If you have a residential fridge it is most likely self defrosting don't know of a 2 way that is. Depending on the humidity we defrost the fridge twice a year. We are presently at 8100 ft with low humidity freezer is starting to grow some frost in the rear may defrost next week before we head to the flatlands. Adverage humidity up here is around 20 percent though days about 80 degrees temps with 15 percent humidity and nights in the high 40's with humidity in mid 30's.