigerants new systems moved to in 2025. Warranty, per the listing: Eligible for MRCOOL Care Program, 5-Year Limited Parts Warranty, 7-Year Limited Condenser Warranty.
The listing gives air handler, outdoor condenser and pre-charged 25 ft quick connect line in the box.
Who it's for, and who should skip it
Good fit if
- Rooms of about 700-1,000 sq ft
- DIY installs
Look elsewhere if
- Primary heat in cold climates
- Spaces much larger than 1,000 sq ft
- Line runs longer than the included pre-charged set
Pros and cons
Pros
- 22.5 SEER2
- 18,000 BTU heating stated
- No refrigerant handling to install
- Quiet indoor head (19 dB)
Cons
- Low-temperature heating not stated
Limitations to weigh
- Capacity and efficiency are the maker's ratings; real output depends on the install, the line length and the weather.
- Heat pumps lose heating capacity as it gets colder; size for your climate with the BTU calculator.
- The federal 25C tax credit ended for systems installed after 2025; check your utility for current rebates.
Specifications
Every figure below comes from the source shown in brackets. Where the maker doesn't state something, we say so instead of estimating.
| Price | $2,609 | Retailer |
|---|---|---|
| Model number | DIY-18-HP-WM-230D25-O | Retailer |
| Cooling capacity (maker) | 18000 BTU | Retailer |
| Heating capacity (maker) | 18000 BTU | Retailer |
| SEER2 (maker) | 22.5 | Retailer |
| HSPF2 (maker) | 11.5 | Retailer |
| Room size (maker) | 550-800 sq ft | Retailer |
| Voltage | 230V | Retailer |
| Refrigerant | R-454B | Retailer |
| Noise (seller) | 19 dB | Retailer |
| Warranty | Eligible for MRCOOL Care Program, 5-Year Limited Parts Warranty, 7-Year Limited Condenser Warranty | Retailer |
Alternatives worth comparing
More ductless mini-splits we cover
- MRCOOL DIY 5th Gen 36,000 BTU 230V $3,469
- Senville Floor Console 12,000 BTU 230V
- Rellytech 9,000 BTU 115V Mini-Split
- Rellytech 12,000 BTU 115V Mini-Split
All ductless mini-splits, compared in one table · Every MRCOOL product we cover
Final verdict
The pick if you want to install it yourself. Check that 18,000 BTU fits your room with the BTU calculator before you buy.
Where to buy
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