Most high-quality bat houses are occupied within a few months to a year. I would re-evaluate the appropriateness of the location if after two years your bat houses still haven’t been occupied. Some of the most successful houses that Merlin Tuttle has observed took 12-18 months to be occupied. There was one that was on a shaded side of a building went unused for five years. But when moved to a sunny spot just 50 feet away on the same building, it attracted more than it could hold in just a few months. Some were actually hanging out the bottom or clinging to the outside, apparently desperate to stay with their colony. Always feel free to email us photos of your BatBnB and we can give you an evaluation on the location you’ve selected. Location is key!