How loud is the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?

54 dB(A) indoors, about as loud as a dishwasher.

How energy-efficient is the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?

Its efficiency rating is SEER2 22.5.

What size room does the MRCOOL DIY 5th Gen 18,000 BTU Mini Split cool?

It is rated to cool a room up to 800 sq ft (18,000 BTU · 5.3 kW).

Do I need a professional to install the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?

Partly. MRCOOL sells it as a do-it-yourself kit: the line set comes pre-charged with quick-connect fittings, so there is no vacuum pump or refrigerant charging on site, and you can mount the units and route the lines yourself. But under EPA Section 608 connecting refrigerant lines is certified-technician work, so plan on a certified technician for that connection. Usually needs permission.

Does the MRCOOL DIY 5th Gen 18,000 BTU Mini Split heat as well as cool?

Yes. It also heats, rated 18,000 BTU of heating output.

How cold can it get outside before the MRCOOL DIY 5th Gen 18,000 BTU Mini Split stops heating?

Its retailer's specification for this exact configuration rates it to keep heating down to -13°F outdoors. That is its operating limit, not its full output: a heat pump delivers less heat as it gets colder, so size it for your coldest days.

Single splitSEER2 22.5 Heats too

MRCOOL · Model DIY-18-HP-WM-230D25-O

DIY 5th Gen 18,000 BTU Mini Split

Name: MRCOOL DIY 5th Gen 18,000 BTU Mini Split
Brand: MRCOOL
Price: 2609 USD
Availability: InStock

A wall-mounted split air conditioner rated at 18,000 BTU for rooms up to 800 sq ft. It heats in winter too.

$2,609

Live price at Sylvane

Price checked Sep 30, 2026

Buy at Sylvane In stock

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Price history at Sylvane

Lowest since Jul 25, 2026:$2,609on Sep 27, 2026

Currently the lowest price we have tracked at Sylvane since Jul 25, 2026down from $2,909 on Sep 26, 2026

Based on 53 prices we have recorded since Jul 25, 2026, not a market average.

Will it cool your room?

Room size (assumed)800 sq ft ≈ 74.3 m²

Fits a 74.3 m² room

This unit's cooling matches a 800 sq ft room. Set your room size to check the fit for your space.

Running cost

Mini-splits are rated on SEER2, a seasonal scale, not the ENERGY STAR annual-kWh figure this dollar estimate is built from, so there is no comparable figure to show here. A blank is missing data, not a worse result: a mini-split is often the more efficient choice.

At a glance

Best for larger open-plan rooms.

Cooling

5.3 kW

Size

Average

Noise

54 dB

Audible

Install: DIY kit, certified refrigerant hookupPermission: Usually needs permission

Performance

Cooling capacity: 18,000 BTU · 5.3 kW
Heating capacity: 18,000 BTU
Heats down to: -13°F outdoors
Room coverage: up to 800 sq ft
Energy Star: Not published
SEER2: 22.5
EER2: 13.7
Annual energy (cooling): Not published

Noise, size & features

Model number: DIY-18-HP-WM-230D25-O
Indoor noise: 54 dB(A)about as loud as a dishwasher
Outdoor noise: Not published
Indoor unit: 42.5 x 13.2 x 8.9 in
Outdoor unit: 35 x 26.5 x 13.5 in (W x H x D)
Refrigerant: R-454B
Wi-Fi / app: Not published
Outdoor unit needed: Yes
Warranty: Eligible for MRCOOL Care Program, 5-Year Limited Parts Warranty, 7-Year Limited Condenser Warranty

EER2, SEER2, warranty, heating capacity, refrigerant, heating limit and outdoor unit size are from Sylvane's published specifications for this exact configuration, checked Sep 26, 2026.

What is good

Its SEER2 22.5 is more efficient than 50 of the 63 other mini-splits we list with a published SEER2.
Uses R-454B (GWP 466), the low-GWP class new US residential equipment moved to.

What to watch

At $2,609 it costs more than 16 of the 17 other 15,000-18,000 BTU mini-splits we list with a live price.

Installation & the rules that apply

This is a single split. This is where regulation bites. Under EPA Section 608 the refrigerant circuit may only be opened by a certified technician, and the EPA is explicit that this includes connecting or disconnecting the pre-charged line sets sold with "DIY" mini-split kits. No federal law stops you doing the mounting, bracketing and line routing yourself, but handling the refrigerant without certification voids the warranty and is a violation. Most US jurisdictions also require permits for a new outdoor unit: typically mechanical or building for the wall penetration and mount, plus electrical for the dedicated 240 V circuit and disconnect. An HOA nearly always has to approve exterior equipment in advance, and local noise ordinances can cap how loud the condenser may be at the property line. This varies by city and county, so confirm with your building department before buying hardware.

Installation

DIY kit, certified refrigerant hookup

Refrigerant

R-454B

GeneralRenters: get written landlord consent firstReviewed June 2026Often blocks install

United StatesUS: EPA Section 608 certified technician for refrigerantReviewed June 2026Often blocks install

ArizonaArizona: municipal mechanical permit for AC replacementReviewed June 2026Permit required

CaliforniaCalifornia: Title 24 permit and HERS verificationReviewed June 2026Permit required

FloridaFlorida: hurricane wind-load anchoring of outdoor unitsReviewed June 2026Permit required

See full rules by region

Common questions about the MRCOOL DIY 5th Gen 18,000 BTU Mini Split

How loud is the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?: 54 dB(A) indoors, about as loud as a dishwasher.
How energy-efficient is the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?: Its efficiency rating is SEER2 22.5.
What size room does the MRCOOL DIY 5th Gen 18,000 BTU Mini Split cool?: It is rated to cool a room up to 800 sq ft (18,000 BTU · 5.3 kW).
Do I need a professional to install the MRCOOL DIY 5th Gen 18,000 BTU Mini Split?: Partly. MRCOOL sells it as a do-it-yourself kit: the line set comes pre-charged with quick-connect fittings, so there is no vacuum pump or refrigerant charging on site, and you can mount the units and route the lines yourself. But under EPA Section 608 connecting refrigerant lines is certified-technician work, so plan on a certified technician for that connection. Usually needs permission.
Does the MRCOOL DIY 5th Gen 18,000 BTU Mini Split heat as well as cool?: Yes. It also heats, rated 18,000 BTU of heating output.
How cold can it get outside before the MRCOOL DIY 5th Gen 18,000 BTU Mini Split stops heating?: Its retailer's specification for this exact configuration rates it to keep heating down to -13°F outdoors. That is its operating limit, not its full output: a heat pump delivers less heat as it gets colder, so size it for your coldest days.

Is a split even the right type?

Compare splits against the other types on price, noise, efficiency and install.

Mini-split vs window Mini-split vs portable

Buying guides for a single split like this

The questions buyers ask, answered from live prices and real specs. See where a single split like this fits.

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