A gaming computer has a large number of electronic and mechanical components like CPU, graphics card, memory, RAM, SSD, fans which require a reliable electrical power supply. Hence it is important to ensure that an appropriate power supply is selected, which provides enough power to all the components which are used, else the performance of the computer will be adversely affected. It is also advisable to check the dimensions of the power supply to ensure that it is compatible with the cabinet which is being used. Usually for a ATX motherboard, space is not a problem, however for smaller motherboards of size mATX, miATX, dimensions could be a problem.

Before selecting the power supply, it is advisable to calculate the approximate rating of the power supply required based on the components which are being used. The graphics card, CPU and memory consume the largest amount of power, and the power consumption is usually mentioned in the manufacturer specifications or data sheets. Many of the component and motherboard manufacturers like Cooler Master, Seasonic and MSI have online calculators where the user can specify the components selected to get the rating of the power supply required. However, it should be noted that most of these online calculators will overestimate the amount of power supply required.

The power supply units (abbreviated as PSU) are labelled 80 plus if their efficiency is more than 80 % under 20%, 50% and 100% load conditions. They are further rated as bronze, silver, gold, titanium and platinum, depending on their efficiency, with bronze PSUs cheaper and less efficient than gold and platinum PSUs. It should be noted that avid gamers may prefer to purchase a gold PSU though it is more expensive, since they will save money in their power supply bills. Earlier gaming computers were consuming a lot of power, however since NVidia introduced high efficiency graphic cards, the power consumption has reduced to a great extent.

Typically, most of the PSU are rated for an input voltage of 240 VAC, 4 Amperes, 50-60 Hz. The manufacturer will usually also specify the current output at different voltages like 3.3 V, 5V, 12 V, 5V serial bus, -12 V. Most of the power supplies are rated for continuous power supply output instead of peak power output. The power supply usually will include over voltage protection, under voltage protection, short circuit protection, overcurrent protection and overpower protection. A fuse is usually included in the power supply to protect against spikes in the current and it can be replaced if required.

Bitfinex, Seasonic, EVGA, Corsair, are some of the more popular brands of power supplies which are available for sale. Though Corsair is the more popular brand for computer hardware, in the last few years EVGA offers more inexpensive PSUs and has become the more popular brand for online sales. Unless multiple graphics cards and high end components are being used, a power supply with less than 1000 W output like the Corsair RM 750X is adequate for most gaming computers.

For budget gaming computers, a power supply rated at 500 W like the EVGA 500 W1 with 80 plus white efficiency is adequate since it is fairly inexpensive, costing approximately $37 at a leading online retailer. The EVGA 500 B1 with 80 plus bronze efficiency is another PSU which is also suitable for budget gaming computers costing around $44. However only a three-year warranty is offered for EVGA PSUs which can be extended to five years in some cases.

For most gaming computers used with the latest games available, the Corsair RM 750X with a rated power output of 750 W is adequate. The 80 plus gold rated PSU has a zero RPM mode, for low and medium loads. The fan is automatically switched off when less power supply is required to reduce noise, and even at higher loads the noise produced is less. This power supply is good value for money since Corsair offers a ten-year warranty on the power supply and it uses high quality Japanese capacitors. The cables used are modular so it is easy to connect and disconnect to other parts of the motherboard.

So based on the budget, energy efficiency, noise levels, warranty offered,  a suitable power supply for a gaming computer should be selected.