Frost free freezers
The interior coils of frost free freezers are designed to heat up to prevent ice buildup. They generally cost more than manual defrost freezers (See Reference 1).
Manual defrost freezers
Manual defrost freezers will eventually build up ice within the storage compartment and need to be defrosted to keep the unit in good working condition.
Upright or chest freezer?
Chest freezers use about 10 to 25 percent less energy than upright freezers, and are less likely to be frost free than uprights. They are usually less expensive than uprights (See Reference 2).
Manual defrost freezers are much more energy efficient than their frost free counterparts. They use about 40 percent less electricity.
To manually defrost a freezer, you will have to remove the contents, unplug the appliance for a few hours, then remove the chunks of ice as they melt. Check the owner's manual (See Reference 3).