If you are renting a public storage facility, chances are you’ve got too much stuff. Sell something and make room at home. Not only will you gain a bit of money from the sale, you’ll save 100% of the storage rental fees.
There are some very specific justifications for public storage, but even in those rare cases you’ll be better off if you can store your stuff with family or friends.
This is an easy savings of $30-$100 per month, or more.