!!! IMPORTANT !!!
Check with your Power Company and/or a Locally Licensed Electrical Contractor for limitations of home power availability. They might require an electrical architect to evaluate electricity needs and advise the Power Company on adding another line to the house.
!!! IMPORTANT !!!

One 15/20 AMP Breaker or Circuit is for 3 PC’s.
1 PC = 1 tower & 1 monitor

Formula: Amps x Volts = Watts
15 x 120 = 1,800
20 x 120 = 2,400

1,800 Watts / 3 PC’s = 600 Watts per PC
2,400 Watts / 3 PC’s – 800 Watts per PC

NOTE: You might be thinking, 600 Watts per PC, but my PC has a 750 Watt PSU (Power Supply Unit) in it, what if there are 3 PC’s with 750 Watt PSU’s in them?

PC Components rate their hardware at MAX power consumption which also includes a “flux” factor.

A GPU might say it requires a 650Watt PSU and that is for max usage to include all the other legs on the power supply being used for hard drives, optical drives, fans, lights, flux capacitors, ect. Most PC’s today have m.2 storage that runs off the motherboard power, a 2.5″ SSD (2 Watts), and a GPU. Air coolers run off the Motherboard mostly and AIO’s have their own power for the fans.
Basically, you’re not using what you think you’re using, but it’s close.

I recommend putting “higher end” PC’s with custom cooling loops, big pumps and multiple GPU’s that mine for bit coin when not being used on their own circuit or 2 PC’s per circuit.

Something I did for my kids and their friends; If they wanted to participate in the LAN they would need to initially bring their own PC from home. We would then open it up, I would teach them about it and maybe troubleshoot issues it had. Then I/we would make a trip to Fry’s Electronics (RIP) and buy parts for a new PC for them to build. (Frys gave me an awesome 30% off for doing this!) Each build though got a Corsair AX860 ATX PSU for effiency, I controlled what power they used, and to future proof the build for them. I also purchased at first Intel “K” i7’s and EVGA 970/1070 70 series cards on MSI “Z” motherboards, but eventually moved to Intel “Non-K” CPU’s on MITX motherboards and Samsung 2.5″ and M.2 SSD’s to further control the power draw. If they could build the PC (everyone else could help) and it booted, they got to keep the PC (without needing to “owe” me back in anyway). To this day, 10+ years later, I’m still hearing about these PC’s running and sometimes getting them through school!
Thank you to all the people from Fry’s! (This would not have been possible without you. Much Luv!)

!!! IMPORTANT !!!
Check with your Power Company and/or a Locally Licensed Electrical Contractor for limitations of home power availability. They might require an electrical architect to evaluate electricity needs and advise the Power Company on adding another line to the house.
!!! IMPORTANT !!!

2 car garage = 20 PC’s
1 car garage = 10 PC’s
20 PC’s = 36,000 Watts
20 PC’s = 7 Circuits (plan to add extra for networking, server(s), HVAC, peripherals like printers and tools.)
Consider installing an HVAC unit for the Garage. (2 car garage, 2 ton unit)
After checking with Power Company or Licensed Electrical Contractor, it is possible to add a sub panel off the main breaker panel to supply additional circuits.
At first you might run ethernet cable all over the floor with lots of extension cords. Try to keep the ethernet and power extension cords a foot or more apart from each other to prevent as much interference as possible.
Getting electricity to the 10 people sitting in the center tables of your 20 person LAN in a 2 car garage can be a challenge. I did it by putting extra outlets in the ceiling to plug into. (You can also put your extra LAN Drops by these ceiling outlets too.)

!!! IMPORTANT !!!
Check with your Power Company and/or a Locally Licensed Electrical Contractor for limitations of home power availability. They might require an electrical architect to evaluate electricity needs and advise the Power Company on adding another line to the house.
!!! IMPORTANT !!!