We use them in our VERY open pole house in the rainforest - small bats fly around inside the house and set up camp in the joins of the wooden roof beams.
These lamps seem to deter them. Not fully but using about 6 of them throughout the house has significantly reduced the number of bats coming inside by a large margin.
Be aware that if the lamp goes out (or you turn the light off) the salt will start to melt and create pools of water.