Wattage sensors will send a red signal if a dupe is currently tuning up a generator that is attached to a power system that its on.
Steps to Reproduce
Build a wattage sensor and set it to send a green signal (with a filter gate set after it to 20 seconds so you can see it happen) if below 1 threshold (basically if no power is running through the wire) along a wire that is connected to a transformer (with battery in case that makes a difference). Have the generator that powers the transformer inside a power plant room and have a dupe tune up the generator and see the wattage sensor suddenly send a red signal.
This issue has not been confirmed by a developer yet.