Will keeping lights on keep mice away?

Keeping lights on will not reliably keep mice away because mice are not strongly deterred by light alone. Mice are nocturnal and prefer to be active in the dark because it helps them avoid predators, so they are more likely to come out at night, but if they are hungry or have already established nests in your home, they will still move around even with lights on, especially in hidden areas like inside walls, under appliances, behind cabinets, and in attics where light does not reach. Bright lights may make them slightly more cautious and cause them to stick to darker edges and shadows, but it does not remove their motivation, which is food, warmth, and shelter. Studies and pest control experience show that light alone does not cause mice to abandon an infestation. What actually deters mice is removing food sources, sealing entry holes larger than a quarter inch with steel wool and caulk, reducing clutter that provides nesting spots, and using traps effectively. Some people try to combine lights with other deterrents like ultrasonic devices or strong smells, but those also have limited effectiveness. Leaving lights on all night wastes electricity and can disturb your own sleep without solving the mouse problem, so it is not recommended as a control method.