Home / Comparisons / 3-ton central heat pumps
GREE FLEXX ULTRA R32 and MIDEA EVOX G3, from the season to extreme cold
Two 3-ton central heat pumps, certified ENERGY STAR cold climate and offered by AirGreen. Over the season, their AHRI certificates give the same SEER2 and the same HSPF2 in Region IV. The gaps show up elsewhere: in Region V, the coldest, and at the certified −30 °C point.
What the electricity costs, in dollars, winter and summer
AirGreen estimate for the same 36,000 BTU/h house in Montréal, at Hydro-Québec Rate D, taxes included. Both heat pumps are calculated exactly the same way, with the same method as on all our comparison pages; only their certified efficiencies change. Electric baseboards serve as the reference. The FLEXX ULTRA is certified at 34,000 BTU/h in cooling and the EVOX G3 at 36,000: the calculation uses their common nominal size, 3 tons.
How this amount is calculated
- Heat needed over the winter. A house whose heat loss reaches 36,000 BTU/h ( kW) at −23.1 °C, Montréal’s 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 (base 18 °C) 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 and the baseboards alike: a simplification that ignores the recovery after a setback.
- Electricity for heating. 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 planned for when the heat pump is no longer enough. Electric baseboards: 1 kWh of electricity for 1 kWh of heat.
- Electricity for cooling. 36,000 BTU/h ÷ SEER2 × hours per day × 60 days ÷ 1,000: the method of Hydro-Québec’s air-conditioning calculator, with the SEER2 seasonal 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: that is a maximum, since a variable-speed unit slows down once the room is at the right 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. The network access fee, the same with or without a heat pump, is not counted.
AirGreen method v1.1, November 9, 2026. An estimate is for comparing units under the same conditions. The actual bill depends on the house, insulation, settings and use; this amount is not a promise.
Two identical rings, two that pull apart
Each ring is a seasonal value from the AHRI certificate, published by NEEP. Outer ring: GREE FLEXX ULTRA R32. Inner ring: MIDEA EVOX G3. For the same measure, both rings are drawn on the same scale.
Four test temperatures, the same for both
NEEP publishes both units at the same four temperatures, down to −30 °C. Pick a temperature: each column fills up to the certified maximum capacity; the yellow line marks the smallest certified capacity at the same point.
At −30 °C, NEEP publishes only a minimum and a maximum capacity; there is no rated value at that point. The percentage compares the maximum capacity at −30 °C with each unit’s certified rated capacity at 8.3 °C (34,000 and 37,000 BTU/h).
Below −15 °C: every published figure, at its exact temperature
NEEP certifies both units at −15 °C and at −30 °C. In between, GREE publishes a maximum-capacity table every 5 °F (the page uses three of them, plus its −15 °C point); MIDEA publishes none for this combination. Each figure is placed at its temperature, with its source. Nothing is calculated between two points.
What each manufacturer writes
GREE FLEXX ULTRA R32 brochures and submittal sheet; MIDEA EVOX G3 submittal sheet, leaflet and installation manual. Each row repeats what the manufacturer writes.
FLEXX ULTRA: GREE G20, twin-cylinder, two-stage inverter (English brochure).
EVOX G3: twin-cylinder rotary EKPQ420D1UMUA (submittal sheet); “M-Powevi” vapour injection in extreme cold (leaflet).
FLEXX ULTRA: RS485 communication or universal 24 V control; compatible with a conventional 24 V thermostat.
EVOX G3: 485 or 24 V mode; sub-1 GHz wireless modules; MIDEA communicating thermostat; SmartHome app.
FLEXX ULTRA: 5-speed centrifugal fan; 1,000 CFM; external static pressure up to 1.0 in w.c.
EVOX G3: “2.0” constant airflow; 5 published speeds, up to 1,236 CFM; 0 to 1.0 in w.c.
FLEXX ULTRA: 6, 9 or 12 kW kits (submittal sheet); the French brochure states 5, 8 and 10 kW.
EVOX G3: three-stage kit, up to 25 kW (leaflet).
FLEXX ULTRA: heating stated down to −30 °C; smart defrost and preheating.
EVOX G3: continuous operation stated down to −30 °C; adjustable defrost algorithm (installation manual).
FLEXX ULTRA: low-voltage startup, restart after a power failure, self-diagnosis; cooling from −15 to 54 °C outdoors.
EVOX G3: iCheck self-diagnosis; cooling from −30 to 50 °C outdoors.
The EVOX G3 also pairs with other MIDEA indoor units; this page covers the certified MAUSE-H36B-2A / MO1SE-H36B-2A combination only.
How loud each one is, per its manufacturer
GREE publishes a single value for the FLEXX ULTRA indoor unit. MIDEA publishes five for the EVOX G3, one per speed. Neither states its measurement method.
How to read these numbers. dB(A) measures noise level as the ear perceives it: the lower the number, the quieter the unit. Each point is a value published by the manufacturer; for the EVOX G3, one per fan speed.
Why this is not a ranking. Neither GREE nor MIDEA publishes the distance, speed or measurement conditions for these values. Different or unknown method: not comparable.
Indoor unit, in the basement or a closet
Published values
Outdoor unit, outside
Published value
Measurements taken by each manufacturer with its own method: read them separately, not as a ranking.
Outdoors, in the basement, and the piping in between
Dark band: factory-precharged length. Light band: up to the maximum published length, with refrigerant added. FLEXX ULTRA: 31 ft precharged per the GREE submittal sheet of May 2025 (both brochures print 25 ft), 0.323 oz per foot beyond, 164 ft maximum. EVOX G3: 25 ft precharged, 0.7 oz per foot beyond (submittal sheet), 246 ft maximum (installation manual).
Outdoor units to scale
Width to scale; the photos are taken in perspective. Both manufacturers ask for at least 24 in in front of the unit for service. MIDEA also asks for it to be installed at least 11.8 in above the highest expected snow level.
Indoor units, front view
Diagram to scale (width and height), from published dimensions. Depth: 21 1/4 in and 21 1/2 in. Weight: 163.1 lb and 149 lb.
| Installation | FLEXX ULTRA | EVOX G3 |
|---|---|---|
| Maximum piping length | 164 ft | 246 ftMIDEA installation manual, rev. 5, October 23, 2025. |
| Precharged length | 31 ftGREE submittal sheet, May 2025; the brochures state 25 ft. | 25 ft |
| Maximum height difference | 98 ft | 98.4 ft |
| Liquid – gas line diameters | 3/8 – 3/4 in | 3/8 – 3/4 in |
| Outdoor unit W × H × D, weight | 39 × 37 13/16 × 14 9/16 in, 187.4 lb | 38 9/16 × 38 3/8 × 16 3/8 in, 204 lb |
| Indoor unit, weightL × H × P | 21 1/4 × 48 3/16 × 21 1/4 in, 163.1 lb | 17 1/2 × 58 1/8 × 21 1/2 in, 149 lb |
| Electrical protectionPer the manufacturer | Outdoor: MCA 27.7 A, MOCP 30 A; indoor: MCA 5.3 A, MOCP 15 A | Outdoor: MCA 29 A, MOP 30 A; indoor: MCA 6 A, MOP 15 A (208/230 V) |
| Indoor fan | 5 speeds, 1,000 CFM published | 5 speeds, 971 to 1,236 CFM |
| Factory refrigerant charge | 102.3 oz of R-32 | 127 oz of R-454B |
| Stated heating / cooling range | −30 to 24 °C / −15 to 54 °C | −30 to 24 °C / −30 to 50 °C |
Sources: GREE submittal sheet GREE_FXU36_230V_R32_SUB_05162025 and English brochure GREE_FLEXX_ULTRA_R32_032725; MIDEA MAUSE-H36B-2A / MO1SE-H36B-2A submittal sheet and EVOX Extreme Heat installation manual. The GREE outdoor unit dimensions follow its specification table; the drawing on the same sheet shows a different depth (29 3/4 in), with no explanation.
What people ask about these two systems
They have the same SEER2: is there any difference in summer?
The AHRI certificates give 18.0 for both. EER2, measured at 35 °C outdoors, is 11.2 for the FLEXX ULTRA and 12.0 for the EVOX G3. Certified cooling capacity is 34,000 and 36,000 BTU/h.
Why is HSPF2 equal in Region IV and different in Region V?
The standard calculates HSPF2 for several climates. In Region IV, both score 10.0. In Region V, which is colder, the FLEXX ULTRA scores 7.6 and the EVOX G3 8.2. The cost estimated above uses Region V, closer to a Montréal winter.
What do they deliver at −30 °C?
Per NEEP, 20,400 BTU/h maximum for the FLEXX ULTRA (COP 1.31) and 27,600 BTU/h for the EVOX G3 (COP 1.56). Both are tested at the same temperature, −30 °C (−22 °F).
The GREE brochure says SEER2 16.5: why does the page say 18.0?
The French GREE brochure (code BRO0125) prints 16.5 for the 3-ton, and the English brochure 18.0. AHRI certificate 215213330, carried by NEEP, states 18.0. When sources disagree, this page follows the certificate.
Which one is quieter?
GREE publishes 51 dB(A) for the indoor unit; MIDEA publishes 33 to 48 dB(A) depending on speed. Outdoors: 61 and 63 dB(A). Neither publishes its measurement method: these numbers cannot be used to rank the units.
Can a furnace be kept as backup?
GREE states that the FLEXX ULTRA works with dual-fuel backup (“Dual Fuel”); MIDEA offers the EVOX G3 as an ADD-ON version, on a coil set on an existing furnace. Those are other combinations, with other AHRI certificates than the ones on this page.
Are they eligible for rebates?
Eligibility depends on the official list in force on the date of purchase. This page promises no amount; the current list is checked at quotation time.
All AHRI and NEEP values
| Certified value | FLEXX ULTRA | EVOX G3 |
|---|---|---|
| Cooling | ||
| Rated capacity at 35 °C | 34,000 BTU/h | 36,000 BTU/h |
| SEER2 | 18.0 | 18.0 |
| EER2 | 11.2 | 12.0 |
| Heating, same conditions | ||
| HSPF2 Region IV | 10.0 | 10.0 |
| HSPF2 Region V | 7.6 | 8.2 |
| 8.3 °C: min. / rated / max.BTU/h | 11,200 / 34,000 / 34,400 | 11,400 / 37,000 / 47,000 |
| 8.3 °C: COP min. / rated / max. | 4.62 / 3.20 / 3.20 | 4.45 / 3.50 / 3.27 |
| −8.3 °C: min. / rated / max.BTU/h | 9,200 / 32,600 / 32,600 | 11,000 / 33,000 / 41,500 |
| −8.3 °C: COP min. / rated / max. | 2.64 / 2.50 / 2.47 | 2.58 / 2.50 / 2.21 |
| −15 °C: min. / rated / max.BTU/h | 16,000 / 34,000 / 34,000 | 8,900 / 37,400 / 37,400 |
| −15 °C: COP min. / rated / max. | 2.29 / 2.00 / 2.00 | 2.16 / 1.90 / 1.90 |
| Coldest point — same temperature for both | ||
| Test temperature | −30 °C (−22 °F) | −30 °C (−22 °F) |
| Min. / max. capacity | 15,000 / 20,400 BTU/h | 4,700 / 27,600 BTU/h |
| COP at maximum capacity | 1.31 | 1.56 |
| Listings and refrigerant | ||
| ENERGY STAR / cold climate (NEEP) | Yes / Yes | Yes / Yes |
| AHRI certificate · NEEP record | 215213330 · 392095 | 215471343 · 387396 |
| RefrigerantGWP per the IPCC (AR4); ASHRAE 34 class | R-32 · GWP 675 · A2L | R-454B · GWP 466 · A2L |
higher marks the higher value of the same measure, under the same conditions. It is not a recommendation. Capacities and COPs at each point are not highlighted: the order changes depending on the point. At the coldest point, both are tested at −30 °C; those values are compared in “The cold room”.
Both are on the AirGreen website.
To choose for your home, talk it over with our team: bring the heated floor area, the condition of your ducts and your current heating.
Where every figure comes from
Data verified 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. GREE, FLEXX ULTRA, MIDEA and EVOX 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.
Photos: AirGreen and manufacturers, for identification.
Does a figure look wrong to you? Write to us: every reported figure is checked again.