What is it about TS4 that makes a computer run so hot?

It's CPU intensive and poorly optimized. The team is apparently working on the simulation lag issues; hopefully that will include optimizing the code a bit so it's no longer as taxing on the CPU.

You're right about being CPU intensive. On my last comp it would sometimes run it at over 90%

I have to use a cooling pad for my laptop when playing. Just ordered a new one with six fans. I was seriously considering a new laptop but after seeing you're having issues I doubt that would be the solution.

I just exited the game, and 30 seconds after that, the fans spun down to normal

I think it's orgin related. Origin without playing the sims, takes my cpu up to 90 plus. Massively slows down everything until I force quit origin and restart the PC.

Yeah, for some reason it feels like the game runs better in offline mode. Origin might be one reason.

My RTX 3080 seems to handle the game pretty well and the computer doesn't get very warm, not compared to some other games, I still get massive framedrops from time to time though and the game is very cpu intensive. I don't know how people manage to play this on old computers. At least not on older saves.

Yup can confirm that Origin is causing issues. If I forget to close Origin after playing sims my pc bluescreens when playing other games. Only happens when Origin is also running.

Yesterday I played Sims 4 longer than I usually do. I have a gaming laptop that heats up really badly after about an hour of playing and I use a cooling pad. After playing about 3 hours yesterday I noticed that my laptop smelled like something was burning. I immediately stopped playing and closed the laptop.
Today I've used my laptop already and it seems fine. I hope it's not going to break up when I will play Sims later today. I'm definitely not going to play more than 1-1,5 hours this time.

Thanks for the tips about Origin, everyone--when I play next, I'll try offline mode

The Sims is very much a CPU hog.... I remember the Sims 3 and 2 also ran my computer(s) much hotter back then too, and I've always had the latest-greatest gaming computers with massive cooling systems etc throughout all the years (I take my gaming very seriously LOL). Sims 4 doesn't seem to be any better, even though this one is supposed to be minimized for lower-end computers... but it still sucks a ton of CPU usage just like the previous generations.