In terms of energy, rendering (or other computing workload) is a side effect of the work done, not the work itself. Work in the physics sense
is energy changing from one form to another. All the electrical energy that goes into a computer has to come out in another form to "do" anything; that is, perform work. That ends up being kinetic energy in the fans and the air they're moving (we can consider the sound generated by fans and HDDs as kinetic, but there's hardly enough of that to matter), a small amount of EM radiation from the various electrical components, a few milliwatts as signaling to your monitor or whatever, and maybe another mW or three as light from LEDs. The rest becomes heat. Those are the only options. Unless you've got some weird custom setup with a rechargeable battery, none of the energy becomes chemical, and if you're turning a bunch of energy into light, something has gone VERY wrong.
Long story short: >95% (est) of the electricity drawn by a PC becomes heat.