"Unlimited energy - Lets say Fusion or something like it finally comes around and now using a couple of hundred megawatts for a an individual a month isn't out of the ordinary. How does that change things? Imagine that you can install giant chillers in the ocean and regulate its temperature regardless of surface air temperature."

This is the wrong question. Energy isn't limited any more than any other industrial product; the cheaper it is to manufacturer physical things, the cheaper it is to harness energy (and the cheaper it becomes). And conversely, in most uses of energy, you have a lot more "work" to do assembling whatever it is that uses the energy, than whatever harnesses it. It's really a problem of industry itself; and the more efficient that gets (in a fully-automated, AI-controlled industry -- many orders of magnitude), the more available it becomes. To get abundant energy you need industrial wealth (and vice versa); energy isn't an isolated problem and isn't the important one.

And on this note, there's practically no magic in fusion power. They can't drastically undercut "primitive" fission reactors, because much their infrastruture would be identical (heat exchangers, steam generators, power generation, the power grid...) Add up the costs of modern power, and fusion also carries most of them. It's like a "factor-of-two" miracle in the most optimistic fantasy -- not an order-of-magnitude, not earth-shattering magic. (Less optimistically, I don't see how anything like tokamaks or laser ICF machines can be anything but more complicated and costly than conventional power, and I haven't see any physically-sound alternatives.)

Sure, the fuel is "cheap and abundant" (if you fantasize D+D fusion becoming technically viable -- it's not so if you try the far-easier D+T using lithium-bred tritium) -- but that's exactly the wrong solution, because again, the costs are all elsewhere, on the physically-building-things part of the equation.

Heat rejection can be very serious. The current world looks like ~10^13 watts direct, anthropogenic heating (basically "energy use"), compared to a radiative forcing of ~10^15 W of anthropogenic global warming (closest figure of merit I believe) and ~10^17 W total terrestrial irradiation. (N.B. the greenhouse effect is a pretty huge "amplifier" of anthropogenic heating -- burning a ton of coal yields a certain amount of heat directly, but some 5 orders of magnitude more heat indirectly through AGW (if you integrate over the 10^3-10^4 year atmospheric residence time... don't quote me on this, I'm unsure)). Greenhouse heating is solvable, but at a couple orders of magnitude higher power consumption (say 10^15 W -- 100x present, think 10^10 people at 100 kW(th)), anthropogenic heating becomes a comparable climate issue. Approaching 10^17 W (think 10^10 @ 10 MW, if it goes there) you need geoengineering -- blocking parts of the sun (cliche), or increasing the emissivity of large swaths of the surface.

Beyond 10^17 watts you can't keep the earth anything like its natural state: even you completely block out the sun, you more than make up for it with the heat you generate on earth. The only way to dissipate heat from the earth ultimately is into space (forget ocean chillers at this point!), and the only way to do that is the way it's being done now -- radiatively. (Modulo material properties, emissivity/abosprtivity) the power you can dissipate per area goes as he 4th power of temperature (T^4) in absolute units (rel. absolute zero). So there's exactly two options: one, to drastically increase the surface area, which will look like "moving into space" -- creating a habitable world far larger in aggregate surface area than the earth (though not in mass). The other is fairly dystopian, to heat up the earth's surface beyond the habitable point -- e.g. moving into refrigerated underground cities (this is thermodynamically sound). With this insanity you could dissipate 10^22 W with a solid-carbon surface around 4000 Kelvin -- about 50,000x the current solar budget or 10 million times the current anthropogenic budget. Maybe you could still run computers at this temperature.

Anyway, 10^8 watts per capita => 10^18+ watts is no longer an "earth" solution -- you either push it off-earth, or alter the earth beyond recongition to solve heat dissipation.

(I'm actually not imaginative enough to figure out how to spend 10^8 watts. That's the order of the (average) power of launching a space shuttle once per day -- and you could probably fit a hundred people in something on that size, 1 MW per person. Even rocket-powered spaceplanes at Mach 20 aren't that costly...)