Rent Premium for a Storm Cellar in SW Oklahoma City?

[Clay Scott]

I just purchased my first ever investment property. I'll soon be done with the renovations and I'm excited to get it rented. The previous owner/occupants installed a storm safe in the garage (see https://goo.gl/21afSb for a photo of the type of shelter). The house is located in SW Oklahoma City where tornadoes aren't uncommon. (It's 3 miles from the path of the deadly 2013 tornado that struck Moore, OK.)

Is there a premium to be added to the rent because of this feature? If so, about how much ($ or %) could I expect to add to the base rent?

Thanks in advance.