4K Render is too slow on RTX 4090?

Hello,

I just got a new PC 2 days ago with an RTX 4090, intel i9-14900KF, and 128gb ram.
I tried to render an 800-frame sequence to test it out. When I tried to render at 4k resolution, it rendered 12 frames in 40 minutes and said the rest would take like 14 hours. When I rendered at 1080p, the whole 800-frame sequence took just 10 minutes.

Does anyone know why there is this discrepancy? All the other settings (using Movie Render Queue) except resolution are the same between the two render attempts. This is my first ever PC (I’ve been using Unreal on Mac until now) so I know close to nothing about graphics cards, etc. but I know the 4090 is meant to be faster at rendering 800 frames of 4k than 15 hours.

Any advice on this would be immensely appreciated. I do close all the programs on my computer while rendering and I checked to make sure (in the GeForce Experience program) that the GPU was actually being used (it was, at 99% utilization). My computer’s power supply is the Thermaltake Toughpower GF3 1000W in case that is important.

Thank you!!!