Your desktop’s power supply plays an important role in your system. It converts the AC power from your home or office into the Direct Current that your PC needs to operate, then distributes that power to each component. That clean, consistent power is step one to building a reliable system. So needless to say, it’s pretty mission critical. But what does an individual Power Supply’s wattage or its efficiency rating even mean? And how much wattage do you need in your next dream PC?
Wattage and Efficiency
To start, power supplies have two basic ratings to be concerned with – wattage and efficiency. The wattage is simple; it’s the maximum amount of power the supply can output when under a 100% load. So a 600W power supply can distribute UP TO 600 watts to the PC’s components.
The efficiency rating is how well (or how efficiently) it converts the AC power to DC, or to look at it the other way, how much power it wastes during that conversion. For example, a Bronze Rated power supply, which by definition must be at minimum 82% efficient at full load (with higher efficiency at lower loads), will output 82% of the inputted AC power to DC, losing 18% of the original wattage to heat. That means that a 600W Bronze Certified PSU with its 82% efficiency will draw about 730W in order to output the 600W.** Along with being greener, higher efficiency power supplies like Bronze, Gold, and Platinum also tend to last longer because a less severe heating/cooling cycle.
**Remember, that’s only under full load – a PSU will only draw what it needs to.
Matching Wattage and Efficiency to Your Custom Components
A critical element to the configuration of your PC is ensuring the PSU you choose is robust enough to output the power needed to run the components that you’ve selected, with a bit of headroom to spare. Consistently maxing out your power supply is not the best recipe for system longevity, after all, not to mention the fact that PSU’s generally run at optimal efficiency at 70%ish load. Here is a very rough list of the estimated power consumption of your vital PC components, though obviously these numbers will vary for each specific component.
- Low/Mid-range graphics (like GTX 1660) ~165-200W
- High-end graphics (like RTX 3080) ~350W
- Mechanical Hard drives ~9W each
- Solid State Hard Drives ~3W each
- Intel/AMD Consumer CPU (i5-10600 or Ryzen 5 5600X) ~75-125W
- Intel/AMD Pro CPU (Intel Xeon or AMD Threadripper) ~140-200W+
- Motherboard ~30-80W
- RAM ~3W per stick
- Optical Drives ~25W
As you can see, the graphics card (or cards) will be the biggest power draw in your PC with some top end graphics like RTX 3000 series pulling 350W+ each while under load, although significantly less at idle (or more if overclocked). But even with several hard drives and a decent Intel or AMD CPU, a 750W power supply is sufficient for most single GPU configurations. For multi-GPU systems, we typically recommend at least a 1000W or more. If you’re unsure of the best PSU for your config, we recommend using an online PSU calculator.
One last note – when choosing a power supply, it’s important to select something that will not just meet your current needs, but also something that will suit you for any planned or possible upgrades. Plan ahead!