When replacing the outdoor unit, should the indoor unit also be replaced? At Mitchell Heating, we do recommend replacing both your indoor and outdoor units at the same time because: Nowadays, outdoor systems are built to work with their matching indoor system for the most efficiency. When you replace one system but not the other, you may not see the same savings on your energy bills as if you had replaced them together. Thanks to technological innovation, newer systems mean better efficiency. This is true for heating and cooling products as well. While the advancements focus on greater heating and cooling efficiency, they also include benefits such as better air handling, filtering and noise reduction. If your heating and cooling systems are over 10 years old, they need to be replaced. Older models have outdated technology that is likely adding to your energy costs due to poor efficiency. So by replacing your indoor system at the same time as your outdoor equipment, both your systems will provide better energy efficiency that helps you lower your energy bills and keep your home more comfortable.