How many BTU for my house? (heat pump BTU calculation)
Step 1: quick calculation in 4 answers →Estimate only: floor area, region, insulation and current heating. Final validation afterwards with the full calculator.
How many BTU per square foot does a heat pump need in Québec?
About 16 to 20 BTU/h per sq ft according to Hydro-Québec’s two rules of thumb, or 12,000 to 15,000 BTU/h for 750 sq ft. It is a starting point, not a sizing: Hydro-Québec notes that its rule “may vary with various factors, including the type of building and its geographic location” (Hydro-Québec).
| Area to heat | 12,000 BTU/h per 750 sq ft (cooling) | 15,000 BTU/h per 750 sq ft | Site calculation, Montréal, average insulation | Site calculation, Saguenay, average insulation |
|---|---|---|---|---|
| 750 sq ft | 12,000 | 15,000 | 12,000–15,000 | 14,000–17,000 |
| 1,000 sq ft | 16,000 | 20,000 | 16,000–20,000 | 18,000–23,000 |
| 1,500 sq ft | 24,000 | 30,000 | 24,000–30,000 | 28,000–34,000 |
| 2,000 sq ft | 32,000 | 40,000 | 32,000–40,000 | 37,000–46,000 |
Rules of thumb: area × 16 or × 20 (site calculation from Hydro-Québec’s two rules). “Site calculation” columns: same code as thehome page estimator (area × 16 to 20 BTU/h per sq ft, climate factor from ECCC degree-days, average insulation × 1.00, 8 ft ceiling), rounded to the nearest thousand. Order of magnitude only.
Hydro-Québec also gives ranges by type of home: 12,000 to 24,000 BTU/h for a condo, 24,000 to 48,000 BTU/h for a single-storey house and up to 65,000 BTU/h for a two-storey house (Hydro-Québec). They are wide because they account for neither the exact area nor the insulation.
Why does Hydro-Québec give two different rules (12,000 or 15,000 BTU/h for 750 sq ft)?
Because they do not aim at the same thing. The 12,000 BTU/h per 750 sq ft rule is a cooling capacity: Hydro-Québec advises calculating capacity “based on cooling needs” to avoid an oversized unit “that does not dehumidify the air well in summer”, and because trying to meet all heating needs with a heat pump “would not be economical” (Hydro-Québec). The 15,000 BTU/h for 750 sq ft rule comes from its “Seven points to consider” article, which ties it to the area to be heated (Hydro-Québec). The gap between the two is 25% (site calculation).
The site uses both as the low and high ends of its range, then adjusts it for climate, ceiling height and insulation (estimator method).
In Québec, does heating or cooling set the size?
Heating, because it is the larger need. Hydro-Québec writes that “in Québec, heating needs are greater than cooling needs” and, citing Natural Resources Canada, that “heating capacity matters more than cooling capacity” (Hydro-Québec). Québec.ca goes further: “Although retailers tend to recommend a size that is ideal for summer cooling, it is essential to choose a larger model that will heat your space efficiently in winter” (Québec.ca).
For scale: in an example from NRCan’s sizing guide, a house has a design heating load of 49,600 BTU/h at −20 °C and a design cooling load of 23,500 BTU/h at 31 °C (NRCan guide), about 2.1 times more for heating (site calculation). A unit chosen for cooling alone therefore covers only part of the winter; backup heat does the rest.
Also, an air-source heat pump’s capacity drops in the cold: “any drop in temperature reduces the heat pump’s capacity to absorb heat”. Below the thermal balance point, it only partly meets the need and backup heat takes over (NRCan). NRCan’s guide strongly recommends using manufacturers’ extended performance data, which give the capacity at low temperatures (NRCan guide). To read them: how to evaluate a heat pump.
Should the heat pump cover all the heating or only part of it?
It is a choice, and it changes the size. NRCan’s sizing guide offers four options depending on your goals (NRCan guide):
| Option | Role of the heat pump | Target capacity | Example (BTU/h) |
|---|---|---|---|
| 4A: emphasis on cooling | Cools; some heating in mild weather | 80% to 125% of the cooling load | ≈24,000 of cooling (Hydro-Québec rule) |
| 4B: balanced | From most of the heating in mild weather to most of the season | Same cooling target, with a two-stage or variable-speed unit chosen to heat more | Same as 4A |
| 4C: emphasis on heating | Most of the heating in mild to cold weather; backup in deep cold | Heating load at −8.3 °C (guide equation 4) | ≈15,000–19,000 at −8.3 °C |
| 4D: design load | All or nearly all of the heating; cold-climate model needed in most of Canada | Heating load at the design temperature | ≈24,000–30,000 at −23 °C |
Example: the estimator range (24,000–30,000 BTU/h) is treated as the heat loss at Montréal’s design temperature, −23 °C (NBC 2020, Table C-2), as in thequick estimate (site assumption). At −8.3 °C: × 43 ÷ (60 − (−9.4 °F)) = × 0.62 (NRCan guide equation 4), rounded to the nearest thousand. 4A: 1,500 × 16 (Hydro-Québec rule). Order of magnitude only.
If you keep your baseboards as backup, the guide notes that the risk of undersizing the heat pump is largely mitigated (NRCan guide). For a wall unit added to a house heated with baseboards, size it on the area it serves: the guide splits the house load by floor area, for example 49,600 × 1,130 ÷ 3,310 ≈ 16,900 BTU/h for a 1,130 sq ft area in a 3,310 sq ft house. A wall unit in an open area can also partly heat the upper floor through an open stairway. For the effect on the bill: heat pump vs baseboard heaters.
The LogisVert rebate also depends on the capacity at −8 °C: Hydro-Québec gives the example of $1,800 for a very high efficiency model of 15,000 BTU/h at −8 °C and $3,600 for 30,000 BTU/h (Hydro-Québec). Detailed calculation: LogisVert rebate at −8 °C.
What happens if the heat pump is too big or too small?
In both cases, the expected savings may not materialize (NRCan):
- Too small: the backup heating system is used more often, and you may not get the expected savings.
- Too big: in mild weather, it “produces too much heat and the unit cycles on and off, which causes discomfort and wear on the heat pump”.
- In summer: an oversized unit does not dehumidify the air well (Hydro-Québec).
How do insulation and region change the number of BTU?
Yes: the same floor area can need more or less capacity depending on the house. Québec.ca lists the variables to consider: area and volume, layout and orientation, geographic location, type of construction, insulation and airtightness, and the size, type and orientation of the windows (Québec.ca). Hydro-Québec points out that good insulation is essential and that better airtightness prevents heat leaks (Hydro-Québec).
| Region | Design temperature | Good insulation | Average insulation | Poor insulation |
|---|---|---|---|---|
| Montréal | −23 °C | 22,000–27,000 | 24,000–30,000 | 28,000–35,000 |
| Québec | −25 °C | 24,000–29,000 | 26,000–33,000 | 30,000–38,000 |
| Saguenay | −31 °C | 25,000–31,000 | 28,000–34,000 | 32,000–40,000 |
| Sept-Îles | −29 °C | 26,000–33,000 | 29,000–36,000 | 33,000–42,000 |
Site calculation, same code as the home page estimator (8 ft ceiling, rounded to the nearest thousand). Insulation factors 0.90, 1.00 and 1.15: estimated by the site and deliberately modest, because we found no official coefficient. Design temperature: NBC 2020, Table C-2 (January 2.5%), for reference; see the Québec design temperatures.
To measure the actual effect of your walls, windows, ceiling, basement and air leaks, use the heat-loss calculator (surface by surface). If you have a recent EnerGuide evaluation report, it may state the house’s design heating and cooling loads (page 2 of the report, according to the NRCan guide).
What is the CSA F280 standard and should you ask for it?
It is the reference calculation method. NRCan recommends that heating and cooling loads be “determined using a recognized method, for example CSA F280-12, ‘Determining the Required Capacity of Residential Space Heating and Cooling Appliances’” (NRCan). According to NRCan’s guide, building codes require this calculation for new houses; it also suits an existing house after major envelope upgrades. Otherwise, the guide suggests an energy audit, HOT2000 modelling or, as a last resort, the capacity of the existing equipment (NRCan guide). In that last case, it treats 125% of the design load as a reasonable minimum margin and notes that 140% was the upper limit in CSA F280 until 2012.
This site’s calculators are not CSA F280 calculations: they are estimates to prepare the discussion with the installer.
What should you ask the installer before choosing the capacity?
A written, justified number, not just a unit size. Questions to ask:
- What is the heating load of my house (or of the area served), in BTU/h, at my design temperature ? Using which method: CSA F280, energy audit, HOT2000?
- Which option are you aiming for: cooling, partial heating or full heating? (options 4A to 4D in the NRCan guide)
- What is the proposed model’s heating capacity at −8 °C, at −15 °C and at my design temperature, according to the manufacturer’s data? (how to read a spec sheet)
- At what outdoor temperature will backup heat take over, and which one?
- For a central system: can the existing ducts carry the required airflow? NRCan’s guide notes that their capacity can limit the size of the heat pump.
- Does your licence cover this work? (check the RBQ licence)
Québec.ca suggests having your needs calculated by a heating professional accredited by the Corporation des maîtres mécaniciens en tuyauterie du Québec (CMMTQ) and using more than one professional to check and validate the results (Québec.ca). Compare the loads from one quote to the next: a large gap deserves an explanation.
How can you estimate it yourself before calling an installer?
- Quick calculation in 4 answers : area, region, insulation and current heating (1 minute).
- Find your design temperature (NBC 2020, 124 localities).
- Calculate the heat loss level by level: walls, windows, ceiling, basement, air leaks.
- Compare models on their capacity at −15 °C and at your design temperature.
- Estimate the LogisVert rebate from the capacity at −8 °C.
Frequently asked questions
12,000 or 18,000 BTU heat pump: which one?
Using Hydro-Québec’s rules of thumb (16 to 20 BTU/h per sq ft), a 12,000 BTU/h unit matches about 600 to 750 sq ft and an 18,000 BTU/h unit about 900 to 1,125 sq ft (site calculation). For heating, compare instead the model’s capacity at −15 °C and at your design temperature with the heat loss of the area it serves; baseboards you keep provide the backup.
How many BTU for a 1,000 sq ft house?
About 16,000 to 20,000 BTU/h according to Hydro-Québec’s two rules of thumb. The site’s estimator gives 16,000–20,000 BTU/h in Montréal and 18,000–23,000 BTU/h in Saguenay (average insulation, 8 ft ceiling). It is an order of magnitude: have it confirmed by a load calculation.
Does a more powerful heat pump heat better?
Not necessarily. According to NRCan, an oversized heat pump runs inefficiently in mild weather and cycles on and off, causing discomfort and wear; if it is too small, the backup heat runs more often. What matters is its capacity in deep cold compared with the house’s heat loss.
Does this site’s calculation replace a CSA F280 calculation?
No. The site’s tools give an order of magnitude. NRCan recommends determining heating and cooling loads with a recognized method, for example the CSA F280-12 standard: ask your installer for this calculation.
Sources
- Hydro-Québec, Heat pump: how to determine the right capacity for your home? and Seven points to consider before buying a heat pump. Checked October 28, 2026.
- Québec.ca, Heat pump (page updated December 17, 2025). Checked October 27, 2026.
- Natural Resources Canada, Heating and cooling with a heat pump (page modified December 24, 2025). Checked October 27, 2026.
- Natural Resources Canada, Air-Source Heat Pump Sizing and Selection Guide (version 1.0, December 21, 2020), steps 3 and 4.
- National Research Council Canada, National Building Code 2020, Table C-2 (design temperatures), via our Québec design temperatures.
See also: the quick calculation · the quick estimate · heat loss · the LogisVert rebate · heat pump vs baseboards · all tools.