One Hundred Thousand Trains of Coal – updated

The latest SEIA report for Q2 2014 shows faster than Moore’s Law growth in PV installations. Installation in 2014 will be 8X the installations just four years ago and doubling again by 2016. Local and state incentives combined with a continued drop in panels and installation infrastructure led the recent growth. Future growth will benefit from State mandates on utilities to increase renewable energy generation.


The SEIA Year-End results for 2010, released earlier this month show a 878MW of solar photovoltaic installations in the US. Each MW of installed capacity will generate about 1.6GWHr of electricity per year which is the equivalent of burning 1600 tons of coal in a generator. Coal is shipped around the country on railroad trains. A typical train will carry ~11,000 tons of coal. So the installed PV capacity in 2010 will save (878 x 1600/11,000) or 127 trains of coal this year and every year for the next thirty or so years. Solar PV is forecast to growth at a 50% rate for the next several years, reaching ~10GW by 2020. At that time the cumulative base will be saving ~3800 trains of coal per year.

If those numbers sound impressive, consider that the US consumes ~90,000 railroad trains of coal each year for electricity. How much solar or renewable capacity is needed to replace ALL of that coal. Let’s start with round numbers.

  • US consumption of coal ~1B tons ~600GW of solar PV
  • The average home PV system is 4.7KW. 600GW would require 127M residential PV systems – more than the current base of US homes!
  • At 15W/sq-ft, 600GW would require 40B sq-ft or ~10X the total commercial rooftop area in the US.
  • Solar currently costs ~$4/W installed. The DOE’s SunShot program is targeting $0.75/Watt by 2020. The cost of 600GW in 2020 would be $450B.
  • There are cells technologies with efficiencies above 30%. There are concentrator systems that increase power density more than 10X.
  • At 150W/sq-ft and $0.50/W, we could replace 100,000 trains of coal with 4B sq-ft of solar panels at a cost of $300B. Or about what we spend on foreign oil each year.