I really do hate keymeters....
When we lived in the UK it was the first thing I did when we moved into the rental house was change from a key meter to a normal one...and the same when we bought the flat....
For those of you in the ROTW that don't know what they are, they are an electicity meter that you have to insert a 'charged key' into. You go to a charge point...newsagent, local shop etc, and pay 'x' amount....(5, 10 20 pounds etc) to have the key topped up. You may be able to do this online now, but you couldn't 7yrs ago. You then insert the key into your electric meter and bingo, power flows. You can go into 'debit' by a small amount, but not much, and the meter will keep working when you pull the key out for a short period too...but from my point of view, they are a pain in the butt.
Basically, you pay for the power before you use it and it does help moderate how much you use and can stop you getting massive bills....