Furnace and heat pump sizing in New Brunswick
Fredericton runs about 4,601 heating degree-days a year, which puts it in the cold band at roughly 50 BTU per square foot of heating. The rest of the province sits in the same band.
New Brunswick is unusually uniform: Fredericton, Moncton and Saint John land within about fifty degree-days of each other and share one band. The Bay of Fundy does moderate Saint John — its January nights run more than a degree warmer than Fredericton’s — but that same water keeps the shoulder seasons cool, so Saint John ends the year needing marginally more heating, not less. It is a good illustration of why a mild January does not mean a small heating load.
Heating degree-days and January temperatures in New Brunswick
Degree-days below 18 °C and January temperatures from the Environment and Climate Change Canada Canadian Climate Normals 1991–2020. The band column applies the mapping described on the Canada index.
| City | Heating degree-days (18 °C) | January daily mean | January daily min | Band | BTU/sq ft |
|---|---|---|---|---|---|
| Fredericton | 4,601 | -9.2 °C | -14.6 °C | Cold | ~50 |
| Moncton | 4,614 | -8.4 °C | -13.3 °C | Cold | ~50 |
| Saint John | 4,649 | -7.9 °C | -13.2 °C | Cold | ~50 |
How the province compares to itself
Worked example
Take a 1,500 sq ft home in Fredericton. At the cold band of 50 BTU per square foot:
1,500 sq ft × 50 BTU/sq ft = 75,000 BTU/h
A gas furnace is rated by input, so divide the output by the AFUE to get the rating you shop for: at 95% AFUE that is about 79,000 BTU/h of input. That falls between the standard 60,000 and 80,000 BTU/h sizes. Which one you should buy is exactly the question a load calculation answers and a rule of thumb cannot — rounding down leaves the house short on the coldest nights, and rounding up brings the short-cycling problems of an oversized furnace. Run your own numbers in the furnace-size calculator, and use AFUE typical bands if you do not have the nameplate.
Heat pumps in New Brunswick
A heat pump loses capacity as the outdoor temperature falls, exactly when the house needs the most heat. The temperature where its output equals the house load is the balance point; below that, backup heat makes up the difference. Fredericton averages a January daily minimum around -14.6 °C, and the design condition is colder still.
At these degree-days a heat pump needs a genuine cold-climate rating and backup heat sized to carry the house on its own at the design condition, not merely to supplement. Rated capacity at 8.3 °C tells you almost nothing about performance here; ask for the capacity table at low outdoor temperature.
The heat-pump-size calculator works from the same band, the balance-point calculator finds the crossover temperature. Dual fuel and the balance point explains where backup heat takes over.
A note on units
Canadian homes are almost always described in square feet and equipment is rated in BTU/h or tons, but outdoor temperature is in °C and degree-days are on the 18 °C basis rather than the American 65 °F. The two degree-day scales are not interchangeable: an American HDD65 figure is about 1.8× the Canadian HDD18 number for the same place. Every degree-day figure on this page is the Canadian 18 °C basis. If you have a floor area in square metres, multiply by 10.76 to get square feet before using the calculators.