Bosch / Climate 5000 Gen 4
Bosch Climate 5000 G4 9k Max R-454B Mini-Split
This is Bosch's cold-climate flagship in its smallest size - a 9,000 BTU head built for one room in a place with real winters. Most mini-splits fade as the temperature drops, but this one holds a flat 12,000 BTU of heat from a mild 47F all the way down to 17F and barely eases to 11,500 BTU at 5F, so the room stays warm on the nights a heat pump usually struggles.
It is also the single most efficient unit in the whole Climate 5000 range at 27.4 SEER2, so those winter gains don't come at the cost of summer bills, and it runs on low-GWP R-454B refrigerant with ENERGY STAR certification. The trade-off is simple: this is premium, Bosch-dealer-installed equipment, and in a mild climate you'd be paying for cold-weather muscle you will never use.
Refrigerant generation
R-454B - current-generation refrigerant
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Image: Hydrowest Products
- Last sourced
- Jul 26, 2026
SplitAtlas score
9.0 / 10
(27.4 SEER2) among <=9k systems
(12.5 HSPF2) among <=9k systems
(5F certified capacity: 95.8% of the 47F rating; -22 F heating floor) among <=9k systems
(19.5 dBA indoor min / 56 dBA outdoor) among <=9k 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
The one to get for a bedroom or small living space in a genuinely cold region, where you want a heat pump you can actually rely on at 5F instead of falling back on a furnace.
Buyer review snapshot
Best for / skip if
Best for
- Top efficiency shortlists; SEER2 is 27.4.
Install difficulty
- Electrical: 230V; MCA 15 A; breaker/fuse 15 A.
- Line set: connection type not sourced; precharged 24.6 ft; max 82 ft.
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
- 6
- 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
- The most efficient head Bosch makes here at 27.4 SEER2 - low running cost in both seasons.
- Heat barely moves as it gets cold: a flat 12,000 BTU from 47F to 17F and still 11,500 BTU at 5F, so no backup heater is needed.
- Future-proof R-454B refrigerant, ENERGY STAR certified and cold-climate rated, backed by Bosch's warranty.
Weaknesses
- Flagship cold-climate engineering means a premium price, and it is dealer-installed only - not a DIY kit.
- Overkill anywhere winters are mild, where that flat cold-weather curve buys you little.
Climate suitability
- Minimum heating ambient
- -22 F[1]
- Certified heating at 5F
- 11,500 BTU/h[3]
- Rated heating at 17F
- 12,000 BTU/h[3]
- Rated heating at 47F
- 12,000 BTU/h[3]
Specifications
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- Manufacturer
- Bosch
- Brand
- Bosch
- Product line
- Climate 5000 Gen 4
- Model number
- BMS500-AAU009-1AHWXD indoor / BMS500-AAS009-1CSXHD outdoor
- Indoor unit model
- BMS500-AAU009-1AHWXD
- Outdoor unit model
- BMS500-AAS009-1CSXHD
- Number of zones
- 1
- Max indoor units
- not published
- Rated cooling capacity
- 9,000 BTU/h[3]
- Rated heating capacity
- 12,000 BTU/h[3]
- Voltage
- 230 V[1]
- MCA
- 15 A[1]
- Maximum fuse or breaker size
- 15 A[1]
- Breaker needed
- not published
- SEER2
- 27.4 SEER2[3]
- EER2
- 15.4 EER2[3]
- HSPF2 (Region 4)
- 12.5 HSPF2[3]
- HSPF2 (Region 5)
- not published
- COP
- not published
- COP at 47F
- 3.76 COP[1]
- COP at 5F
- 1.8 COP[3]
- Minimum outdoor heating temperature
- -22 F[1]
- Minimum outdoor cooling temperature
- -22 F[1]
- Maximum outdoor temperature
- 122 F[1]
- Indoor noise range
- 19.5-38 dB(A)[1]
- Outdoor noise rating
- 56 dBA[1]
- Indoor weight
- 23.37 lb[1]
- Outdoor weight
- 72.75 lb[1]
- Refrigerant
- R-454B[3]
- Refrigerant charge
- 35.27 oz[1]
- Manufacturer coverage
- not published
- Line-set size
- 1/4 in liquid / 3/8 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
- 82 ft[1]
- Max line set per indoor
- not published
- Maximum elevation difference
- 49.2 ft[1]
- Max height between indoor units
- not published
- Wi-Fi support
- not supported[2]
- Energy Star status
- ENERGY STAR certified[5]
- AHRI certification number
- 215223278[3]
- 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 215223278, ENERGY STAR exact check 215223278, Climate 5000 Ductless System Mini-Split Heat Pump (R-454B Version), Bosch Climate 5000 ductless mini-split submittal sheet directory, BMS500-AAU009-1AHWXD & BMS500-AAS009-1CSXHD 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
- 3/8 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
- 82 ft[1]
- Max line set per indoor
- not published
- Max height between indoor units
- not published
- Indoor dimensions
- 33.74 x 9.09 x 11.81 in[1]
- Outdoor dimensions
- 31.69 x 12.99 x 21.81 in[1]
- Indoor weight
- 23.37 lb[1]
- Outdoor weight
- 72.75 lb[1]
- Drain size
- not published
Related systems and guides
- More Bosch systems
- Bosch Climate 5000 A B Legacy 9k Regular R-410A Mini-Split
Previous generation
- Bosch Climate 5000 G4 9k Regular R-454B Mini-Split
- Blueridge XS6 Max Efficiency 9k R-454B 208/230V Mini-Split
- Carrier Comfort 22 9k R-454B 115V 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 9,000 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
- Your mini split is showing a refrigerant leak code
- Mini split short cycling
- Line sets
- Line-set covers
Frequently asked questions
- Can I install the Bosch Climate 5000 Gen 4 R-454B 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD) myself, or do I need a pro?
- Bosch Climate 5000 Gen 4 R-454B 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD) 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 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD) keep heating in a cold winter?
- The AHRI/ENERGY STAR certification lists 11,500 BTU/h of heating capacity at 5F. Rated heating operation extends down to -22 F. Certified heating efficiency is 12.5 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 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD) need?
- Published electrical requirements: 230 V voltage, 15 A minimum circuit ampacity, and 15 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 82 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 9,000 BTU Max Performance (BMS500-AAU009-1AHWXD / BMS500-AAS009-1CSXHD) 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-AAU009-1AHWXD & BMS500-AAS009-1CSXHD 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
- Bosch Thermotechnology Corp.: Air-to-Air R-454B Heat Pump Systems FAQSourced - manufacturer product page
Covers Wi-Fi support
- AHRI Directory: AHRI public directory record 215223278Sourced - 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-AAS009-1CSXHD / BMS500-AAU009-1AHWXDSourced - AHRI directory
Covers performance_spec.cold_climate_designation, system.lifecycle_status
- ENERGY STAR Certified Air-Source Heat Pumps Directory: ENERGY STAR record 3554534 for BMS500-AAS009-1CSXHD / BMS500-AAU009-1AHWXDSourced - 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