The time it takes to install a new furnace can vary based on several factors including the complexity of the installation, the availability of the installers, and whether or not old equipment needs to be removed and disposed of. Generally speaking, a standard furnace installation might take anywhere from 4 to 10 hours. Complex installations that require additional ductwork, electrical work, or removal of an old furnace may take longer, potentially extending to 1-2 days. It’s best to consult with your installation professional for a more accurate time estimate based on your specific situation.