Is your old furnace 15 to 20 years old and due for replacement? Before you commit, compare your options. For furnace replacement in Calgary, the choice between single-stage, two-stage and modulating furnaces affects your comfort, gas bills and upfront cost for the next two decades. Our easy guide covers typical price ranges, who each type suits and what to ask your contractor. That way your furnace replacement is a smart investment, not just a quick swap.