Bat houses are an important component for creating habitat for bats. Bat houses provide a summer roost and a suitable home for females to raise their young.
If you get a bat exclusion on your home, installing a bat house in the yard can provide a new home for bats. Bats will not likely leave your house - in preference of a bat house. Once they are established in an attic, you need to make them leave.
A bat house may help reduce the odds that the colony will move into a neighbor's home. Installing a bat house not only helps the bats, it may help a neighbor.
Regardless, having a bat colony in the yard, is very entertaining - and they will help keep the bug population down.
Bat Houses should be installed so that they face South or Southeast, so they receive early morning sun. Bats prefer a warm environment. Here is some data from Critter Catchers Funded Research through our scholarship.
If bats do not occupy the bat house within a couple years, move it to a new location.