Our answer is, it’s a smart method. Here's why. Paired design—Your furnace. This might help enhance energy efficiency and performance. Technology enhancements—There have been a lot of recent increases in HVAC technology, especially in energy efficiency, air filtration and quiet operation. You’ll get these benefits year-round when you upgrade the complete system. Improved heating and cooling efficiency—Efficiency ratings are based on matched equipment performance. While getting one new unit will improve performance, efficiency will be decreased from what it was envisioned to be. And your savings will not be as large as they’d be with matching units. Equipment age—If your AC is 10 years old (or older), your heater is likely just as outdated. Replacing both means you’ll have a lot of of years of efficient comfort, regardless of the time of year. Updated warranty—A new system also means you’ll have new system warranties. You’ll have peace of mind when you realize the warranty protects your entire system for the same time period. On the surface, installing just a new cooling system or heater might feel like a bargain. But it’s not a great bargain when you consider decreased efficiency. Getting an entirely new system could be costlier, but you earn much more efficiency, reliability and comfort for long into the future in North America.