I've been reading this post with interest,
a couple of years ago I bought, what was at the time the most efficient chest freezer on the market, a Miele GT316e and to be honest was over the moon with it as we're 'off grid' and every Kwh counts.
So pleased with it was I that I recommended it to another 'off gridder' who purchased the smaller model which died after 24 hours use between Christmas and Hogmanay ( probably as a result of low ambient temp as it was kept in an out building ).
The engineer finally came to it last week but unfortunately the compressor was toast (or words to that effect) upon explaining to my mate what I'd read here he phoned up Miele.
I'm not sure of the exact words but basically they told him to turn up the heating to make the freezer efficient

Cheers, Paul