Air conditioners have a shorter lifespan than furnaces since they are exposed to higher temperatures and spend more time outside. Modern air conditioners system have a lifespan of up to 15-20 years, compared to the 10–12 years of older models.    Boilers and furnaces typically last 15 to 20 years, geothermal equipment for 30 years, water heaters for ten years, and tankless water heaters for 20 years.