A 1000W PSU may be enough for an RTX 5090, but it's not optimal. NVIDIA recommends a power supply of at least 1000 W, but many experts recommend a power supply of between 1200 W and 1500 W to guarantee a margin of safety and optimum stability, particularly given the high power consumption of the graphics card (around 575 W) and other system components.
The model in question, with 1000 W and 80 PLUS Gold certification, meets NVIDIA's minimum recommendation, but it could be subject to full load, which is not ideal for longevity and stability. For intensive use or overclocking, a more powerful power supply would be preferable.