Hi Mate, You can't run many electric guns on Co2, I can't really answer the efficieny question as I don't know but I've shot a hopper and 5 pots off a 3k fill so pretty good and yes I can do a deal with a reloader.
But if your next response is 'Ok I'll ask my parents if I can buy it' or 'Can you save it till I get my pocket money on Saturday' please don't bother as I've had 5 of them this month already