You can get food very crispy in a dehydrator if you dehydrate it for a longer time. It's a great appliance for giving food a kind of cooked or baked flavor without heating it excessively, so it remains "alive." This means that below 42°C (108°F), the enzymes in the food remain active. Just like in our bodies: at temperatures above 42°C (108°F), our enzymes begin to degrade, and irreversible damage can occur.
Some people also use dehydrators at higher temperatures; this dries vegetables, fruit or other foods much faster, but they also lose many more nutrients.
Energy balls I usually make without a dehydrator...and store in the fridge. But I have made cookies and crackers too...