Did he clean the condenser and replace the door seal? Dirty/clogged condensers and leaky door seals have a huge effect on efficiency.
Also, if his is not a chest freezer, that's another big difference --- a chest freezer is inherently better if opened often, since the cold air stays at the bottom, whereas in an upright one, it spills out.
Yes another chest freezer - and yes that usage is pretty good for a freezer of that age - when I've tested other brewers set-ups they can be even worse (but that is often when they've clad them in wood - looks cool but stops the freezer cooling properly...)
I'll get them to check it is clean, but I'll assume it is as he's pretty on top of that sort of thing.
