In a nutshell: Nvidia has already clarified its power supply recommendations for new RTX 40-series graphics cards, but some add-in board (AIB) partners have issued their own guidance that is much higher than Nvidia's.
Tom's Hardware recently inspected the recommended wattage requirements for various AIB partners and found a range of suggestions. Several cards including the Galax RTX 4090 SG / ST, the Inno3D RTX 4090 X3 OC iChill Black and the PNY RTX 4090 Verto Epic-X call for an 850W power supply which mirrors Nvidia's guidance.
Three others – the Asus RTX 4090 ROG Strix OC, the Gigabyte Aorus RTX 4090 Master and the Zotac RTX 4090 AMP Extreme / Trinity – should be paired with a 1,000 watt power supply at minimum. Palit, meanwhile, recommends at least a 1,200 watt PSU for use with its RTX 4090 GameRock OC. Curiously enough, the specs list graphics card power at 450W, the same as most every other RTX 4090.
A handful of manufacturers including Gainward and Colorful did not share PSU recommendations for their RTX 4090 offerings. If you are eyeballing one of those cards, it would probably be best to follow Nvidia's guidance.
While we won't know for certain until we perform some hands-on testing, it is probably safe to say that 1,200 watts is overkill. One could argue that Nvidia's 850W recommendation doesn't account for all variables. For example, heavily overclocked flagship CPUs consume a lot more power than mainstream chips, and what if your system is also filled with gobs of storage and other dedicated hardware?
What's more, not all PSUs are created equal. It is certainly plausible that a budget 850W PSU could struggle under a heavy load. Perhaps Palit and others are recommending higher-powered units in hopes of eliminating weak points before they even have a chance to surface.
Nvidia's RTX 4090 launches on October 12 starting at $1,599. The RTX 4080 12GB and 16GB variants, meanwhile, are slated to arrive sometime in November from $899 and $1,199, respectively.
Keep an eye out for our RTX 4090 review coming next week.