Whether it is worth replacing a 20-year-old furnace depends on several factors. If the furnace is functioning well and efficiently, it may not need to be replaced. However, if the furnace is experiencing frequent breakdowns, losing efficiency, or having difficulty heating your home, replacement may be worth considering. Also, older furnaces are often less efficient and can result in higher energy bills, so upgrading to a newer, more efficient model can save you money in the long run. Additionally, newer furnaces often come with advanced features and improved comfort control. A licensed HVAC professional can provide a personalized assessment and recommend the best course of action for your specific situation.