Quoted from EJS:If you have a TZ and TAF I wouldn’t go beyond those on one. I’d say 4 is good but I’ve run 5 if they aren’t power hogs.
LEDs will make a difference for you too. Incandescent GI is like having an extra toaster plugged in.
It probably indeed depends on the age and lighting used by the machines.
I have these 6 hooked into a single 20 amp strip plugged into a single 20 amp outlet all going at the same time without issues:
Attack From Mars Remake LE
Medieval Madness RE
STNG
Munsters Premium
Stranger Things Premium
VCab with Intel i7, shaker, high end sound system, 42 inch 4k HDR playfield, and 32 inch 1080p backglass.
Haven’t thrown the breaker on the strip or the electrical box. I have 4 outlets total for my arcade each receptacle has its own dedicated 20 amp breaker in a dedicated 100amp box.
If you want I could hook up my power sensor to it this weekend and and get an idea of what the actual active load is. I’ve been meaning to do it but since everything is working I haven’t needed to. 
