Sky boxes don't have a standby mode, they never turn off.Set top boxes aren't that much, maybe 40 - 60w during operation. 5 - 10w in standby? The TV will be more than a top box.
You may think they do as they trick you into thinking it does, but it never actually goes off, plenty of tests done already on it.
Other set top box devices (along with everything else) should be tested (hand ontop is usually all thats needed). Something as stupid as having a PLUG in the socket, even without something plugged into the other end will be drawing power as it will be warm to the touch.