HVAC systems generally last 10 to 15 years. However, your system becomes less efficient and performs worse as it gets older. Therefore, after about 10 years, you may want to start looking for a replacement. Even if you are not having any major problems, modern HVAC systems will save you money on your energy bills because they are more efficient. Plus, they generally come with 10-year warranties, so you won’t need to worry about replacing them for quite a while.