Home / Comparisons / 3-ton central heat pumps
FUJITSU AIRSTAGE CENTAURI XLTH R32 and GREE FLEXX ULTRA R32, figure by figure
Two 3-ton R-32 central heat pumps, each with its outdoor unit and air handler, ENERGY STAR cold climate certified and offered by AirGreen. Their certified seasonal efficiencies are a few tenths apart. Their maximum capacity in cold weather is not. This page shows both, temperature by temperature.
CENTAURI XLTH R32 · 36,000 BTU
AMUH36KUAS / AOUH36KUAH1 · AHRI 217895717
See the product page
FLEXX ULTRA R32 · 3 tons
FXU36HP230V1R32AH / FXU36HP230V1R32AO · AHRI 215213330
See the product pageWhat the electricity costs, in dollars, winter and summer
AirGreen estimate for the same 36,000 BTU/h (3-ton) house in Montréal, on Hydro-Québec Rate D, taxes included. Winter comes down to one figure, the Region V HSPF2: 8.2 for the CENTAURI XLTH, 7.6 for the FLEXX ULTRA. For the same heat delivered, the FLEXX ULTRA draws about 8% more electricity. In summer the SEER2 gap (18.3 and 18.0) stays under 2%. The certificates give 36,000 and 34,000 BTU/h of cooling at 35 °C: the calculation uses the common nominal size, 36,000 BTU/h, for both, with electric baseboards as the reference.
How this amount is calculated
- Heat to supply over the winter. A house whose heat loss reaches 36,000 BTU/h ( kW) at −23.1 °C, the Montréal design temperature: kW × 24 h × 4,167 degree-days ÷ (18 − (−23.1)) = kWh of heat for round-the-clock heating, all winter. Heating degree-days (18 °C base) and design temperature: Natural Resources Canada, HOT2000 climate data, Montréal Intl station. With fewer hours a day (“Heating” slider), the heat is reduced in the same proportion, for the heat pump as for the baseboards: this simplification ignores the recovery after a temperature setback.
- Heating electricity. Heat pump: heat × 3.412 ÷ HSPF2 Region V, the AHRI certificate value published by NEEP. Region V is the coldest in the standard, and its calculation includes the electric backup heat expected when the heat pump is no longer enough. Electric baseboards: 1 kWh of electricity for 1 kWh of heat.
- Cooling electricity. 36,000 BTU/h ÷ SEER2 × hours a day × 60 days ÷ 1,000: the method of Hydro-Québec’s air-conditioning calculator, with the seasonal SEER2 efficiency from the AHRI certificate. The number of hours is a scenario, adjustable above from 1 to 24 h. At 24 h, the calculation assumes rated capacity all day long: that is a ceiling, since a variable-speed unit slows down once the room reaches its set temperature.
- Price. Hydro-Québec Rate D in effect April 1, 2026: 7.065¢ per kWh up to 40 kWh a day, 11.142¢ beyond; the average price, 9.104¢, is the one Hydro-Québec’s calculators use. GST and QST included. Grid access charges, the same with or without a heat pump, are not counted.
AirGreen method v1.1, November 9, 2026. An estimate is a way to compare units under the same conditions. The actual bill depends on the house, its insulation, the settings and how it is used; this amount is not a promise.
Twin houses, two systems, the same cold outside
The first house is heated by the CENTAURI XLTH, the second by the FLEXX ULTRA. Pick an outdoor temperature: each unit shows the maximum heating capacity published at that temperature, and warm air moves through the ducts at the pace of that capacity. The vertical line on each gauge marks 36,000 BTU/h, the 3-ton rated size.
A diagram, not an installation plan: the units are to scale with each other (heights published by each manufacturer), the house and ducts are illustrative. The speed of the warm air in the drawing follows the published capacity; it does not represent a measured airflow or air temperature.
Nearly equal efficiencies, a different reserve
Seasonal efficiencies measure how much heat or cooling comes out per kilowatt-hour over a whole season. Maximum capacity says how much the unit can deliver at a given moment. On these two units, the first is alike; the second is not.
Certified seasonal efficiencies
Same scale for both units on each row. Relative gap of 2 to 8%.
Certified maximum capacity
At the three temperatures where NEEP measures both units. Vertical line: 36,000 BTU/h.
The modulation range at 8.3 °C
A variable-speed heat pump slows down in mild weather. Bar: from certified minimum to certified maximum capacity; yellow tick: the rated value.
Below −15 °C: −26.1 °C on one side, −30 °C on the other
NEEP measures both systems at the same temperatures down to −15 °C. Lower down, each has its own coldest point: −26.1 °C for the CENTAURI XLTH, −30 °C for the FLEXX ULTRA. Each figure is placed at its own temperature, with its source; nothing is calculated between two points.
What each manufacturer writes, line by line
FUJITSU AIRSTAGE submittal sheet 36KUAH1M and Centauri brochure FG8161D; GREE FLEXX ULTRA R32 Canadian brochure and GREE submittal sheet FXU36. Nothing is added: a feature missing from a card is missing from the documents reviewed.
CENTAURI XLTH: heating stated down to −26 °C, no low-temperature cutoff; built-in heated base pan; automatic defrost.
FLEXX ULTRA: heating stated down to −30 °C; base pan with electric heater; so-called smart defrost and preheating; compressor heater.
CENTAURI XLTH: down to −21 °C (−5 °F) outside.
FLEXX ULTRA: down to −15 °C (5 °F) outside.
CENTAURI XLTH: Auto and four speeds (high, medium, low, quiet); external static pressure up to 0.8 in. w.c.; multi-position (upflow, left, right; downflow with kit).
FLEXX ULTRA: five speeds; up to 1.0 in. w.c.; multi-position air handler.
CENTAURI XLTH: third-party 24 V thermostat through the UTY-TTRXZ1 interface; wired controls, UTY-LBTUM remote and IR receiver kit and UTY-TFSXJ4 Wi-Fi adapter (AIRSTAGE Mobile app), all optional; BACnet and Modbus.
FLEXX ULTRA: conventional 24 V AC thermostat; RS485 communication; Ultra Heat and dual fuel compatible, per GREE.
CENTAURI XLTH: optional electric heater kits (UTZ-EU series), on a dedicated circuit; emergency heat configurable through an output terminal.
FLEXX ULTRA: optional 5, 8 or 10 kW electric element (Canadian brochure); the US sheet names 6, 9 and 12 kW kits.
CENTAURI XLTH: leak sensor built into the air handler.
FLEXX ULTRA: not mentioned in the brochure or sheet reviewed; the nameplate and the installation manual are authoritative.
CENTAURI XLTH: Economy mode, weekly and 24-hour timer, sleep mode, auto restart; input and output terminals for a humidifier, HRV, backup heat.
FLEXX ULTRA: restart after a power outage, low-voltage start, self-diagnosis.
CENTAURI XLTH: inverter compressor; Blue Fin-treated outdoor coil.
FLEXX ULTRA: GREE G20 inverter compressor, two cylinders, two stages.
CENTAURI XLTH: 20 × 20 in. filter base available as an option (86ET0001) for 30 to 48k models.
FLEXX ULTRA: published airflows are measured with the factory filter; size not stated in the documents reviewed.
How loud each one is, per its manufacturer
FUJITSU AIRSTAGE publishes a level for each fan speed of the AMUH36KUAS air handler. GREE publishes a single value for the FXU36 air handler and one for the outdoor unit. Both give sound pressure in dB(A).
How to read these figures. dB(A) measures a noise level as the ear perceives it: the lower the figure, the quieter the unit. Each point is a value published by the manufacturer. An air handler usually sits in a basement or a closet: what you hear in the rooms also depends on the ducts and their insulation.
Why this is not a ranking. FUJITSU AIRSTAGE measures in its own anechoic chamber. GREE publishes neither the distance, the speed nor the conditions of its measurement. A gap of a few dB(A) can come from the method as much as from the unit.
Air handler
Cooling, published values
Outdoor unit, outside
Published value
GREE publishes one value per unit, FUJITSU AIRSTAGE one per speed: two methods, read them separately, not as a ranking.
In the basement, outside and in the piping
All four units at the same scale
Net heights and weights per the manufacturers. Photos: FUJITSU AIRSTAGE submittal sheet 36KUAH1M; GREE (FLEXX ULTRA series images on greecomfort.com). The three-quarter view of the FUJITSU AIRSTAGE air handler also shows its side.
Piping length between the two units
FLEXX ULTRA precharge: 25 ft per the GREE Canadian brochure (the US submittal sheet says 31 ft). The installer always confirms with the installation manual and the nameplate.
| Installation | CENTAURI XLTH | FLEXX ULTRA |
|---|---|---|
| Maximum piping length | 246 ft | 164 ftCanadian brochure table and submittal sheet; the brochure cover says 131 ft. |
| Minimum piping length | 17 ft | 10 ft |
| Precharged length | 98 ft | 25 ftCanadian brochure; US submittal sheet: 31 ft. |
| Refrigerant added beyond the precharged length | 0.43 oz/ft | 0.323 oz/ft |
| Maximum height difference | 98 ft | 98 ft |
| Liquid – gas diameters | 3/8 – 5/8 in | 3/8 – 3/4 in |
| Outdoor unit W × H × D, weight | 37 × 39 5/16 × 12 5/8 in, 159 lb | 39 × 37 13/16 × 14 9/16 in, 187.4 lb |
| Indoor unit W × H × D, weight | 21 × 48 × 21 in, 137 lb | 21 1/4 × 48 3/16 × 21 1/4 in, 163.1 lb |
| Indoor airflow, rated or high speed | 1,200 CFM (high) | 1,000 CFM (rated) |
| Maximum external static pressure | 0.8 in. w.c. | 1.0 in. w.c. |
| Electrical protectionPer the manufacturer | Breaker max. 35 A (MCA 33.9 A) | Outdoor: MOCP 30 A (MCA 27.7 A); air handler: MOCP 15 A (MCA 5.3 A) |
| Dehumidification | 3.82 L/h | Not published by the manufacturer. |
| Stated heating / cooling range | −26 to 24 °C / −21 to 50 °C | −30 to 24 °C / −15 to 54 °C |
Sources: FUJITSU AIRSTAGE submittal sheet 36KUAH1M (version 20260123A); GREE FLEXX ULTRA R32 Canadian brochure (BRO0125) and GREE submittal sheet FXU36. The GREE brochure swaps the “indoor unit” and “outdoor unit” headers in its table and labels its ranges in °C while the values are in °F: the page follows the model numbers and converts.
What people ask about these two central systems
Their seasonal efficiencies are nearly equal: where is the difference?
The AHRI certificates give a SEER2 of 18.3 and 18.0 and an HSPF2 Region IV of 10.2 and 10.0. The clearest difference is maximum capacity in cold weather: 41,000 and 34,000 BTU/h at −15 °C, per NEEP.
Why does the page use 36,000 BTU/h if the FLEXX ULTRA is certified at 34,000?
Both are sold as 3-ton systems. The FLEXX ULTRA certificate gives 34,000 BTU/h of cooling at 35 °C, the CENTAURI XLTH certificate 36,000. The estimated cost uses the common nominal size, 36,000 BTU/h, for both; certified capacities are shown as they are everywhere else.
Why is one measured at −26.1 °C and the other at −30 °C?
Each manufacturer has its system measured at the bottom of its stated range: −15 °F (−26.1 °C) for FUJITSU AIRSTAGE, −22 °F (−30 °C) for GREE. The 32,000 BTU/h of the CENTAURI XLTH at −26.1 °C and the 20,400 BTU/h of the FLEXX ULTRA at −30 °C therefore do not compare directly.
What happens below −26 °C with the CENTAURI XLTH?
Per the FUJITSU AIRSTAGE submittal sheet, the system has no low-temperature cutoff and keeps running below its stated range, depending on conditions. The manufacturer specifies that capacity is not measured outside that range, so the page shows no figure below −26.1 °C for this system.
Is a thermostat supplied?
Both manufacturers' documents describe control by a 24 V thermostat; neither lists a thermostat among the supplied parts. With FUJITSU AIRSTAGE, the thermostat interface, the remote and Wi-Fi are optional accessories. What an AirGreen quote includes is confirmed in the quote.
Are they eligible for rebates?
Both are certified ENERGY STAR cold climate per NEEP and the ENERGY STAR directory. Eligibility depends on the official list in effect on the purchase date; this page promises no amount.
All AHRI and NEEP values
| Certified value | CENTAURI XLTH | FLEXX ULTRA |
|---|---|---|
| Cooling | ||
| Rated capacity at 35 °C | 36,000 BTU/h | 34,000 BTU/h |
| SEER2 | 18.3 | 18.0 |
| EER2 | 11.4 | 11.2 |
| Heating, same conditions | ||
| HSPF2 Region IV / V | 10.2 / 8.2 | 10.0 / 7.6 |
| 8.3 °C: min. / rated / max.BTU/h | 9,200 / 38,000 / 43,000 | 11,200 / 34,000 / 34,400 |
| 8.3 °C: COP min. / rated / max. | 3.80 / 3.89 / 3.28 | 4.62 / 3.20 / 3.20 |
| −8.3 °C: min. / rated / max.BTU/h | 8,300 / 25,200 / 41,600 | 9,200 / 32,600 / 32,600 |
| −8.3 °C: COP min. / rated / max. | 3.86 / 2.90 / 2.25 | 2.64 / 2.50 / 2.47 |
| −15 °C: min. / rated / max.BTU/h | 7,900 / 41,000 / 41,000 | 16,000 / 34,000 / 34,000 |
| −15 °C: COP min. / rated / max. | 3.86 / 1.98 / 1.98 | 2.29 / 2.00 / 2.00 |
| Coldest point — different temperatures, not highlighted | ||
| Test temperature | −26.1 °C (−15 °F) | −30 °C (−22 °F) |
| Capacity min. / max. | 6,000 / 32,000 BTU/h | 15,000 / 20,400 BTU/h |
| COP at maximum capacity | 1.82 | 1.31 |
| Listings and refrigerant | ||
| ENERGY STAR / cold climate (NEEP) | Yes / Yes | Yes / Yes |
| ENERGY STAR directory, markets listed | United States, Canada | United States, Canada |
| AHRI certificate · NEEP record | 217895717 · 306746 | 215213330 · 392095 |
| RefrigerantGWP per the IPCC (AR4); ASHRAE 34 class | R-32 · GWP 675 · A2L | R-32 · GWP 675 · A2L |
higher marks the higher value of a given measure, under the same conditions. It is not a recommendation. Capacities and COPs by point are not highlighted: the order changes depending on the point read. The GREE brochure prints a SEER2 of 16.5, an EER2 of 11.4 and an HSPF2 of 9.5 for this model; the GREE submittal sheet says 18.0, 12.0 and 10.0. This page follows AHRI certificate 215213330.
Both are on the AirGreen website.
To choose for your house, talk it over with our team: bring the heated area, the condition of your ducts, the planned outdoor location and your current heating.
Where each figure comes from
Data checked on November 9, 2026. Performance: AHRI certificates and the NEEP database. Dimensions, sound, piping and features: per the manufacturer. When a source contradicts the AHRI certificate, the certificate prevails.
Trademarks. FUJITSU AIRSTAGE, CENTAURI, GREE and FLEXX ULTRA are trademarks of their respective owners. Logos are used only to identify the products compared. AirGreen is a dealer for both brands; this page is not produced, sponsored or endorsed by the manufacturers. The FUJITSU AIRSTAGE system is also sold under the name GENERAL AIRSTAGE.
Photos: AirGreen and the manufacturers, for identification.
Does a figure look wrong to you? Write to us : every reported figure is checked again.