It takes 1.07 pounds of coal to generate 1 kWh.
http://www.eia.gov/tools/faqs/faq.cfm?id=667&t=2
So for 150 homes using 11,280 kWh per year, we need (150 * 11280) / 2000 = 846 tons of coal.
An average railcar holds 120 tons of coal.
http://www.matts-place.com/trains/coal/coaltrain_basics.htm
So in place of one box of borax, we need about 7 railcars of coal.
