Bosch / Climate 5000 Gen 4
Bosch Climate 5000 G4 18k Max R-454B Mini-Split
This 18k head is the purest expression of the Max Performance idea: its heating output is dead-flat at 18,000 BTU whether it is 47F, 17F, or a brutal 5F outside. Capacity simply does not sag as the cold deepens, which is exactly what you want when the heat pump is your primary source of warmth.
That single-mindedness costs a little on the cooling side - its 21.4 SEER2 sits near the low end of Bosch's R-454B range - but its heating-season efficiency (HSPF2 11) is strong. It is premium, dealer-installed Bosch equipment, ENERGY STAR certified and cold-climate rated.
Refrigerant generation
R-454B - current-generation refrigerant
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Image: Hydrowest Products
- Last sourced
- Jul 26, 2026
SplitAtlas score
9.0 / 10
(21.4 SEER2) among 18k systems
(11.0 HSPF2) among 18k systems
(5F certified capacity: 100% of the 47F rating; -22 F heating floor) among 18k systems
(19.5 dBA indoor min / 59 dBA outdoor) among 18k systems
(10 yr parts / 10 yr compressor) across the catalogue
(6 verified features) across the catalogue
(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.
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Key ratings
Best-fit use cases
Ideal for a large room or open area in a harsh-winter region where holding full 18k heat at 5F matters more than squeezing out summer efficiency.
Buyer review snapshot
Install difficulty
- Electrical: 230V; MCA 19 A; breaker/fuse 20 A.
- Line set: connection type not sourced; precharged 24.6 ft; max 98.4 ft.
Alternatives
- Blueridge XS6 Max Efficiency 18,000 BTU R-454B 208/230V (BXS6A18WM0 / BXS6A18UC0)
9.2 score / 18k / SEER2 25.6 / -22 F heating floor / 230V
Exact destination at Alpine Home Air: $2,359.00, checked Jul 24, 2026
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.
Model context
- Structured ratings
- Certification: ENERGY STAR certified and AHRI cold-climate designated. Refrigerant: current low-GWP R-454B. Minimum heating ambient: -22 F.
Strengths
- Dead-flat 18,000 BTU of heat at 47F, 17F, and 5F - full rated warmth even in deep cold.
- Strong heating-season efficiency (HSPF2 11) for a head this size.
- Current R-454B refrigerant, ENERGY STAR certified, with Bosch warranty and dealer support.
Weaknesses
- Cooling efficiency of 21.4 SEER2 is near the low end of Bosch's R-454B lineup - this tier prioritizes heat.
- Flagship, dealer-installed pricing that is hard to justify where winters are mild.
Climate suitability
- Minimum heating ambient
- -22 F[1]
- Certified heating at 5F
- 18,000 BTU/h[2]
- Rated heating at 17F
- 18,000 BTU/h[2]
- Rated heating at 47F
- 18,000 BTU/h[2]
Specifications
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- Manufacturer
- Bosch
- Brand
- Bosch
- Product line
- Climate 5000 Gen 4
- Model number
- BMS500-AAU018-1AHWXD indoor / BMS500-AAS018-1CSXHD outdoor
- Indoor unit model
- BMS500-AAU018-1AHWXD
- Outdoor unit model
- BMS500-AAS018-1CSXHD
- 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
- 19 A[1]
- Maximum fuse or breaker size
- 20 A[1]
- Breaker needed
- not published
- SEER2
- 21.4 SEER2[2]
- EER2
- 12.5 EER2[2]
- HSPF2 (Region 4)
- 11 HSPF2[2]
- HSPF2 (Region 5)
- not published
- COP
- not published
- COP at 47F
- 3.26 COP[1]
- COP at 5F
- 1.92 COP[2]
- Minimum outdoor heating temperature
- -22 F[1]
- Minimum outdoor cooling temperature
- -22 F[1]
- Maximum outdoor temperature
- 122 F[1]
- Indoor noise range
- 19.5-49.5 dB(A)[1]
- Outdoor noise rating
- 59 dBA[1]
- Indoor weight
- 27.34 lb[1]
- Outdoor weight
- 99.87 lb[1]
- Refrigerant
- R-454B[2]
- Refrigerant charge
- 55.38 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
- 215223286[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 215223286, ENERGY STAR exact check 215223286, Climate 5000 Ductless System Mini-Split Heat Pump (R-454B Version), Bosch Climate 5000 ductless mini-split submittal sheet directory, BMS500-AAU018-1AHWXD & BMS500-AAS018-1CSXHD Bosch Climate 5000 Gen 4 R-454B submittal
- Specification sheet
- not published
- Last sourced date
- Jul 26, 2026
Installation considerations
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- 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 26.5 in[1]
- Indoor weight
- 27.34 lb[1]
- Outdoor weight
- 99.87 lb[1]
- Drain size
- not published
Related systems and guides
- More Bosch systems
- Bosch Climate 5000 G4 18k Regular R-454B 208/230V 3-Zone Mini-Split
- Bosch Climate 5000 G4 18k Regular R-454B Mini-Split
- Blueridge XS6 Max Efficiency 18k R-454B 208/230V Mini-Split
- Carrier Comfort 22 18k R-454B 208/230V Mini-Split
- Guide library
- Mini split buying guide
- Single-zone vs multi-zone mini splits
- Troubleshooting
- Do mini splits work in cold weather?
- Bosch mini split review: is Bosch any good?
- The best 18,000 BTU mini splits of 2026
- The best cold-climate mini splits of 2026
- The best mini splits for heating of 2026
- Mini split heating capacity in the cold: what your unit actually delivers at 5F
- The mini split defrost cycle, explained
- The best DIY mini splits of 2026
- What "DIY mini split" actually means
- How to install a mini split (DIY overview)
- Mini split not heating
- Mini split indoor unit freezing up
- Mini split remote not working
- One room won't heat or cool on a multi-zone mini split
- Mini split Wi-Fi not connecting
- Line sets
- Line-set covers
Frequently asked questions
- Can I install the Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Max Performance (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXHD) myself, or do I need a pro?
- Bosch Climate 5000 Gen 4 R-454B 18,000 BTU Max Performance (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXHD) 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 Max Performance (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXHD) keep heating in a cold winter?
- The AHRI/ENERGY STAR certification lists 18,000 BTU/h of heating capacity at 5F. Rated heating operation extends down to -22 F. Certified heating efficiency is 11 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 Max Performance (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXHD) need?
- Published electrical requirements: 230 V voltage, 19 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 Max Performance (BMS500-AAU018-1AHWXD / BMS500-AAS018-1CSXHD) 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
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- Bosch Thermotechnology Corp.: BMS500-AAU018-1AHWXD & BMS500-AAS018-1CSXHD 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
- AHRI Directory: AHRI public directory record 215223286Sourced - AHRI directory
Covers AHRI certification number, Rated cooling capacity, COP at 5F, EER2, Rated heating capacity, HSPF2 (Region 4) and more
- Air-Conditioning, Heating, and Refrigeration Institute: AHRI Appendix M1 public detail for BMS500-AAS018-1CSXHD / BMS500-AAU018-1AHWXDSourced - AHRI directory
Covers performance_spec.cold_climate_designation, system.lifecycle_status
- ENERGY STAR Certified Air-Source Heat Pumps Directory: ENERGY STAR record 3554542 for BMS500-AAS018-1CSXHD / BMS500-AAU018-1AHWXDSourced - Energy Star listing
Covers Energy Star status
- 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