It doesn't actually matter much if our usage projections are good. What matters is 1) that the energy store is so massive that it's hard to imagine how we could possibly exhaust it, and 2) the current dominant alternative (i.e. fossil fuel) is known to be terrible for us. If we switched to geothermal and set the world up to end humanity in a thousand years, we'd still be better off than continuing our desperate use of fossil fuels and ending humanity even sooner.

The issue is we use up fossil fuels we could still continue for more years, I don't see any reason for it to end much before that. If we make mistake with earth core we would mostly surely setup end of humanity atleast. I would rather focus on getting the world to a place where willno borders and safe religion etc.. which would get lot more runtime for humans than this. If we optimize food production find a better alternative for capatalism we may live better with or with out need for fuel

Our food production is driven by fossil fuels. Everything from the farm equipment to the fertilizers we spread to the trucks we ship it in are powered by fossil fuels. When we run out of fossil fuels, we better have a back up energy source (or sources) ready, because our food production will plummet if not. So will basically every industry, since they all depend on cheap transport and automation at this time. So we'll all starve while the economy collapses around us and our infrastructure falls apart as we have neither the money nor the energy supplies to fix it.

Yeah, our dependence on fossil fuels is a huge problem, and not just because of climate change (which might also kill us).

I agree somewhat, but even though more devices are electrical or electronic and attached to the grid, they are more efficient. My 42" LED TV is using 95W, less than a 100W light bulb, whereas my old 19" tube color TV in 1978 used more.

Mobile phones didn't exist when I was young, and there are certainly a lot of them now even if they are low power devices, so it would be interesting to see electrical usage patterns pre-mobile phones vs. today.

The same goes for cars. Cars were using leaded gasoline in the US and getting 8 to 12 mpg, and now 30 to 35 mpg or greater on the highway, but do people drive more frequently, and with single riders?

Another question is would any cooling of the total Earth's heat energy be offset by global warming? The thermal differential would be less thereby slowing the migration of heat to the surface?

This assumes that nothing mayor is going to change. What if we somehow build a spaceship route from Earth to Mars and we power it through electricity. How much higher would our consumption be if we launch 10,000 spaceships every day?

Or maybe we want to terraform our own planet to counter climate change. These things could use amounts of energy orders of magnitude higher than we use today.

I'm sure 100 years ago didn't expect we would launch 100,000 airplane flights every day [0] :) Nor did they think we would send spaceships to Mars.

[0] http://www.garfors.com/2014/06/100000-flights-day.html

What if we also solve fusion and build a Dyson sphere and farm unicorns for automotive fuel?

It seems somewhat unreasonable to assume that our energy usage is going to exponentially increase due to as-yet-unforeseeable future needs and at the same time assume that we'll completely fail to find additional energy sources in the same timeframe.