The comic that started it
For me it started with a comic. Randall Munroe's xkcd 1162, "Log Scale" charts the energy density of different fuels. The bars for wood, coal and gasoline fit on the page. The bar for uranium doesn't. To show it, the comic has to unfold a long paper stack.
I laughed, then I kept thinking about it. If one fuel is that much denser than the others, why wasn't it the center of every conversation about energy? This site is my attempt to work through that question in public, one careful step at a time.
The goal: 100 MWh per person per year
Everything here points at one number: 100 megawatt-hours of energy per person per year. That's a level where heat, light, clean water, travel and industry stop being scarce. The home page explains why we chose it.
Getting there takes a lot of energy, and that energy has to come from somewhere. So the useful questions are: how much fuel, how much land, and how reliable is the result?
Density is destiny
The Nuclear Energy Institute puts it plainly: one uranium fuel pellet, about the size of a fingertip, creates as much energy as one ton of coal, 149 gallons of oil, or 17,000 cubic feet of natural gas.
That density follows through the whole chain. A reactor doesn't need a train of fuel every day. NEI notes that a plant typically stops every 18 to 24 months to replace about a third of its fuel. The waste is small for the same reason. The U.S. Department of Energy says all the used fuel the U.S. industry has produced in 60 years would fit on a football field at a depth of less than 10 yards.
Small inputs, small outputs, and a lot of energy in between.
Land: an honest comparison
Every energy source uses land. The fair way to compare them is land per unit of electricity actually produced, counted over the whole life cycle: mining, building, operating and waste. Our World in Data did exactly that using UNECE life-cycle data:
- Nuclear is the most land-efficient source. Per unit of electricity it needs about 50 times less land than coal, and 18 to 27 times less than ground-mounted solar.
- Coal uses a lot of land once you count the mines.
- Solar depends heavily on how it's built. Rooftop solar adds very little new land, because the roof is already there.
- Wind varies the most. Our World in Data measured large wind farms at anywhere from about 8 to 184 m² per MWh. Much of that land is still farmed between the turbines.
The DOE gives a plant-level version of the same picture. A typical 1,000-megawatt U.S. nuclear facility needs a little more than 1 square mile. Citing NEI, it says wind would need about 360 times more land for the same electricity, and solar PV about 75 times more.
None of that makes solar or wind bad. It just means they're spread out, and spread out can be a good thing. I'm a fan of agrivoltaics, where panels and crops share the same field. Research summarized by Our World in Data finds that under some conditions crop yields under the panels can even go up, thanks to shade and better water balance. Wind leases and solar on farmland put income straight into rural communities. That's generation that grows into places instead of being imposed on them.
Reliability: boring in the best way
Land is one thing. Showing up every hour is another.
The DOE reports that U.S. nuclear plants run at maximum power more than 92% of the time, the highest capacity factor of any source. Nuclear has supplied roughly a fifth of U.S. electricity every year since 1990.
That's what I mean by boring. Fission is methodical. It runs, it refuels on a schedule, and it runs again, whatever the weather.
Coal, gas, and the bridge
I'll be direct about coal. By Our World in Data's estimates, coal causes about 24.6 deaths per terawatt-hour from accidents and air pollution. Nuclear comes in at about 0.03, and that figure includes Chernobyl and Fukushima. Coal is the source we should be retiring first.
Natural gas is a different story. At about 2.8 deaths per terawatt-hour on the same measure, it's far cleaner than coal. It's flexible, it can ramp up when the sun sets or the wind drops, and it has already pushed a lot of coal off the grid. I see gas as a bridge and a firming partner, not a villain.
Where this leaves us
No single source does everything. Solar and wind are cheap to add and grow well alongside farms and towns. Gas fills gaps. Fission adds what the rest can't easily provide: a huge amount of steady energy from a tiny amount of fuel on a small patch of land.
If the goal is 100 MWh per person, density matters. That's why I keep coming back to that unfolded paper stack in the comic.
Safe, methodical, reliable. That's the case for fission.