You should consider design when selecting your bat house. According to research, larger bat houses (often called nursery houses) have higher occupancy rates than the smaller houses. All landing areas and partition surfaces should be rough. Vents are often best where average July temperatures exceed 85 degrees Fahrenheit.
Your bat house should be placed within 1/4 mile of a natural water source such as a stream, river, or lake. Bats tend to fly along forest or water edges, and bat houses located here tend to be found more quickly than other locations.
You may place your bat house on a tree, pole, or a building; however, boxes mounted on poles or buildings tend to have a higher occupancy than those mounted on trees. For mounting on buildings, wood or stone buildings are best, and your bat house should be mounted under the eaves with some sun exposure. You should mount your house 15-20 feet above the ground. It should not be in a brightly lit area.
You should place your bat house where it will receive at least six hours of sun if you live in a region where average July temperatures range from 80-100 degrees Fahrenheit. If you live in a region where average July temperature are less than 80 degrees Fahrenheit, you should mount your bat house where it will receive at least 10 hours of sun.
You may mount your box at any time of the year, but those boxes mounted in the spring are often occupied more quickly. If you are evicting a colony of bats from a building, a box should be mounted several weeks prior to the eviction.