Old thread but just ran into the same thing on a house upgrade. The connected load must be a resistive load. Meaning either it's a light bulb, table lamp plugged into the outlet that's switched, etc.. from the load side of the switch, going to the load itself where it then makes contact with a neutral wire. This completes the circuit a d initiates the glow on the switch with the switch in the OFF position. I had 54 VAC coming to my light with no light bulb inserted into the socket. Illuminated decora was not lit in the OFF position. Screwed in the light bulb and whalah. Switch illuminated. Like the previous person said, it does draw a minor amount of current. To me, this is dangerous and shouldn't be offered to standard applications. The average homeowner changing their light fixtures will be in for a surprise when they think the light switch is off. And yes, people change it without turning the breaker off. This is the first switch I have run into that uses the connected load to operate. And without a connected load, the switch will NOT illuminate. As to be clear, the switch I used isn't a cheap piece of junk. I used a Leviton purchased from Lowes that cost over $10. Personally I think these should be pulled from the shelves until they make a version that adds a neutral for it. And no, sorry to say it does not use the ground that's connected to it to illuminate it. That would be dangerous and cause multiple issues. Yes, neutral and ground are connected at first means of disconnect but the ground is for overcurrent or a lost neutral issue. It is not a normal current carrying conductor.
