SplitAtlas

MRCOOL / DIY 5th Generation

MRCOOL DIY 5th Gen 18k 230V Mini-Split

Certified capacity
18,000 BTU/h[1]
SEER2
22.5 SEER2[1]
Heating floor
-13 F[2]
Voltage
208/230V[1]
Install path
DIY install

The 18k is where the DIY line steps up to 230V and larger spaces: same pre-charged quick-connect install path, sized for open living areas and two-car garages, with rated heating down to -13F.

1 zoneDIY installCurrent

Refrigerant generation

R-454B - current-generation refrigerant

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Error Codes
MRCOOL DIY 5th Gen 18k single-zone mini-split system with indoor wall unit, outdoor condenser, and line set

Image: HVACDirect

Data completeness: 88%
Last sourced
Aug 17, 2026

SplitAtlas score

8.9 / 10

Methodology
Cooling efficiencyAbove average

(22.5 SEER2) among 18k systems

Heating efficiencyTop quartile

(11.5 HSPF2) among 18k systems

Cold-weather performanceBelow average

(-13 F heating floor) among 18k systems

NoiseTop 10%

(19 dBA indoor min / 58.5 dBA outdoor) among 18k systems

WarrantyBelow average

(5 yr parts / 7 yr compressor) across the catalogue

Installation accessibilityAbove average

(DIY-marketed; 25 ft precharged; 25 ft included line set) across the catalogue

Documentation & partsTop 10%

(2 manuals; spec sheet; 50 error-code rows; parts channel) across the catalogue

Key ratings

Rated cooling

18,000BTU/h[1]

Rated heating

18,000BTU/h[1]

Best-fit use cases

Open living areas, large additions, and garage workshops where the owner wants to self-install and can have an electrician run the 230V circuit.

Where this system ranks

Buyer review snapshot

Best for / skip if

Best for

  • High-efficiency shortlists; SEER2 is 22.5.

Install difficulty

DIY install path, electrical work likely
  • Electrical: 208/230V; MCA 18 A; breaker/fuse 20 A.
  • Line set: Quick-connect line connections; precharged 25 ft; included 25 ft.

Alternatives

Availability and price context

  • Last seen at HVACDirect on Jul 27, 2026: $2,909.00. Open the listing for today's price.

Source date

Model data sourced
Aug 17, 2026
Page reviewed
Jul 18, 2026
Source-backed records
4
Newest source retrieved
Aug 17, 2026

Warranty tiers

Base
5 yr parts / 7 yr compressor - standard coverage

The score uses Base. Additional published terms are shown for reference and not counted in the score.

Review methodology

Strengths

  • The largest spaces a true DIY install path currently reaches comfortably - no vacuum pump or gauges for a standard install.
  • Rated heating to -13F suits three-season garages and additions.
  • Complete public documentation, consistent with the DIY line.

Weaknesses

  • Needs a 230V dedicated circuit - the "no electrician" part of the DIY story does not apply at this size.
  • The AURA 18k undercuts it on price while certifying a deeper -22F heating floor - though the MRCOOL's certified efficiency (SEER2 22.5 / HSPF2 11.5) is actually the higher of the two at this size.
  • Same paid-program warranty caveat as the rest of the line.

Climate suitability

Minimum heating ambient
-13 F[2]
Certified heating at 5F
not published
Rated heating at 17F
not published
Rated heating at 47F
not published

Specifications

Show
Manufacturer
MRCOOL
Brand
MRCOOL
Product line
DIY 5th Generation
Model number
DIY-18-HP-WMAH-230D25-O indoor / DIY-18-HP-C-230D25-O outdoor
Indoor unit model
DIY-18-HP-WMAH-230D25-O
Outdoor unit model
DIY-18-HP-C-230D25-O
Number of zones
1
Max indoor units
not published
Rated cooling capacity
18,000 BTU/h[1]
Rated heating capacity
18,000 BTU/h[1]
Voltage
208/230V[1]
MCA
18 A[1]
Maximum fuse or breaker size
20 A[1]
Breaker needed
not published
SEER2
22.5 SEER2[1]
EER2
13.7 EER2[1]
HSPF2 (Region 4)
11.5 HSPF2[1]
HSPF2 (Region 5)
8.5 HSPF2[1]
COP
not published
COP at 47F
not published
COP at 5F
not published
Minimum outdoor heating temperature
-13 F[2]
Minimum outdoor cooling temperature
not published
Maximum outdoor temperature
not published
Indoor noise range
54.5/44.5/40.5/30.5/19.0 dB(A)[1]
Outdoor noise rating
58.5 dBA[1]
Indoor weight
35.49 lb[2]
Outdoor weight
93.48 lb[2]
Refrigerant
R-454B[1]
Refrigerant charge
44.8 oz[1]
Manufacturer coverage
800 sq ft[1]
Line-set size
1/4 in liquid / 1/2 in suction
Included line-set length
25 ft[1]
Maximum line-set length
not published
Max line set per indoor
not published
Maximum elevation difference
not published
Max height between indoor units
not published
Wi-Fi support
not published
Energy Star status
ENERGY STAR certified[2]
AHRI certification number
216032545[2]
Warranty
Base: 5 yr parts / 7 yr compressor (standard coverage). Score uses Base.. 5-year parts plus 7-year compressor standard; lifetime via paid Care Kit only.
Install path
DIY install
Retail price
last seen at HVACDirect on Jul 27, 2026: $2,909.00
Available retailers
HVACDirect
Manual links
MRCOOL DIY Series Single-Zone Mini-Split System Installation & Owner's Manual, MRCOOL R454B DIY-5 submittal
Specification sheet
MRCOOL R454B DIY-5 submittal
Last sourced date
Aug 17, 2026

Retail purchase context

Some retailer links may earn us a commission at no extra cost; paid relationships never change scores or recommendations. Affiliate disclosure

Paid link

Check price at HVACDirect

Reference-only price

Last seen at HVACDirect on Jul 27, 2026: $2,909

Parts and filters

Fits MRCOOL DIY 5th Gen 18,000 BTU (230V). Part numbers and fit notes identify compatibility only; no manufacturer endorsement is implied.

filter-washable

Washable air filter

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
Filter care
Washable. Clean and reuse. MRCOOL does not publish a calendar cleaning interval for the primary filter. Replace if damaged or no longer cleanable.
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. The indoor filter is a cleanable service item. MRCOOL does not publish an orderable model-specific filter SKU in the service manual; source replacements through the installer, place of purchase, or MRCOOL authorized parts support at https://support.mrcool.com/hc/en-us/articles/28733842948884-Where-Can-I-Purchase-Parts-for-MRCOOL-Systems.
Source
MRCOOL DIY 5th Gen Service Manual, 4.5 Error Diagnosis Without Error Code - Remote Maintenance, page p. 46 (Dirty air filter ... Clean or replace)

remote-control

Remote control

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. MRCOOL does not publish an OEM part number for the remote; its authorized Mass HVAC store sells a 4th/5th Gen replacement.
Source
MRCOOL DIY 5th Gen Service Manual, 4.5 Remote Maintenance, page p. 46 (Replace the remote control)

smart-thermostat

MRCOOL Smart Wi-Fi Mini Stat

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
OEM part number
MST05
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. MRCOOL publishes MST05 for its mini-splits. HVACDirect lists MST04, a different part, so no HVACDirect link is shown. MRCOOL's authorized store also offers the MTSK02 Mini-Stat.
Source
MRCOOL Mini-Stats, MRCOOL Mini Stats, page article (MST05)

quick-connect-line-set

25 ft Quick Connect precharged line set - 1/4 x 1/2

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
OEM part number
DIY25-1412-O
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. Use this 1/4 x 1/2 R-454B Quick Connect line set for compatible MRCOOL DIY 18k indoor heads. HVACDirect was verified as a live exact-part page on 2026-08-01.
Source
MRCOOL 5th Gen R-454B DIY Line Set 1/4 - 1/2, DIY 5th Gen 9k, 12k & 18k, page article (DIY25-1412-O)

Some retailer links may earn us a commission at no extra cost; paid relationships never change scores or recommendations. Affiliate disclosure

Paid link

Check price at HVACDirect

display-board

Display board (service part)

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. The service manual identifies the display board as a replaceable diagnostic item, but does not publish a model-specific orderable SKU. Use model and serial through MRCOOL support or an authorized parts distributor.
Source
MRCOOL DIY 5th Gen Service Manual, 4.2 Error Display (Indoor Unit), page p. 36 (If the unit responds, the display board requires replacement.)

indoor-pcb

Indoor control board / PCB (service part)

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. The service manual identifies the indoor PCB as the replacement path when the unit does not respond to the remote, but does not publish a model-specific orderable SKU. Use model and serial through MRCOOL support or an authorized parts distributor.
Source
MRCOOL DIY 5th Gen Service Manual, 4.2 Error Display (Indoor Unit), page p. 36 (If the unit does not respond to the remote, the indoor PCB requires replacement.)

louver-motor

Louver stepping motor (service part)

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. The service manual calls for replacing the stepping motor when the horizontal louver will not move, but does not publish a model-specific orderable SKU. Use model and serial through MRCOOL support or an authorized parts distributor.
Source
MRCOOL DIY 5th Gen Service Manual, 4.5 Field Maintenance, page p. 50 (Replace the stepping motor)

air-cleaning-accessory

MRCOOL Cool Care kit (MMCK01)

Fits
MRCOOL DIY 5th Gen 18,000 BTU (230V)
OEM part number
MMCK01
Fit note
Fits DIY-18-HP-WMAH-230D25-O / DIY-18-HP-C-230D25-O. MRCOOL lists the Cool Care kit (MMCK01) for this model; each six-month kit includes a replacement air-freshening filter. This accessory is separate from the washable primary filter.
Source
MMCK01 COOL Care Program Kit, Compatibility, page article (Each shipment includes ... a fresh air filter. Compatibility: MRCOOL DIY Mini Split System.)
Find this model's filterReplacement Parts & Filters

Electrical requirements

Show
Voltage
not published
Voltage range
208/230V[1]
Phase
1[1]
Frequency
60 Hz[1]
MCA
18 A[1]
Breaker needed
not published
Maximum breaker size
not published
Maximum fuse size
20 A[1]
Maximum cooling current
not published
Maximum heating current
not published
Manufacturer wire notes
not published

Installation considerations

Show
Liquid line
1/4 in[1]
Suction line
1/2 in[1]
Line connection type
Quick-connect line connections[3]
Precharged length
25 ft[1]
Included line-set length
25 ft[1]
Maximum line-set length
not published
Max line set per indoor
not published
Max height between indoor units
not published
Indoor dimensions
42.52 x 8.90 x 13.19 in[1]
Outdoor dimensions
35.04 x 13.46 x 26.50 in[1]
Indoor weight
35.49 lb[2]
Outdoor weight
93.48 lb[2]
Drain size
not published

Comparable models

MRCOOL DIY vs DIY Hyper Heat (18,000 BTU)

Side-by-side comparison

MRCOOL DIY vs Senville AURA (18,000 BTU) - The Garage & Great-Room Size

Side-by-side comparison

Related systems and guides

Frequently asked questions

Can I install the MRCOOL DIY 5th Gen 18,000 BTU (230V) myself, or do I need a pro?
MRCOOL DIY 5th Gen 18,000 BTU (230V) is sold as a DIY-installable system with an included 25 ft line set, so a standard install needs no vacuum pump or gauges. EPA's Section 608 guidance says connecting pre-charged lines still requires technician certification. The electrical circuit is the part that is not DIY: plan on a licensed electrician for the dedicated circuit, and check whether your local permit office requires a permit for the install.
Will the MRCOOL DIY 5th Gen 18,000 BTU (230V) keep heating in a cold winter?
Rated heating operation extends down to -13 F. Certified heating efficiency is 11.5 HSPF2. Match that published heating floor against your climate's design temperature - below the low-ambient rating, output can fall off or the system can pause to protect itself.
What electrical circuit does the MRCOOL DIY 5th Gen 18,000 BTU (230V) need?
Published electrical requirements: 208/230V voltage, 18 A minimum circuit ampacity, and 20 A maximum breaker or fuse sizing. Confirm the final circuit against the unit nameplate and local code with a licensed electrician.
What warranty does the MRCOOL DIY 5th Gen 18,000 BTU (230V) carry?
The manufacturer publishes these warranty tiers: Base: 5 yr parts / 7 yr compressor (standard coverage). Score uses Base.. Registration requirements and proof of qualified installation commonly affect coverage, so read the warranty terms before install day.

Data sources

Show
  1. MRCOOL: MRCOOL R454B DIY-5 submittalSourced - manufacturer technical document

    Covers Frequency, Maximum fuse size, Minimum circuit ampacity, Phase, Voltage range, Manufacturer coverage and more

  2. HVACDirect: HVACDirect product page DIY-18-HP-WM-230D25-OSourced - authorized distributor

    Covers Indoor weight, Outdoor weight, AHRI certification number, Energy Star status, Minimum outdoor heating temperature

  3. MRCOOL: MRCOOL DIY Series Single-Zone Mini-Split System Installation & Owner's ManualSourced - manufacturer technical document

    Covers Line connection type

  4. HVACDirect: HVACDirect product page DIY-18-HP-WM-230D25-OSourced - authorized distributor

    Covers Retail price

Last updated

Jul 18, 2026