Quoted from hjh632:A game uses about 300w per hour. At 13¢ a kwh that's about 3 hours for 13¢. If left on for 24 hours that would cost about $1 per day per machine. Depending on your machine and local rates the cost per day may be 50¢.
I have measured power consumption on my LED'd EM's and they average 1.2A while not being played. A bit more during actual game play. If the 13 cents per kWhr rate is used, that's 1.2x120/1000x24x0.13=45 cents a day or $13.50 a month.