Quick heat-loss estimate (step 1)
What is your home’s approximate heat loss?
Site calculation: a 1,500 sq ft house with average insulation and no heated basement loses about 24,000–30,000 BTU/h in Montréal (−23 °C) and 26,000–33,000 BTU/h in Québec City (−25 °C). The heat pump should then deliver about 19,000–24,000 BTU/h at −15 °C in Montréal, or be supplemented by backup heat.
How is this estimate calculated?
It reuses the home estimator’s calculation, with no new coefficient: heated area × 16 to 20 BTU/h per sq ft, × climate factor, × insulation factor. The site treats this range as an order of magnitude of the heat loss at the design temperature (site assumption).
| Parameter | Value | Source |
|---|---|---|
| Base per sq ft | 16–20 BTU/h | Two Hydro-Québec benchmarks: 12,000 BTU/h per 750 sq ft (determining capacity) and 15,000 BTU/h per 750 sq ft (seven points to consider). |
| Heated area | above basement + heated basement | Same per-sq-ft rule applied to the heated basement; the full calculator handles below-grade walls separately. |
| Climate factor | 1 + 0,5 × (DJ ÷ 4 363 − 1) | ECCC degree-days for the location, as on thehome estimator; weighting: site estimate. |
| Insulation factor | 0,9 · 1 · 1,15 | Site estimate (good, average, poor), same as the home estimator. |
| Design temperature | January 2.5% | NBC 2020, Table C-2 (see Québec design temperatures). Beauce: location not listed, no value estimated. |
| Capacity at −15 °C and −25 °C | × (60 − T °F) ÷ (60 − design T °F) | Equation 4 of the NRCan sizing guide (load proportional to the difference from 15.6 °C), applied by the site at −15 °C and −25 °C. |
What is the heat loss of a 1,500 sq ft house?
Results of the calculation above, rounded to the nearest 1,000 BTU/h. At −25 °C, the capacity to look for exceeds the design heat loss when the location’s design temperature is milder than −25 °C.
| Location | Design temperature | Design heat loss (BTU/h) | Capacity to look for at −15 °C (BTU/h) | Capacity to look for at −25 °C (BTU/h) |
|---|---|---|---|---|
| Montréal (City Hall) | −23 °C | 24,000–30,000 | 19,000–24,000 | 25,000–32,000 |
| Québec | −25 °C | 26,000–33,000 | 20,000–25,000 | 26,000–33,000 |
| Saguenay (Bagotville) | −31 °C | 28,000–34,000 | 18,000–22,000 | 24,000–30,000 |
| Sept-Îles | −29 °C | 29,000–36,000 | 20,000–25,000 | 26,000–33,000 |
| House | Design heat loss (BTU/h) | Capacity to look for at −15 °C (BTU/h) | Capacity to look for at −25 °C (BTU/h) |
|---|---|---|---|
| Recent or renovated (good insulation) | 22,000–27,000 | 17,000–21,000 | 23,000–28,000 |
| Average insulation | 24,000–30,000 | 19,000–24,000 | 25,000–32,000 |
| Older, poorly insulated | 28,000–35,000 | 22,000–28,000 | 29,000–37,000 |
| Average insulation + 750 sq ft heated basement | 36,000–45,000 | 29,000–36,000 | 38,000–47,000 |
What should you do after this first estimate?
- Validate with the heat-loss calculator (walls, windows, ceiling, basement, air leakage).
- Compare models with the guide how to evaluate a heat pump : capacity at −15 °C and −25 °C, COP, HSPF2, official lists.
- Have the sizing with a CSA F280 calculation by an RBQ-licensed contractor.
Frequently asked questions
Why two calculators?
This one gives an order of magnitude from four answers, based on floor area. The heat-loss calculator adds up walls, windows, ceiling, basement and air leakage, level by level: it is the final check before comparing models.
Where do the capacities at −15 °C and −25 °C come from?
From equation 4 of NRCan’s sizing guide, which assumes a load proportional to the difference between 15.6 °C (60 °F) and the outdoor temperature. The guide applies it at −8.3 °C; the site applies it at −15 °C and −25 °C, two temperatures where manufacturers and the NEEP list publish data.
Is my data sent anywhere?
No. The calculation runs in your browser and nothing you enter is transmitted.
Sources
- Hydro-Québec, How to determine the right capacity and Seven points to consider before buying a heat pump. Checked October 20, 2026.
- NRCan, Air-Source Heat Pump Sizing and Selection Guide, Step 4, equation 4.
- NRC, National Building Code of Canada 2020, Division B, Appendix C, Table C-2.
Step 2: full heat-loss calculator →
How to evaluate a heat pump →