Will a 420 watts power supply be enough for my gts250 gpu ?

Solution
It should be ok. The GT250 can draw 150 watts at max load.
If your paring it with a core 2 duo 3.0 like a e8400 they can pull a round 65 watts at max load.
If your paring it with a core 2 quad or an AMD phenom they can pull around 100.

So figure 150 for the GPU
100 for the CPU
50 for the motherboard, ram, drives, fans,
Total draw will be around 300.
 
For a system using a single GeForce GTS 250 graphics card NVIDIA specifies a minimum of a 450 Watt or greater system power supply that has a maximum combined +12 Volt continuous current rating of 24 Amps or greater and that has at least one 6-pin PCI Express supplementary power connector.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

What is the brand and model number of the 420 Watt power supply unit?
 

Its a thermal master 420 watts psu which comes with a cooler master elite 370 casing
 
That PSU sounds sketchy. What are the 12volt amperage ratings on the side of the PSU, or the exact model?
If you figure your computer will draw 300 watts, at 12 volts that's a draw of 25 amps. Figure 300watts / 12volts = 25 amps. If the rating is 24-25amps or higher I would go for it. If its lower there is a very good chance that the PSU will burn out during a gaming session.
 


That Thermal Master 420 Watt power supply unit only has a maximum combined +12 Volt continuous current rating of 16 Amps. That's grossly insufficient to power a system with a single GeForce GTS 250.

The GeForce GTS 250 itself can draw up to 12 Amps from the +12 Volt rail under a typical 3D graphics load. That only leaves you with 4 Amps to power the rest of the components like the CPU, motherboard, hard disk drive(s), optical drive(s), cooling fans, etc. It won't work.
 
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