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Bosch / Climate 5000 Gen 4

Bosch Climate 5000 G4 18k Regular R-454B Mini-Split

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

Stepping up to 18,000 BTU, this Climate 5000 is Bosch's cold-climate head for larger rooms - a big living room, open area, or master suite. Its selling point is the same as the smaller cold-climate models: strong, steady heat deep into winter, so a large space stays warm without a second heat source.

It runs current R-454B refrigerant and is ENERGY STAR certified and cold-climate rated. As with the rest of the line it is a dealer install, and the value of Bosch's warranty and service network only grows as the equipment gets bigger and pricier.

1 zoneProfessional installCurrent

Refrigerant generation

R-454B - current-generation refrigerant

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Error Codes
Bosch Climate 5000 Gen 4 R-454B wall-mounted indoor unit (BMS500-AAU012-1AHWXD) for Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD)

Image: Hydrowest Products

Data completeness: 92%
Last sourced
Jul 26, 2026

SplitAtlas score

8.9 / 10

Methodology
Cooling efficiencyTop quartile

(23.5 SEER2) among 18k systems

Heating efficiencyTop quartile

(10.8 HSPF2) among 18k systems

Cold-weather performanceBelow average

(5F certified capacity: 71.1% of the 47F rating; -13 F heating floor) among 18k systems

NoiseTop 10%

(20 dBA indoor min / 58 dBA outdoor) among 18k systems

WarrantyTop quartile

(10 yr parts / 10 yr compressor) across the catalogue

Feature setTop quartile

(6 verified features) across the catalogue

Documentation & partsBottom quartile

(6 manuals) across the catalogue

Not evaluated

  • Installation accessibility — not applicable (professional install)N/A

    professional install - DIY-accessibility not applicable

  • Price-to-value — not evaluatedN/A

    This is a professionally installed, quote-only system, so we can't score its price. Get an installed quote to compare real cost.

    Get a quote

Key ratings

Rated cooling

18,000BTU/h[2]

Rated heating

18,000BTU/h[2]

Buyer review snapshot

Best for / skip if

Best for

  • High-efficiency shortlists; SEER2 is 23.5.

Install difficulty

Professional install
  • Electrical: 230V; MCA 18 A; breaker/fuse 20 A.
  • Line set: connection type not sourced; precharged 24.6 ft; max 98.4 ft.

Alternatives

Availability and price context

This system needs a professional install, so its real price is an installed quote that depends on your home. We don't link to a listing for this exact model; get installation quotes to price it.

Source date

Model data sourced
Jul 26, 2026
Page reviewed
Jul 22, 2026
Source-backed records
5
Newest source retrieved
Jul 26, 2026

Warranty tiers

Base
10 yr parts / 10 yr compressor - limited residential warranty terms

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

Review methodology

Model context

Structured ratings
Certification: ENERGY STAR certified and AHRI cold-climate designated. Refrigerant: current low-GWP R-454B. Minimum heating ambient: -13 F.

Strengths

  • Strong, steady winter heat for a large room - it holds most of its 18k output at 17F and stays substantial well into sub-freezing.
  • Good heating-season efficiency for this capacity, so a big space does not punish your winter bills.
  • Bosch's warranty and dealer network are a real advantage over value brands as capacities - and potential repair costs - climb.

Weaknesses

  • Cooling efficiency sits a notch below the smaller heads, if summer performance is your main concern.
  • Dealer-installed premium equipment, so total cost runs higher than budget alternatives.

Climate suitability

Minimum heating ambient
-13 F[1]
Certified heating at 5F
12,800 BTU/h[2]
Rated heating at 17F
15,000 BTU/h[2]
Rated heating at 47F
18,000 BTU/h[2]

Specifications

Show
Manufacturer
Bosch
Brand
Bosch
Product line
Climate 5000 Gen 4
Model number
BMS500-AAU018-1AHWXD indoor / BMS500-AAS018-1CSXRD outdoor
Indoor unit model
BMS500-AAU018-1AHWXD
Outdoor unit model
BMS500-AAS018-1CSXRD
Number of zones
1
Max indoor units
not published
Rated cooling capacity
18,000 BTU/h[2]
Rated heating capacity
18,000 BTU/h[2]
Voltage
230 V[1]
MCA
18 A[1]
Maximum fuse or breaker size
20 A[1]
Breaker needed
not published
SEER2
23.5 SEER2[2]
EER2
12.7 EER2[2]
HSPF2 (Region 4)
10.8 HSPF2[2]
HSPF2 (Region 5)
not published
COP
not published
COP at 47F
3.5 COP[1]
COP at 5F
2.1 COP[2]
Minimum outdoor heating temperature
-13 F[1]
Minimum outdoor cooling temperature
-13 F[1]
Maximum outdoor temperature
122 F[1]
Indoor noise range
20-49 dB(A)[1]
Outdoor noise rating
58 dBA[1]
Indoor weight
27.34 lb[1]
Outdoor weight
92.59 lb[1]
Refrigerant
R-454B[2]
Refrigerant charge
47.97 oz[1]
Manufacturer coverage
not published
Line-set size
1/4 in liquid / 1/2 in suction
Included line-set length
Bosch submittals publish field piping sizes and precharged refrigerant length, but do not specify an included line set for these professional-install systems.
Maximum line-set length
98.4 ft[1]
Max line set per indoor
not published
Maximum elevation difference
65.6 ft[1]
Max height between indoor units
not published
Wi-Fi support
not published
Energy Star status
ENERGY STAR certified[4]
AHRI certification number
215223302[2]
Warranty
Base: 10 yr parts / 10 yr compressor (limited residential warranty terms). Score uses Base.. 10-year compressor / 10-year parts limited residential warranty; terms and field-installed component limits apply.
Install path
Professional install
Retail price
Installed quote only
Available retailers
not published
Manual links
AHRI public directory record 215223302, ENERGY STAR exact check 215223302, Climate 5000 Ductless System Mini-Split Heat Pump (R-454B Version), Bosch Climate 5000 ductless mini-split submittal sheet directory, BMS500-AAU018-1AHWXD & BMS500-AAS018-1CSXRD Bosch Climate 5000 Gen 4 R-454B submittal
Specification sheet
not published
Last sourced date
Jul 26, 2026

Electrical requirements

Show
Voltage
230 V[1]
Voltage range
208/230V[1]
Phase
1[1]
Frequency
60 Hz[1]
MCA
18 A[1]
Breaker needed
not published
Maximum breaker size
20 A[1]
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
not published
Precharged length
24.6 ft[1]
Included line-set length
Bosch submittals publish field piping sizes and precharged refrigerant length, but do not specify an included line set for these professional-install systems.
Maximum line-set length
98.4 ft[1]
Max line set per indoor
not published
Max height between indoor units
not published
Indoor dimensions
38.0 x 9.8 x 12.56 in[1]
Outdoor dimensions
35.04 x 13.46 x 26.50 in[1]
Indoor weight
27.34 lb[1]
Outdoor weight
92.59 lb[1]
Drain size
not published

Related systems and guides

Frequently asked questions

Can I install the Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD) myself, or do I need a pro?
Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD) is built for professional installation: the line set must be flared, evacuated, and charged, which requires EPA-certified refrigerant handling. Installing it outside the manufacturer's requirements can void the warranty, so budget for a qualified HVAC installer.
Will the Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD) keep heating in a cold winter?
The AHRI/ENERGY STAR certification lists 12,800 BTU/h of heating capacity at 5F. Rated heating operation extends down to -13 F. Certified heating efficiency is 10.8 HSPF2. Match those numbers against your climate's design temperature - in cold regions, output at 5F matters far more than the nameplate capacity measured at 47F.
What electrical circuit does the Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD) need?
Published electrical requirements: 230 V 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.
How far can the outdoor unit be from the indoor head?
The published maximum line-set length is 98.4 ft. The outdoor unit's factory charge covers up to 24.6 ft of line; longer runs need added refrigerant. Measure the planned routing before ordering.
What warranty does the Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Regular (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXRD) carry?
The manufacturer publishes these warranty tiers: Base: 10 yr parts / 10 yr compressor (limited residential warranty terms). 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. Bosch Thermotechnology Corp.: BMS500-AAU018-1AHWXD & BMS500-AAS018-1CSXRD Bosch Climate 5000 Gen 4 submittalSourced - manufacturer technical document

    Covers Frequency, electrical_spec.indoor_mca_amps, Maximum breaker size, Maximum fuse size, Minimum circuit ampacity, Phase and more

  2. AHRI Directory: AHRI public directory record 215223302Sourced - AHRI directory

    Covers AHRI certification number, Rated cooling capacity, COP at 5F, EER2, Rated heating capacity, HSPF2 (Region 4) and more

  3. Air-Conditioning, Heating, and Refrigeration Institute: AHRI Appendix M1 public detail for BMS500-AAS018-1CSXRD / BMS500-AAU018-1AHWXDSourced - AHRI directory

    Covers performance_spec.cold_climate_designation, system.lifecycle_status

  4. ENERGY STAR Certified Air-Source Heat Pumps Directory: ENERGY STAR record 3554558 for BMS500-AAS018-1CSXRD / BMS500-AAU018-1AHWXDSourced - Energy Star listing

    Covers Energy Star status

  5. Bosch Thermotechnology Corp.: Climate 5000 Ductless System Mini-Split Heat Pump (R-454B Version) manufacturer pageSourced - manufacturer product page

    Covers Legacy compressor warranty value, Legacy warranty value, Base compressor warranty, Base warranty conditions, Base parts warranty, Warranty notes

Last updated

Jul 22, 2026