opposite of 'lights-out', which in factory terms means a factory that's sufficiently automated that it can operate most of the time with the lights turned off because there's no people inside.
There's a similar concept in food delivery, where restaurants that only deliver food (eg Doordash / Uber Eats only) and don't have a physical store for customers are called Dark Kitchens. They try to automate as much of the food preparation as well.