I took some measurements on the AC side using two different wall warts to see what the current flow would be with the load on and off. With the load off, the AC side sees about 100 mW. That's quite a lot, given that the theoretical DC load should be 800 µA or less at 5 volts (< 5 mW), but nobody ever said that wall warts were terribly efficient at low draw. With the load on, the AC side sees just over 5 watts of load. Given the theoretical DC load of about 2.7 watts or so, that's about 50% efficiency. Not... fantastic. The standby load will wind up being about a kW-hr per year. About the only way to make it any better would be an arrangement where the button would momentarily turn on AC power where it would be held on by an SSR for the timing duration. That's certainly possible, but it does complicate the design quite a bit (and raise the cost).