AMD Radeon RX 7900 XTX or GeForce RTX 4090 both need at least 850W power supply
Both GPU vendors have now announced and partially released their high-end graphics cards based on the latest architecture.
ASUS updated its power supply recommendation chart for NVIDIA Ada Lovelace and AMD RDNA3 GPUs series, all four cards so far. Since none of this information is secret anymore and ASUS is actively selling or developing custom designs based on each architecture, the recommendations are very accurate.
NVIDIA has officially recommended at least 850W power supply for its RTX 4090 GPU, the flagship of the current series. The recommendation from AMD is lower, the company thinks that 800W PSU should be sufficient. However, the PSU recommendations should always account for other components, in this case, the CPU is the most power-hungry component.
For mainstream setups with Intel Core i5 or Ryzen 5, the 850W PSU should be suitable for RTX 4090/7900XTX GPUs, while 750W should be powerful enough for RTX 4080 and RX 7900 XT cards. However, those recommendations are higher for Intel Core i7/Ryzen7 and Core i9/Ryzen 9 systems. For such systems ASUS recommends at least 1000W of power for RTX 4090 and 850W to 1000W PSU for Radeon XTX.
The company is also sharing recommendations for Intel HEDT and AMD Threadripper series. Here both cards should be paired with at least 1200W PSU. Meanwhile, The RTX 4080 and RX 7900 XT cards should both work with 750W and 850W power supplies, the latter being an option recommended even for high-end systems.
Although this is not covered by the document, the RTX 40 series are equipped with the new 16-pin PCIe Gen5 power connector. That said, it would make sense to look at ATX 3.0 power supplies with native implementations of 12VHPWR cables, which ASUS is offering with their ROG Loki series.
Neither AMD nor NVIDIA have confirmed the rest of their new lineups, therefore no further recommendations were made.