GTX 780 Classified Hydro Copper / 780 Classified models:
Minimum of a 600 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 42 amps)
Two (2) available 8 pin PCI-E power connectors

GTX 780Ti/780/770 models:
Minimum of a 600 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 42 amps)
An available 6 pin PCI-E and 8 pin PCI-E power connector

GTX 760:
Minimum of a 500 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 30 amps)
An available 6 pin PCI-E and 8 pin PCI-E power connector

GTX Titan:
Minimum of a 600 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 38 amps)
Two (2) available 8 pin PCI-E power connectors

GTX 690/690 Signature:
Minimum of a 650 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 38 amps)
Two (2) available 8 pin PCI-E power connectors

GTX 680 Classified:
Minimum of a 550 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 38 amps)
Two (2) available 8 pin PCI-E power connectors
 
GTX 680 SC Signature/FTW/Hydro Copper:
Minimum of a 550 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 38 amps)
An available 6 pin PCI-E and 8 pin PCI-E power connector

GTX 680 / 680 SC:
Minimum of a 550 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 38 amps)
Two (2) available 6 pin PCI-E power connectors

GTX 670 (All):
Minimum of a 500 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 30 amps)
Two (2) available 6 pin PCI-E power connectors

GTX 660 Ti (All):
Minimum of a 450 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 24 amps)
Two (2) available 6 pin PCI-E power connectors

GTX 660 (All) /  650Ti Boost:
Minimum of a 450 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 24 amps)
An available 6 pin PCI-E power connector

GTX 650Ti / 650:
Minimum of a 400 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 20 amps)
An available 6 pin PCI-E power connector

GTX 640 / 630:
Minimum of a 350 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 20 amps)
No PCI-E power connector needed

GTX 620:
Minimum of a 350 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 18 amps)
No PCI-E power connector needed

GTX 610:
Minimum of a 300 Watt power supply
(Minimum recommended power supply with +12 Volt current rating of 16 amps)
No PCI-E power connector needed