Electricity is generated using the following fuel sources: coal, nuclear, natural gas, petroleum and renewable resources.  Renewable resources include hydropower (which traditionally makes up over 95 percent of renewable generation), geothermal, biomass, wind, solar, and photovoltaics.  Another source, categorized as “other”, includes: hydrogen, sulfur, batteries, chemicals, and purchased steam. 

Shares of Net Electricity by Energy Source, 1992 and 1998

This chart shows the relative decline since 1992 of coal, nuclear and other renewables, and the increasing share of natural gas, hydropower and petroleum.  Coal and nuclear is forecasted to continue to decline, and natural gas is projected to increase to offset this decline.

Here is a pie-chart chart showing the amount of electricity generated in 1999 by fuel type.  The categories are a little different, but you can still see that coal, nuclear, natural gas and hydroelectric dominate.

The next chart is interesting, because it shows the generating capacity for 1999.  What’s noteworthy is that natural gas and oil/petroleum have a much higher proportion of the available capacity (22% and 9%, respectively), and yet (from the chart above) they make up a smaller proportion of the actual power generated (15% and 4%, respectively).  In other words, more power plants fueled by natural gas and oil sit idle than those fueled by coal and nuclear materials.  This is because the fuel cost of coal and nuclear is lower, but the cost of building the power plant is higher.  So once a nuclear or coal power plant is built, it makes economic sense to keep it running as much as possible. Also, it takes much longer to start and stop nuclear plants than natural gas turbines (days and weeks, versus minutes). So natural gas and oil power plants are more commonly used for ‘peaking’, and nuclear and coal are used to generate the ‘baseload’.

Let’s take a close look at Coal.