How an expensive PC power supply is different from a cheap one

Many users buy a computer power supply “on change”, because it does not affect the performance of the PC. At the same time, attention is paid only to the power indicated in the characteristics and low cost. But cheap and expensive power supplies are very different in a number of parameters.

The choice of a power supply unit is complicated by the fact that there are dozens of models on the market with the same, at first glance, characteristics, but completely different prices. If we open the catalog of power supplies , then first of all we will see their power, a set of connectors and a price. But most of all the characteristics of interest to users – reliability, real service life, voltage stability and noise level – are difficult to learn from the description.

For this reason, a novice user often makes the mistake of deciding to save money and buys a cheap power supply for a productive computer. But a high-quality power supply is a guarantee of stable and reliable computer operation and you should not save on it, and what you can get by choosing a more expensive model, you will learn from our blog.

Declared and real power

The power supply capacity is usually declared as the sum of the capacities of all supply lines. Here you can see the first difference between cheap and expensive models. If we look at the characteristics of an inexpensive power supply indicated on its sticker, we will see that a 450 watt model can deliver 120 watts on 3.3 and 5 V lines, which are practically unloaded in modern PCs, and only 360 on the most important 12 V line. watt.

That is, an inexpensive power supply will not be able to provide the power that is indicated in its name. For high-quality products, almost all the power is available on the 12V line, so an expensive power supply unit, even with a small power, will be better than a cheap one with steeper written characteristics.

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Be quiet! Power supply Pure Power 11 350W [BN291]
4 299 *
But the main problem with cheap power supplies is that they usually do not deliver the declared power . If you look at the tests of inexpensive models with maximum load, you can see that they overheat, have high voltage drops, go into protection or simply burn out. The budgetary element base will not provide the full power output for a long time, but it is not designed to power powerful computers either. They are intended for office PCs or entry-level gaming machines.

Expensive high-quality power supplies not only can withstand the maximum load specified in their characteristics for a long time, but are even able to work with its excess. They also have a wider range of protections than in cheap devices: OCP and OPP against overload, OVP and UVP against over and under voltage, SCP against short circuit and OTP against overheating. It is very important not only the availability of protections, but also the quality of their implementation, which is given much more attention in expensive devices.

Efficiency and 80 PLUS Certification

The difference between cheap and expensive power supplies is especially noticeable when you compare their efficiency. The efficiency of inexpensive models can reach as little as 75% in various modes of operation, that is, 25% of the power received from the outlet turns into useless heat, heating the insides of the device. More expensive models have efficiency certificates ranging from 80 PLUS, which requires at least 80% energy efficiency when the PSU is loaded at 50%, and up to 80 PLUS Titanium, which requires 94–95% energy efficiency depending on the supply voltage.

Power supplies certified under the 80 PLUS program can operate in a wide range of mains voltages – from 100 to 240 V, which ensures stable operation of the PC and will be useful in case of voltage fluctuations in the network. Some time ago, some models began to be certified according to the 80 PLUS 230V EU Internal standard only for the mains voltage of 230 V, which has more stringent energy efficiency requirements starting from 85%.


The high efficiency of the power supply that meets the 80 PLUS Gold standards and above can only be achieved with the help of high quality electronic components and modern circuitry solutions, therefore, the presence of such standards indicates the quality of the device. And if the energy saving even when using a PSU in a powerful gaming computer is not very impressive, then the opportunity to get a high-quality device with low heating is definitely worth the surcharge.

Reliability and long warranty period

The power supply , like most other electronic devices, wears out over time. The weakest link among its electronic components is electrolytic capacitors filled with liquid electrolyte, which over time decrease their capacity, dry out or swell, losing electrolyte. The process of degradation of capacitors is especially accelerated with strong heating of the power supply, and this is common with a heavy load of a budget model with.

In expensive models, high-quality capacitors are used that can work at high temperatures for much longer than the capacitors of little-known Chinese firms, which are enough for two or three years at best. Medium quality capacitors are manufactured by Teapo, Jamicon, OST, Samwha, Samxon, ELNA, Vishay, CapXon, Hitachi, Hitano. In top-end power supplies, for which manufacturers give a five, seven or even 10 year warranty, you can find United Chemi-Con, Sanyo, Nippon Chemi-Con, Panasonic, Rubycon, Nichicon, Epcos, Fujitsu capacitors.


But sometimes manufacturers are cunning: when you come across the inscription “Japanese capacitors”, you can find only a couple of such high-voltage components inside the device. But the long warranty period is a much more weighty argument in support of the fact that the manufacturer used the most reliable capacitors in the power supply and is confident in their comfortable temperature mode of operation. For this, circuitry solutions are additionally used, which make it possible to partially use much more reliable solid-state capacitors in the power supply unit.

Noise level, heating, semi-passive and passive modes of operation

Affects the life of the power supply and the quality of the fan used for cooling. In budget models, sliding bearing fans are widely used, which, after working for three to four years, wear out and begin to make noise . In expensive models, high-quality long-life fans with hydrodynamic bearings and rolling bearings are used.

Power supplies with high efficiency and efficient heat sinks allow much lower fan speeds to be used, which significantly reduces noise levels.


The use of high-quality transistors with low RDS (on) (Drain to Source On Resistance) has a beneficial effect on the temperatures of the power supply. These transistors have improved performance and low resistance when switching states, which allows for increased efficiency and use of small heat sinks due to reduced heating.


Semi-passive cooling mode has become popular in modern expensive models, in which the fan does not rotate at all until a certain temperature or load is reached. This allows you to create a computer with zero noise under light load.
The semi-passive cooling mode makes even more serious demands on the quality of the components and circuitry of the power supply, but the most stringent requirements are for the fully passive mode, which is available only in the most expensive and high-quality models.

Seasonic PRIME Fanless TX-700 Power Supply [SSR-700TL] 30 499 *
High voltage stability and low ripple at maximum power

The ATX standard allows 5% deviation of the main supply voltages of the power supply, which for a voltage of 12 V is a fairly wide range from 11.4 to 12.6 V. But for budget power supplies, keeping the voltage within these limits becomes a very difficult task even at 80% load. Even inexpensive 550-watt devices from well-known companies often cannot provide stable voltages at a load of only 400-450 watts.

It is unpleasant that in power supplies with outdated circuitry and group voltage stabilization, with a drop in one of the voltages, the others also grow, often going beyond the ATX standards and risking damaging the components. In expensive models, individual stabilization of voltage lines using DC-DC converters is used and even at maximum load they keep within normal limits.


All computer power supplies are switched-mode, which is why ripples inevitably appear in the output voltages. They are clearly visible if you connect the device connectors to the oscilloscope. The standard defined by the ATX12V Power Supply Design Guide requires that the ripple of the output voltages at maximum load does not exceed 50 mV for +5 V and +3.3 V rails and 120 mV for + 12V rails. High ripple affects stability. operation of the computer, give hints to sound cards, cause malfunctions in hard drives that are sensitive to high-quality power supply.


Many budget devices hardly fit into the ripple norms even when they are new, and after a couple of years, when the degradation of inexpensive capacitors begins, ripple can increase sharply, especially at high load.

In expensive models, much more attention is paid to the fight against pulsations and, as a rule, they do not go beyond the norm, even at extreme loads. And the use of quality capacitors ensures that they remain normal even after several years of operation.

A set of cables and connectors, modularity, length and cross-section of wires

A noticeable difference in the cable systems of expensive and cheap PSUs. If budget models use short wires without braiding with a minimum of necessary connectors, then expensive ones can boast of long, convenient for laying behind the back wall of the PC case, wires that are covered with braid or made in the form of flat loops. Such wires do not spoil the appearance of the assembly and allow you to create a beautiful gaming computer.


Many expensive power supplies are modular. You can easily detach unnecessary wires from them. This greatly simplifies the assembly of the PC and has a positive effect on its aesthetics. Buying an expensive power supply unit, you will not face a problem when there are not enough connectors for connecting video cards, powering a processor or drives. Even on 550 watt models, the connectors are enough to create a powerful PC with a powerful graphics card and an overclocked processor.


Corsair RM550x Power Supply [CP-9020197-EU]
11 499 *
An important parameter is the cross-section of the current-carrying conductor of the wires, which is marked with AWG. In budget models, thin 20 AWG wires are often used, which can get very hot, powering voracious components. Manufacturers insure themselves in expensive power supplies and use 18 AWG wires, and 16 AWG for powering video cards and processors in powerful models.


The quality of the connectors is also important, because if they loosen, giving incomplete contact, and in your PC there may be a risk of wires melting, sparking and even fire. So, not only the thickness of the metal in the connectors is important, which they do not save on in expensive models, but also the durability of the plastic from which their cases are made.

Additional functions: backlight, control and monitoring

A modern gaming PC cannot be imagined without component backlighting, which is why it is also used in power supplies. RGB lighting allows you to organically fit the power supply into your system by choosing the right color. Designers work on expensive models who manage to make a beautiful device out of an ordinary metal box that can decorate any assembly.

Advanced power supplies have long used microcircuits that track the parameters of input and output voltages, temperature, power consumption and fan speed. And on some models, the developers have provided for the output of these parameters via the USB interface and their reading by a special program that allows you to monitor all the parameters of the power supply.


This feature turned out to be very useful for computer enthusiasts doing component reviews. With its help, you can accurately calculate how much a processor or video card consumes, abandoning primitive wattmeters. On especially advanced models, LCD displays appeared , displaying information about the operation of the device. Some models allow the fan, single or split power bus modes to be configured via the software interface with the OCP setting for overcurrent protection.


As you can see, the differences between expensive and cheap power supplies are not limited to power, reliability, and voltage stability. Their aesthetics, ease of use, noise characteristics, durability and warranty period differ. Of course, cheap power supplies have their own niche of use: when assembling an inexpensive office “typewriter” with modest power consumption, you should take a closer look at them. But building a gaming PC and hoping that it will serve you for several years is definitely not worth saving on a power supply.