Hi, I currently have an EVGA G3 850 installed in my system but I just bought an EVGA P2 1200 as I’m upgrading motherboard and CPU. I was wondering if I can keep the existing power wires and reconnect them to the new PSU and motherboard so I don’t have to do the whole cable management again from scratch? Both PSU are Unites States versions in terms of AC voltage.

See: Which EVGA Modular Cables are compatible with my PSU? in the EVGA FAQs

Yes, they are compatible/interchangeable..Carry on.

Thanks. What about wattage rating? I understand the pin configuration is the same, but in the link you sent different models are for maximum wattage allowed. Could that be possible that cables that shipped with the G3 850, although the pins configuration is the same as the P2, cannot tolerate 1200 watts delivered by the P2 1200?

In the Compatibility tab on the 1200 P2 Product Page it says the cable sets like 100-CK-1300-B9 (and others) are compatible with 450W - 1600W units..Same with the cables sets on the 850 G3 Product Page..If in doubt you can always Contact EVGA Customer Service about it.