My microwave is 1200W
If I could redirect all that heat to at least cook food, that would be great
(your point is valid, though)
Computers, in general, are space heaters that incidentally allow rapid computation. Remember the comments, when the Pentium came out, about its heat dissipation being similar to a toaster? My, we've come a long way...
BTW, a 15A 120VAC circuit is designed for 12A continuous (80% of peak). In round numbers, that's 1.4 kw. That's the safe limit for something that is the only load on a entire standard US plug circuit. Usually, there are a few other loads, like desk lamps, clocks, etc., so you have less than 1.4kw available to burn. 8A (just under 1kw) is usually considered safe for a typical 120VAC US circuit. Unless you want to install a dedicated circuit or 2 for your computer, as some audiophiles do for their music rooms. Do a dedicated 20A circuit and you can get a bit more: 16A, good for 1.9kw.
According to my UPS' monitoring software, my desktop currently uses between 60-130W for both the computer and the monitor. So I don't really have a dog in this hunt.
Edit: amusing anecdote - back in the Radio Shack Model 1 days, the major heat dissipation issue was the RAM chips, not the Z80 CPU. And, of course, the brute-force voltage regulator. The service manual for the computer (it had a complete manual, with schematics, board layout, parts list, and ROM API, available at retail) noted that one should not use a common method for checking whether a RAM chip was working - touching it - unless one wanted the manufacturer's logo burned into one's fingertip...