So long as there's an existing light fixture, this job is a cinch: Kill the power, remove the old unit, and wire up the new one, says TOH's go-to master electrician, Scott Caron. "Hot" black wire to black, neutral white to white, and don't forget to connect the green ground to the bare copper wire wound around the ground screw. "Really," he says, "the most important thing is to buy a high-quality unit." Sophisticated circuitry guards against false triggers, and you can adjust the sensor to ignore animals—or not. "I like to know when our neighborhood skunk is around so I don't get surprised," Caron says. Set the light to test mode and aim the sensor so that it doesn't pick up traffic or pedestrians. Or late-night hot-tub action.