Gomen, I guess I just missunderstood. The better my Japanese gets the worse my English gets you know... but just like J44xm said, around 3000-7000, it all depends on what season it is, as well as how many electric things you got. For example me and my husband both have a computer each (to avoid fights you know XD) and during the winter we`ve been mostly using the airconditioners to keep us warm, as well as a hot bath every evening. The water bill is pretty steady around 3000-3500 yen, gas around 5000 last month (usually around 3500-4000, higher last month because of the weather suddenly getting really cold) and the electricity for last month was as high as 8000 yen, for the same reason. It was pretty steady around 6500-7000 during the summer, and as low as 3000 during autumn when we didn`t need to use niether heating or cooling.
So all in all, as mentioned before, it all comes down to what season you`re in and what kind of life you lead. If it weren`t for my obsession with hot baths perhaps we`d have more money to spend on karaoke at the end of each month... *sigh*