Power Supplies

by | Jul 19, 2022

So you finally took the plunge and decided to build a gaming PC, you’ve ordered the CPU and GPU and a motherboard and cool RGB fans as well. You’ve spent hours if not days or weeks pouring over online forums and YouTube reviews for every single component and every time you finally chose one you felt good inside. Then you remembered your computer will need a power supply and you spent five minutes on Newegg, listed the items by Lowest First and chose the first one that had a good wattage per dollar ratio at less than $50 dollars. Well today’s article will deal with power supplies and hopefully by the end you will be able to make a better choice than the example above (or should you?).

First off, what exactly is a power supply? In broad terms, a power supply is a device which supplies electric power to a load (in our case, a computer and the components connected to it). A power supply will generally take in current and give out a well regulated constant voltage and current. In our case, PC power supplies are a type of AC to DC power converters (they take in 120VAC and give out the DC voltages that computer components need). As for the types of voltages that they put out these include: Ground, +3.3V, ±5V, ±12V (all DC of course). So what exactly are all those different voltages (or rails) used for? The 3.3V is used mostly by the different chipsets on a motherboard (think chips that deal with data transfer and such), your RAM also makes use of this voltage, PCI cards also use this voltage (though not many PCI cards exist anymore) as well as a plethora of miscellaneous chips. The five volt rail is used mostly by disk drives (or SSDs), certain PCI cards, voltage regulators and several other miscellaneous chips. The twelve volt rail is use mostly by motors (think floppy and DVD drives) as well as a couple of voltage regulators. Those that looked closely might have noticed that power supplies also provide a -5V rail and a -12V rail, what gives? Well they do have uses but are mostly still included in today’s power supplies so that they can be certified truly backwards compatible with older systems. The -5V rail used to be supplied to the ISA bus for use in ISA cards but those are pretty rare to find in newer systems. The -12V rail does have a much more important (but almost singular) role in that it helps the LAN adapters works properly (LAN adapters require +12 and -12V to function).

Before we begin discussing any further let us talk a little bit about how power is measured. Electrical power is measured in Watts and is defined as the current flow of one ampere with a voltage of one volt (if a load requires 10V to operate and draws 5amps then it is using 50 watts of power). Graphic cards today for example may draw anywhere from 20 watts (at idle) to up to 300 watts when under extreme use (such as gaming); and in absolute crazy circumstances may draw as much as 400W at their absolute peak (for fractions of a second however). This brings us to another detail, namely, peak versus continuous power draw. Essentially, continuous power is the amount of power that a particular power supply will be able to supply without breaking down or shutting down. Peak power will be the maximum amount of power that a power supply can supply for split seconds at a time only. When shopping for a power supply make sure that a continuous power rating is listed; don’t be fooled by a peak power rating since you cannot expect the power supply to function at that rating without breaking down eventually (or worse, taking other components with it).

At this point we have finished discussing some of the basic elements of power supplies, so now the question is how do you choose one? The first step we must take is figuring out how much power the computer as a whole will demand when it is operating. This task is rather easy since we simply have to add the power draw from each of our components: the motherboard, the CPU, the graphics card and your number of hard drives. Finding the max power draw for each of these components is as simple as typing their model number on a search engine and looking at their user manual. For the most part the elements above will be found in every single computer but your computer might be different, for example, you might have 2 or more graphics cards or perhaps a sound card or a dozen hard drives. Make sure that you look up every component that will be plugged into the motherboard and add up their power draws then add an additional 10% extra wattage to err on the safe side of things and voila you’re done most of the work in choosing a power supply unit at this point. We recommend adding that 10% extra wattage because of a couple of reasons. First, you don’t want your system to ever try to draw more than the power supply can handle otherwise you will experience weird crashes or slowdowns. Second, most component user manuals will list the continuous power draws but the peak power draws might be a little bit higher so having that extra wattage can compensate for that. Lastly, having a little extra wiggle room can be helpful for upgrading your PC down the line. For example, if your computer draws 500W and you’re power supply can supply up to 550W then you could add an extra hard drive or two without going over the 550W limit. Whereas if you had gone with a 500W power supply adding any extra components would be out of the question since you would now be over your power supply’s 500W limit.

Well, if 10% extra wattage is a good rule of thumb why not just go all out and get an extra beef power supply say 1000 plus watts? Well, there are a couple of reasons why you might or might not want to go that route. First let us talk about the negatives of having a power supply too large for your system (going by the same 500W from our previous examples). The most obvious reason why you wouldn’t want it is because they are much more expensive as the wattage rises above 750W or so. Next is, well, actually that is about it. There’s really no other negative about having huge power supplies other than being expensive and never realistically using their full potential. “Wait,” you say, “what about efficiency?” For the most part you don’t have to worry about that. It used to be that decades ago power supplies that were too large, say 1000W, when run at wattages far lower than their peak (say, 25% or less) they would suffer from huge efficiency losses (in other words, a 1000W supply supplying 250W would waste far more electricity than a 300W supplying the same 250W). However, that is most certainly not true anymore, even bottom of the line (but still from a reputable company) power supplies will exhibit efficiency curves that are essentially straight lines all above 90+%. Ok so why would you get a power supply with huge power ratings? Well, one good example is noise. Huge power supplies now a days will have a fan-less mode when they are run at a certain percentage of their max capacity since they are hardly breaking a sweat (for example, many 1000+ watt power supplies have fan-less modes when running below 25%-35%). That alone can be a deciding factor for many PC enthusiasts. Another reason why is something that we already mentioned and that is upgradeability. Most hardcore gaming computers now a days will top out at around 500W but having that 1000W limit available to you means you could add a second graphics card, several more hard drives, even severe over clocking of your CPU and still be within your power supply’s limits; comfortably at that. The last reason for choosing a huge power supply is a little more subjective but basically it is creature comforts. When you choose power supplies with such high wattage ratings they tend to be a company’s flagship models and hence they include many features that smaller wattage power supplies might not have. Some of these features could include: ECO mode, active wattage readings via a tiny screen display, RGB lighting and modular cabling to name a couple.

The last advice we can give the readers will be to always buy a power supply from a trusted company (Corsair, EVGA, and Sea Sonic to name a few). There are many reasons why you would want a name brand over some cheap power supply that you can buy on eBay. The most important one however, is that name brand power supplies will carry all the safety certifications and technology that a good power supply should have. For example, any name brand power supply will include the following: short circuit protection (in case a short appears the power supply won’t supply the maximum amount of power that it can to the entire computer thus killing several components instantly), overload protection (if your components’ power requirements exceed the power supply’s rating then the supply will shut off to prevent damage to itself), overvoltage protection (self explanatory, you can expect nice and steady DC voltages), under voltage protection (not as dangerous as overvoltage but annoying because it can cause random crashes or shutdowns) and over temperature protection (will shut itself off correctly if it is reaching dangerous temperatures). All of these features are standard on even the cheapest models from trusted power supply manufacturers but often times left out in off brand power supplies found on eBay or sketchy websites. The peace of mind that these features bring is more than worth the extra $30-40 that you might spend on a power supply from a reputable manufacturer. Not only that, but you can think of a power supply about doing more than just powering your computer: it is protecting the components inside as well.

Lastly, while shopping for a power supply you might encounter that some may have an “80 Plus” certification followed by a name of a precious metal that ranges from Bronze all the way to Titanium. 80 Plus is a certification program that promotes the efficient use of electricity. Basically, if a power supply is sufficiently efficient it can receive an 80+ Bronze rating or better. You will also quickly notice that power supplies with the same wattage capacity but different 80+ ratings will vary wildly in price (a 650W 80+ Bronze will be far cheaper than a 650W 80+ Titanium). However, you shouldn’t base your decision on these ratings alone unless you want to do your part for the environment or your country of residence requires a certain efficiency rating for home use. When it comes down to it the Titanium rated power supply might save you a couple of cents a month (maybe a dollar or two a year) in electricity over the less efficient Bronze rated power supplies. The truth might be a little underwhelming but it basically boils down to the fact that 80+ ratings are tested at a power supply’s upper wattage capabilities where like we mentioned before almost any modern power supply will have essentially flat efficiency curves in the 90s of percent.

So there you have it, a basic overview of what power supplies do in a system and what you should look out for when choosing one of your own. If you have any more questions or would like recommendations then swing by The PC Portal where our technicians can give you a helping hand or point you in the right direction for your next sweet gaming rig. Do you have any topics or questions that you would like answered and talked about? Let us know. Until next time, have a good day!