A two-stage furnace runs on a low setting most of the time and only switches to full power on Calgary's coldest days. Most of our long heating season isn't −30°C, so you get steadier temperatures, quieter operation, less on-off cycling and better air filtration. Our new guide explains why a two-stage furnace is the sweet spot for most Calgary family homes, especially two-storey houses with uneven upstairs rooms. It also shows how two-stage compares to single-stage and modulating options.