We've heard stories from people that hung a bat house and never received a tenant and stories from folks that had bats within a couple weeks.  Bats are very intelligent and therefore quite particular about the places in which they like; you will receive the best results by following these recommendations.  A bat house should be hung at least 10 to 15 feet above the ground, sheltered from the wind, and unobstructed by obstacles to flying, such as power lines and tree branches. Bat houses located near a source of water, especially a marsh, lake, stream, and swimming pool are most likely to attract bats, as this habitat attracts insects and provides a plentiful food supply for the bats. To keep the interior very warm, place the house on the side of a building or tree which receives several hours of morning or afternoon sun (100-110 degrees F is required by nursery colonies). If you are located in a cooler climate you may want to stain or paint house a dark color to absorb sun energy. If you are located in a warmer climate the bat house can be painted a beige or tan color using latex pain, or mounted as is. The pine wood will weather nicely to an attractive silver gray color which blends well with outdoor environments.