Quoted from Isochronic_Frost:

Here’s two old threads for reference, a ton of people throw nonsense around without a clue.
https://pinside.com/pinball/forum/topic/whats-the-most-amount-of-pinballs-youve-had-on-a-breaker#post-4066012
https://pinside.com/pinball/forum/topic/what-size-breaker-would-suffice-for-5-6-modern-pins-
At my arcade we ran over 9 machines on one 20 amp breaker for over a year before the breaker finally gave up the ghost and literally melted. And it turned out it didn’t melt because of the load, it melted because one power supply went bad in one of the games (it was a mix of pins and arcade machine with CRTs) and it would draw insane currents.
The bad power supply was cooking itself and cooked the breaker too.
People mention it’s “safe” to put 5 to 6 games on a 20 amp, but a 20amp is rated for way way way above that. They have tons of safety built into the electrical code to be conservative because they already factor in that some guy will hook up 4 salamanders and the house needs to be built in a way that careless and clueless homeowners won’t accidentally burn it down.
Here is an AWESOME Facebook post in the operators group. I can copy paste it for you.
“ I am an Electrical Contractor by trade so I spend a lot of time with these numbers. A non LED pin draws roughly 250w while playing. 200w in attract mode. A 20A circuit at 120v provides 2,400w of power. If all games are being played at once you can have 9 pins on one 20A circuit. 7 pins on a 15A circuit. Games with LED lighting draw roughly 100w so you can do that math as well.”
https://m.facebook.com/story/graphql_permalink/?graphql_id=UzpfSTEwMjE3NDE1NDA6Vks6MjczODYzMjY2OTc1NDYyNw%3D%3D