Powering Your PC: Truths and Misconceptions
A Guide To Power Supplies

Power Supply Weight:

Some people consider the weight of a power supply to be an important factor, if it weighs more then it must be better, right? Wrong! Weight has very little to do with the quality of a power supply. That methodology would be no better than saying the color of a car determines how fast it can go (which we all know the two are completely non-related).

If you subtract the weight of the all the wires, along with the PSU chassis, there isn't much left. The bulk of the weight inside a power supply is the transformer(s) because they are nothing more than big spools of copper wire. Also the heatsinks (which has transistors & diodes mounted to them) contribute some weight, however they are aluminum which is a light-weight material. No two power supplies are designed alike, so the components inside (which all naturally weight different amounts) can vary drastically.

Lets focus on the field transistor (device that switches the power), it weight practically nothing. The size is a standard dimension, so in reality one of a hundred different models could be used. The primary difference is the specifications / ratings of the device, which is all driven by cost. A cheap transistor might generate more heat (thus require a larger heatsink) and have a lower power rating than a similar, but more expensive higher-quality transistor (which would require a smaller heatsink). Similar principle for the diodes that require a heatsink.

Other components like capacitors, resistors, and chokes don't require any heatsinks, and are all relatively light weight. Quality of these components can only be determined by its brand and specifications, not the weight.

Cooling is another trick some PSU manufacturers use to shave off some weight or use cheaper components. By forcing more air through the power supply, the heat can be dissipated faster and the components can be kept cooler. The down-side to this is an increase in noise from the fans.

It's all a balancing act between cost, efficiency, and capacity. Naturally it costs more for higher-quality solid-state components than it does for a piece of aluminum or a fan. Generally speaking, the cheaper the components, the lower the efficiency, the more heat, the more cooling required (in the form of a heatsink and/or fan).

A few things you can look at are the cooling fans, the gauge of the wiring, and the connectors. The more fans and the higher the RPM means that some serious forced air cooling is going on, not always a good thing (for reasons mentioned above). Another way to save some money is that some manufacturers will use a thinner gauge wire (the higher the number, the thinner the wire). 16 AWG is the most common on the main 24pin power connector, and 18 AWG for all peripheral cables. Lastly, the connectors can be either tin-plated or gold-plated. Obviously the gold-plated connectors are superior, and come at a premium cost, so you usually won't see them on cheap power supplies. Most motherboards & peripherals only have tin plated connectors, so really this is a personal decision as to the level of importance.