I'm an electrician.
vid1900 caused me to grab my meter and do some checking:

1993 DMD game - with LEDs - pulls 1.2 amp in attract mode
When put into game play and fooled into searching for the balls by operating all of the coils and kickouts - amps periodically spike up to 3 amps but only for a second or less.

1984 Solid State - no LEDs - pulls 1.8 amps in attract mode - less when put into play.

I really thought they used more power.
I will also support his recommendation to hire a professional.
In my opinion - no need for a UPS (Uninterruptible Power Supply) unless you need to play the game during power outages.
Instead, I suggest installing a TVSS (Transient Voltage Surge Suppressor) receptacle. This device can protect an entire string of outlets if wired properly by daisy-chaining (or enslaving) all receptacles in the string to the TVSS located at the head of the outlet chain. Or it can simply be a point-of-use device - your choice based upon your needs.
A 20 amp circuit is rated to deliver 80% of its name-plate rating of 20 amps continuously. In other words, if the circuit runs 24/7 you can load the circuit up to 16 amps without problems. This equals approximately 8 machines allowed on a circuit. Using the 80% rule will help prevent problems and your system will be less stressed under load.