GOODMAN//Wall units//Series 21
Goodman Series 21 wall heat pump: heat published down to -25 °C
Three sizes, 12,000, 18,000 and 24,000 BTU/h, on R-410A and 208-230 V. For each one, GOODMAN prints the maximum heating capacity at -8.3, -15 and -25 °C. This page puts them side by side, with the share of heat left once the cold sets in.
The question this page answersHow much heat does a Goodman 21 still deliver at -8.3, -15 and -25 °C?
The three Goodman 21 units in our store
Each product page leads to a quote request. Not every size reaches the "21 SEER" in the titles: GOODMAN publishes 20.8 and 20.5 for the 18,000 and the 24,000.
Tool//Cold-weather output
How much heat is left at -8.3, -15 and -25 °C
Pick a size and an outdoor temperature. The bars give the maximum capacity GOODMAN publishes at -8.3, -15 and -25 °C, and the rated heat at 8.3 °C; the "Share of rated heat" box says how much is left.
Goodman 21, 18,000 BTU/h at -15 °C (5 °F)
MSH183E21MCAA + MSH183E21AXAA
- Published maximum capacity
- 11,500 BTU/h
- Share of rated heat
- 64%of 18,000 BTU/h, AirGreen calculation
Rated heat at 8.3 °CPublished maximum capacityRated capacity at 17 °F (06-21 revision)
Within the published range. At -15 °C (5 °F), the 18,000 keeps at most 64% of its rated heat; GOODMAN still publishes a point at -25 °C.
See the 18,000 BTU/h product pagePublished maximum capacity: what the unit can deliver at the test point, not an output it holds continuously. The grey 8.3 °C bar is the rated heat, the base of the share shown. The teal mark on the -8.3 °C bar is the rated capacity at 17 °F from the 06-21 revision, a different measure. GOODMAN publishes no value below -25 °C.
Series 21//Winter in Montreal
Series 21 against a Montreal winter
The capacities GOODMAN publishes (source 1), set against the 1991-2020 normals and extremes at Montréal-Trudeau (source 6).
At -25 °C, 41 to 48% is left
At -25 °C, GOODMAN publishes a maximum capacity of 5,800, 7,400 and 11,000 BTU/h for the 12,000, the 18,000 and the 24,000 (source 1, p. 6), that is 48, 41 and 44% of their rated heat (AirGreen calculation).
January and February at Montréal-Trudeau
At January's normal daily minimum, -13.5 °C (1991-2020 normals, source 6), each size sits between its published points of -8.3 and -15 °C: 9,130 to 8,000, 12,900 to 11,500 and 17,510 to 15,500 BTU/h at most (AirGreen's reading between two published points).
The lowest minimum observed in February from 1991 to 2020 is -30.3 °C, on February 6, 1993: 5.3 °C below the last published point (AirGreen calculation).
GOODMAN//Specifications
The three sizes, line by line
Values from the 03-21 brochure unless stated otherwise. Highlighted cells mark where the 24,000 stands apart.
GOODMAN data, sources 1 to 3
| Published value | 12,000 | 18,000 | 24,000 |
|---|---|---|---|
| Outdoor unit | MSH123E21MCAA | MSH183E21MCAA | MSH243E21MCAA |
| Rated cooling | 12,000 BTU/h | 18,000 BTU/h | 24,000 BTU/h |
| SEER | 21.5 | 20.8 | 20.5 |
| EER | 13.0 | 13.0 | 12.5 |
| Rated heating at 8.3 °C (47 °F) | 12,000 BTU/h | 18,000 BTU/h | 25,000 BTU/h |
| COP at 8.3 °C | 3.24 | 3.36 | 3.16 |
| HSPF region IV / region V | 9.8 / 7.7 | 10.0 / 8.0 | 10.0 / 8.3 |
| Published maximum at -15 °C (5 °F) | 8,000 BTU/h | 11,500 BTU/h | 15,500 BTU/h |
| Refrigerant lines, liquid / gas | 1/4 in and 1/2 in | 1/4 in and 1/2 in | 3/8 in and 5/8 in |
| Maximum line length / maximum lift | 82 / 33 ft | 98 / 66 ft | 164 / 82 ft |
| Outdoor unit, W × D × H | 31.50 × 13.11 × 21.81 in | 33.27 × 14.29 × 27.64 in | 37.24 × 16.14 × 31.89 in |
| Outdoor unit sound (06-21 revision) | 55 dB(A) | 60 dB(A) | 61 dB(A) |
| Minimum circuit ampacity / maximum fuse | 12 / 15 A | 15 / 20 A | 18 / 25 A |
Where the documents disagree: rated heating of the 24,000, 25,000 BTU/h (2021 brochures) rather than 24,000 (2018); SEER of the 18,000, 20.8 (03-21 and 2018) rather than 21 (06-21); outdoor sound, the 06-21 revision, the most recent; outdoor unit of the 24,000, the 2021 brochures rather than 40.55 × 16.54 × 31.89 in (2018). Rule: two documents that agree win, otherwise the most recent. The precharge (15 to 25 ft depending on the document) is not quoted.
Compare//Same capacity
Series 21 or Series 19, at 24,000 BTU/h
Same size, same brochure, two series. Pricing comes with the estimate; here is what GOODMAN publishes for each.
GOODMAN data, source 1, p. 5 and 6
| At 24,000 BTU/h | Series 21 | Series 19 |
|---|---|---|
| SEER | 20.5 | 17.0 |
| HSPF region IV / region V | 10.0 / 8.3 | 9.5 / 8.0 |
| Rated heating at 8.3 °C | 25,000 BTU/h | 24,000 BTU/h |
| COP at 8.3 °C | 3.16 | 3.20 |
| Heating published down to | -25 °C | -15 °C |
| Published maximum at -15 °C | 15,500 BTU/h | not published |
| Maximum line length | 164 ft | 98 ft |
| Maximum lift | 82 ft | 66 ft |
| Outdoor unit, W × D × H | 37.24 × 16.14 × 31.89 in | 33.3 × 14.3 × 27.7 in |
| Minimum circuit ampacity / maximum fuse | 18 / 25 A | 20 / 25 A |
GOODMAN publishes no Series 19 capacity below 8.3 °C, hence the "not published" on the "maximum at -15 °C" line. See the Series 19 page.
Did you know//GOODMAN documents
Three Series 21 details you rarely see
A heated base pan and crankcase from the factory
In its 2018 French document, GOODMAN lists a factory-installed base-pan heater and a factory-installed crankcase heater for the Series 21 outdoor unit, and notes that both come only on Series 17 and 21.
Source 3, p. 9The 9,000 is sold for multi-zone only
The MSH093E21AXAA wall head is marked "for Multi-Zone only": there is no 9,000 single-zone outdoor unit in Series 21.
Source 2, p. 6; source 3, p. 10The 12,000 modulates from 4,500 to 13,100 BTU/h
In heating, GOODMAN gives the 12,000 a range of 4,500 to 13,100 BTU/h, for a rated 12,000. In cooling, 3,800 to 12,800 BTU/h.
Source 1, p. 6AirGreen × GOODMAN//Who brings what
Series 21, from GOODMAN's table to your wall
What GOODMAN brings
- Three wall sizes, from 12,000 to 24,000 BTU/h, on R-410A
- A published maximum capacity at -8.3, -15 and -25 °C, size by size
- A rated capacity published at -8.3 °C: 7,200, 10,400 and 15,300 BTU/h (06-21 revision)
- A wireless remote supplied with the indoor unit
What AirGreen brings
- Choosing the backup heat for the days Series 21 is not enough
- Installation by our refrigeration technicians, under AirGreen's RBQ licence 5645-9605-01
- Refrigerant lines run within the published limits: 82, 98 or 164 ft depending on size
- The electrical circuit, planned from the published minimum circuit ampacity: 12, 15 or 18 A depending on size
Questions//Series 21
Questions about Series 21
Does Series 21 heat below -25 °C?
GOODMAN publishes Series 21 heating down to -25 °C and gives its last value at that point: 5,800, 7,400 and 11,000 BTU/h at most for the 12,000, the 18,000 and the 24,000. Nothing is published lower. At Montréal-Trudeau, the lowest minimum observed between 1991 and 2020 is -31.8 °C, on January 27, 1994. So we plan backup heat, chosen at the estimate.
Does Series 21 qualify for LogisVert?
Not today. Since November 26, 2025, Hydro-Québec only accepts ENERGY STAR certified heat pumps, and the ENERGY STAR list read on November 5, 2026 holds no Goodman Series 21 wall system. GOODMAN's 2021 brochure and 2018 French document described Series 21 as meeting ENERGY STAR with the right combination; only the ENERGY STAR list counts for Hydro-Québec.
Which size for which room?
In its 2018 French document, GOODMAN prints an "application area": 172 to 252 sq ft for the 12,000, 251 to 368 sq ft for the 18,000 and 330 to 484 sq ft for the 24,000. It is a ballpark: insulation, windows and how the room is used change the answer, which is why the heating needs are assessed on site.
Maximum or rated capacity at -8.3 °C: which one to read?
To know what the unit can deliver in deep cold, the maximum capacity; the rated capacity is for comparing units measured the same way. The GOODMAN 03-21 brochure gives the maximum capacity at 17 °F (-8.3 °C), 12,900 BTU/h for the 18,000; its 06-21 revision gives a rated capacity at the same point, 10,400 BTU/h. They are two different measures, not to be compared with each other.
Does the 24,000 need a bigger wall head than the 18,000?
No. GOODMAN publishes the same wall head size for the Series 21 18,000 and 24,000: 42.5 × 8.9 × 13.2 in, in the 03-21 brochure and in the 06-21 revision. What grows on the 24,000 is the outdoor unit.
Read next//The GOODMAN space
Related pages
A Series 21 in your home: we start with winter
At the estimate, we look at the room to heat, the wall for the outdoor unit and the backup heat you already have. The colder it gets, the less heat Series 21 gives. The size comes after.
Sold and installed by AirGreen.Montreal, Laval, Longueuil, the South Shore and the North Shore.
An AirGreen technician assesses the heating and cooling needs, where the units will go and the refrigerant line route on site before proposing a model.
Subclasses 15.8, 15.10 and 16. Gas and oil work is done by a partner holding the required licence.
The equipment is GOODMAN-branded. AirGreen sells it, installs it and services it across Greater Montreal.
Sources
- GOODMAN, "Heat Pump and Air Conditioner Ductless Units", 19 Series and 21 Series, code CB-DL-1921S-HP 03-21, p. 5 and 6. GOODMAN document kept in AirGreen's files.
- GOODMAN, same brochure, revision CB-DL-1921S-HP 06-21, p. 6.
- GOODMAN, "Thermopompe et climatiseur simple et multizones" (French-language document), code CB-GDuctless2018-FR 10.18, p. 9 and 10.
- ENERGY STAR, certified heat pumps (dataset w7cv-9xjt), Canadian market, read November 5, 2026: no Goodman Series 21 wall system. energystar.gov
- Hydro-Québec, "LogisVert Efficient Homes Program – ENERGY STAR® Heat Pump", partner notice of September 25, 2025 (required from November 26, 2025). hydroquebec.com
- Environment and Climate Change Canada, Canadian Climate Normals 1991-2020, MONTREAL TRUDEAU (AIRPORT), page modified October 22, 2026, read November 5, 2026. climate.weather.gc.ca
Read and dated by AirGreen. Capacities and limits are the ones GOODMAN publishes; a real installation can give other values.