How to pick the right PSU wattage for your Gaming PC!

Whether you’re planning on building a new gaming PC and need to pick the right power supply for it, or you’re upgrading your GPU and you want to make sure it’ll actually work with your current PSU, this video is for you. Picking the right wattage is incredibly important, as you can easily run into overcurrent protections, or worse on cheaper power supplies, you can start to have degraded power which can damage literally every component in your system. So, why is it so hard to get the right wattage? Well, custom computers are complicated. Two systems can need completely different power supplies – one with an i9 and a 4090 would need a considerably higher wattage than an i5 and 4060. In recent years we’ve also discovered a new problem, which is that when a graphics card fully switches on to start rendering a game, it often draws an incredibly high amount of current – known as a current spike – which, if your power supply isn’t suitably oversized, can trip the overcurrent protections and just shut your system off in an instant. 

Now, seeing as BeQuiet sent over this Straight Power 12 850W fully modular power supply, Gigabyte sent over this RTX 4080 Super, and I have NVIDIA’s PCAT tool to measure the actual power consumption from the GPU, let me show you what the power usage looks like. For some context, the 4080 Super has a total graphics power rating of 320W, but under regular usage – say benchmarking in Hitman 3 on medium settings – I’m seeing more like 200W. There’s a fair bit of variation depending on what’s on screen, but considering it is meant to be running at 320W, this seems low. It turns out if you enable ray tracing and turn up the settings, it gets considerably more power hungry. Cyberpunk on Ray Tracing Overdrive pushes the power consumption up to around 280 to 300W, although in my testing nothing got to the 320W rated figure. Interestingly I was using HWInfo to record data at the same time as PCAT, and while the power reported matches very well, the actual values are slightly lower than what PCAT reports. There isn’t too much in it, but it’s worth keeping in mind that software reported values might be a touch lower than actual. 

So you only need like a 400W PSU for a 4080 Super then, right? Well, no – and for several reasons. First is that the GPU isn’t the only power hungry component in your PC – your CPU is the other big draw, and looking at the same data from HWInfo you can see that adding in the CPU can spike the power required to almost 400W. This obviously doesn’t include all the other components in your system that draw power – fans, water cooling pumps, RGB LEDs, your motherboard, storage, RAM and plenty more. In theory you likely could run this system from a 500W power supply, if not for those inrush current spikes. Now both PCAT and the software reporting aren’t fast enough to capture that, but as plenty of people found with the 20 series GPUs, when they load up your system instantly switches off as the power supply’s overcurrent protection trips, killing all power to your rig. Now NVIDIA has seemingly improved this to a degree, but realistically I’d want a 650 or 700W PSU as a minimum for this system. 

It’s also important to realise that the power consumption I’ve been talking about isn’t the same as the wall-power. I measured that too, and while PCAT was reporting around 200W of power consumption from the 4080 Super, the Straight Power 12 was drawing around 400W from the wall. That’s both thanks to the 100W or so the CPU was drawing, the other loads on the system, and the AC to DC conversion losses. That’s pretty common, and it’s worth understanding that the from-the-wall power is always going to be higher than the internally reported figures, and doesn’t matter for picking the right PSU size. The 850W this Straight Power 12 lists is DC (post-conversion) power, not 850W of input power. 

So, how do you pick a power supply wattage? Well in theory anyway you want to look up the total graphics power for the graphics card you want to use – in my case that is 320W for this 4080 super, and the maximum boost power, often called PL2 for Intel CPUs or PPT for AMD, of the CPU you want to use, so that’s 181W for this 14600K, then add a bit of extra for the rest of the components and a bit of headroom. That comes out to, oh look, 650 to 700W! You might find especially with higher end GPUs – like this actually – that you might want to upsize a touch more to cover for those current spikes, so more like this 850W unit. 

In practice, most GPU makers list a recommended PSU size, and so if you are building from scratch it’s worth following their guidance. Gigabyte recommends 850W for this card. If you’re upgrading GPU and want to make sure your current power supply is suitable, you’ll want to think about your usage, and it’s worth considering how good the power supply is. Is it 80Plus Platinum rated like this Straight Power 12, or is it just 80Plus Bronze? If it’s Bronze (or lower), you’ll likely need a higher wattage than if it’s Gold, Platinum or Titanium rated as those are better built and often more able to deal with things like those current spikes, and running closer to their maximum rating. 

As a final piece of advice, especially if you’re building your system from scratch, it’s worth getting the best quality power supply you can, and oversizing the wattage a fair bit. On the quality front, as I said at the start, your power supply is connected to every single component in your system, and a low quality power supply can literally destroy your system. As for the oversizing, when you inevitably want to upgrade later, having an oversized PSU will make that upgrade easier.