Which characteristic of liquid propane increases its desirability as a fuel for backup generators?

The characteristic that makes liquid propane particularly desirable as a fuel for backup generators is that it does not spoil. This means that propane can be stored for extended periods without degrading in quality or becoming unusable, which is an important consideration for backup power systems that may not be used frequently. This stability allows users to maintain a reliable fuel supply ready for immediate use, crucial in emergency situations when backup power is most needed.

In contrast, other characteristics like flavor and burn rate do not specifically contribute to the functionality of propane as a fuel for generators. Flavor is irrelevant in the context of fuel for generators since it pertains to culinary use, and while burn rate can influence fuel efficiency and performance, the ability to store fuel without spoilage plays a more critical role in ensuring readiness for emergency power needs. Price factors into decisions as well, but it doesn't enhance the operational reliability of the fuel as much as the stability factor does. Therefore, not spoiling stands out as the key characteristic that enhances liquid propane's desirability.