I got one shortly before they became hard to get over a year ago. And it says that it draws around 350 watts when it’s at full throttle. That’s not a space heater, but it’s certainly a bit of heat to get rid of. It becomes very noticeably warmer in my room when I’m running it.
3080s benefit from a mild undervolting. They run hot out of the box and actually perform better with the voltage dialed back a little since it then maintains more consistent temp than doing a whole “run fast & hot, thermal throttle, cool down, run fast & hot again, thermal throttle…” loop. I think Nvidia overtuned them from the start. To be clear, you can run and game on them just fine as is, they just perform better with a little tinkering. I got an extra thousand points on my Time Spy score after undervolting my card.
Hard to recommend a card without a budget but I will again say not to sleep on the AMD Radeon cards. You can get an RX 6900 XT, the competitor to the RTX 3090, for $700 on Newegg or a more modest 6600 XT for a mere $320.
As for the GTX 770, it’s probably on its way out. You can try taking it all apart and cleaning it and applying fresh thermal paste but it sounds like you might have circuitry issues.
I was coming in to ask about that. Seems to be the consensus in other places.
I don’t have a strict budget, but want to be reasonably confident of the value for the cost. I’ll probably go for a 3080, but wait a while to see how prices evolve. I can limp along in Minecraft with minimal graphics.