An oversized furnace isn’t a better furnace. Too much heat can actually make your living spaces less comfortable in winter, not more. It’s also wasteful from an energy efficiency standpoint, as well as a from a financial one.
In the past, residential furnaces were often "one-sized" rather than installed on the basis of an accurate load calculation of the actual thermal requirements of the home. To cover for the inevitable errors in this process, builders and contractors simply installed a furnace that was too big for the job. Many homeowners are stuck paying for these past mistakes.
Here are some of the ways an oversized furnace is bigger but not better.