What is the difference between natural gas vs propane?

Both units create flame by burning some sort of fuel which in the case of gas units runs through either natural gas lines already installed in your home (if you have access)or propane tanks installed outside of your home, but the difference comes down to what’s powering those flames. Natural gas is a more affordable option since it doesn’t require any sort of external tank and creates heat by creating smaller carbon monoxide molecules that burn hotter than propane which results in less fuel being used over time as well as an easier start-up process.