PSU Amps

What is am amp? An amp is an ampere, which is a measure of electrical current. Imagine electricity as water in a pipe. Voltage is the pressure being applied to the pipe, while current is the amount of water in the pipe. Voltage "pushes" the water through the pipe and current is how much water actually arrives at the location.

So they have voltage and current. What about power? Power is voltage times current.

Current * Voltage = Power

Amps * Volts = Watts

VI=P

Computer power supplies deliver power at multiple different voltages, to be used by different devices. There is +12V, +5V, +3.3V, +5V standby, and -12V.

These voltages stay constant. The amount of current varies to meet the requirements of the computer the PSU is connected to. A power supply is rated on each voltage rail to supply up to the rated current. So if a technique is rated to provide 20A on the +12V, the PSU can safely provide up to 20A on that rail (usually the over current protection will shut in around 22-25A).

Now, in the event you were being attentive above you ought to have noticed that the +12V rail powers much over the other rails do, including heavy hitters like the CPU and GPU. This has been the case since the year 2000 when the ATX12V specification was introduced, replacing the elderly ATX specification; and the ATX12V has since been refined further with ATX12V 2.x.

So, all modern systems draw all of their power from the +12V rail, usually 75%-95% depending on the system. So naturally you ought to expect power supplies to deliver 75%-95% of their power on the +12V rail as well.

And when I recommend a power supply, it will have 80%+ of its power available on the +12V rail.

If the total +12V capacity is less than 80% of the power supply's total wattage rating then it ought to be thought about to have a lower wattage than what it is labeled as. So you take the total +12V capacity and divide by 80% (0.80) and that is the "real" wattage with regards to modern systems. So in the event you have a 500W power supply with 350W on the +12V rail then it ought to be thought about to be a 430W power supply, since 350/0.8 = 437.5 (feel free to round up or down a bit; try to stay within 10W).

Having a +12V current rating that makes up over 80% of the PSU's wattage rating does not make it a higher wattage power supply. This is because the wattage will usually be limited by some other part (usually the primary side parts) than the rectifiers that produce +12V current.

But how do you get the total +12V capacity? It is usually labeled right on the power supply. However, some power supplies don't list total capacity in watts, only the current ratings. If the power supply is a single rail then you multiply the current rating times 12V to get the wattage. But what if a PSU has multiple +12V rails? You don't add all of them together. You require to discover a combined +12V wattage rating, and if it doesn't list it then there is no way to know without either finding the OEM version of that PSU or finding a professional review to tell you its approximate capabilities.

Taking a look at +12V amperage will tell you what a power supply's actual capabilities are. But at the finish of the day, with quality power supplies (such as I will recommend), amperage is NOT more important that wattage. Taking a look at the current ratings is basically a device to tell you more about a power supply. Which PSU has a bigger amperage rating is not the way you ought to pick what PSU you pick or declare "better".