The lifespan of a furnace in New Jersey typically ranges from 15 to 30 years, depending on factors like the type of furnace, its maintenance, and usage. High-quality furnaces that receive regular maintenance tend to last longer. In New Jersey, where winters can be harsh, furnaces are subjected to extended use, which can impact their longevity. Replacing a furnace with a more energy-efficient model as it approaches the end of its lifespan can be a wise investment, helping to lower energy bills and reduce environmental impact.