Mark wrote:

An empty refrig will cost more to run than a full one... the cold air
flows out when opened... Best would be to fill it with FULL bottle of
water...

I've never found a serious test of this myth on the web. Some serious
energy conservation sites (eg Oregon's) don't mention it.

With more exposed cold surface inside, room air will flow faster through
the fridge when the door is open, with more sensible heat gain and
condensation, which raises energy consumption.

Nick