Bats don't chew. They aren't rodents. They are insectivores that swallow bugs whole. So they are not of any risk to chew on electrical wires in your attic. Bats also won't chew on wood, or insulation, or ductwork, or any other part of the attic or house. That said, the accumulation of feces and urine can certainly bury electrical wires and light fixtures, and cause corrosion and electrical outages.
Here is a photo of typical bat damage - you can some piles of bat feces below the roosting areas. Much of the feces is out of sight in eaves or walls.
This isn't damage inside the attic, but the bats in your building will spread feces all over the roof and walls outside. Not really a big deal.
Bat feces, urine, brown fur grease (pictured above) and the bats themselves have a very distinct, pungent odor that most people don't like.
Do bats chew on wires? Rodents, such as mice or rats, are well known for their gnawing ability. It is not only a part of strengthening their teeth, but is simply a behavior that they like to exhibit. Gnawing is what they do and when they are in your home they will chew on virtually any material that they can find.
It can be quite unbelievable the amount of damage that these little creatures can cause. Their teeth are so sharp and there is such a strong desire to chew that they can do an unbelievable amount of damage, especially if given a prolonged period of time to work on it.
If you have a hamster then you know what I am talking about. These little rodents can and will chew through metal attempting to get out of their cage. It seems like nothing is beyond their ability, and the more they chew the stronger their teeth get and soon they are like machines with their ability to get out. It is no surprise, then, that they would successfully chew on wiring and cause electrical issues in your home.
Not every rodent is like this however. While most rodents do chew on things, not all do. The bat is a prime example. These creatures are simply not inclined to gnaw or chew on other things like other rodents. It is just not something they do, regardless of how they are presented in movies.
Many of the bat movies show these critters chewing through wiring to enter a contained area to attack their prey. This is ridiculous, and is another example of Hollywood dramatizing a situation that simply does not occur. Bats simply don’t chew through things.
Because of this, should you have a bat in your home living in your walls you do not at least have to worry about them chewing through the wiring in the walls that is about the only thing positive about a bat being in the wall. Otherwise these are horrible creatures to have in your home.
Bats are terrible animals to have around because they carry parasites and diseases that are hazardous to you and your family. They must be removed from your home as soon as possible and you are going to have a cleanup ahead of you to make your home safe to live in again. At least you do not have to worry about them damaging the electrical wiring of your home. I guess that is the silver lining.