Similar to cars, air conditioners use up a large amount of power to 'get the engine running.' The high electricity demand can temporarily disable nearby appliances—like your lights. Observe your lights the next time they start to flicker. If they dim for less than a second and only lose a fraction of their brightness, it's likely not a cause for concern. If the flickering is constant or the lights brighten or dim significantly, there might be an underlying electrical problem that needs immediate attention.