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Your laptop GPU often has a "TDP" or Thermal Design Power number buried in its specifications, measured in watts. It's easy to gloss over, but TDP could be a key performance number that you overlook at your own peril.
What Is TDP?
The Thermal Design Power (or sometimes Profile) is essentially the heat budget of a processor. It's designed to generate up to that amount and no more. TDP isn't quite the same as the amount of power that a processor like a GPU uses, but it's in that ballpark.
What TDP is really about is cooling, If a GPU has a TDP of 100W, then it needs a cooling solution that can handle 100W of heat energy and move it out of the system quickly enough to prevent GPU throttling or even an emergency shutdown.
What Does TDP Mean in a Laptop?
Laptops have to be power efficient, they have all their components squashed into an incredibly tight space, and they don't have much room for cooling systems. This means the cooling system that fits in a given laptop chassis puts a limit on the TDP that its CPU or GPU can reach.
The higher the TDP for a component, the faster it can run, the longer it can run under heavy loads, and the more power it can use to do it. In other words, if you have two 100% identical GPUs, but one has a TDP of 65W and the other 130W, there can be a massive difference between them when it comes to performance.
The Problem With Modern Laptop GPU Ratings
Knowing a laptop's GPU TDP matters now more than ever. Why? It all has to do with how GPU makers, NVIDIA in particular, are naming their mobile GPUs. In the past, you would get different names for the low-TDP and high-TDP variants of a GPU. For example, the GTX 1080 Max-Q performs about 10-15% slower than the normal model.
With the latest generation of NVIDIA GPUs, the difference in names is gone. Instead, each GPU can be set by the laptop manufacturer for a specific TDP. The RTX 3060 mobile GPU ranges from 80W to 115W with eight TDP levels in total. The 80W card has a GPU clock range of 900-1425 MHz, and the 115W variant ranges from 1387-1702 MHz. That's a big difference in clock speed, without any indication in the name pointing to that difference.
The good news is that NVIDIA now requires TDP figures to be published in gaming laptop specification sheets. However, if you don't know what the number means or that you should pay attention to it, you're not really any better off.
Look to the Benchmarks
The best way to approach buying a laptop with a modern GPU in it is to look at the laptop specification sheet and see what TDP that GPU is rated for as well as the clock speed range. Following this, you should compare it to the range of possible TDPs for that GPU and see where in the stack your prospective GPU falls.
However, the most important thing is to look for benchmarks between the different TDP levels for a given GPU. If at all possible, you should find benchmarks for the specific laptop model you're looking to buy. Buying a high-performance laptop is a big investment and you don't want to find out that your low-TDP variant falls short of what could have been a great performance.
Of course, if you prefer a cooler-running laptop with longer battery life, you might actually want the low-TDP variant of that movie processor. What's important is getting the hardware that you actually wanted.