The size of the furnace you need for your house depends on various factors, including the square footage of your home, the climate in your area, the quality of insulation, the number of windows and doors, and the specific heating requirements. To determine the appropriate furnace size, it's crucial to perform a heat load calculation, often called a Manual J calculation, which takes all these factors into account. This calculation ensures that the furnace's heating capacity matches the specific needs of your space, preventing issues like underheating or overheating. Oversizing or undersizing a furnace can lead to inefficiency, increased energy costs, and discomfort. Consulting with an HVAC professional who can perform a heat load calculation is the best way to determine the correct furnace size for your home.