
In 2010 the electricity generation in the US was dominated by a single fossil fuel: coal at 45%. By 2019 coal had declined to ~25% (the change is due to the availability of cheap natural gas with some wind, and limited solar). I expect coal will stay around this number (even with the closure of older plants) as their capacity factor will increase (produce more electricity by either being 'on' more often or generating more electricity (they often run well below maximum capacity). Natural gas is the leading source at 38%. Nuclear was the third (~20%) although the expectation is that this will decrease as units are dismantled than are constructed and as the total electricity production grows. Hydroelectric power was 7%, with the wind also contributing 7%. Note that petroleum (in the form of fuel oil and coke) did not contribute very much to electricity generation (~1%). We are still highly reliant on fossil fuels, and nuclear for electricity generation!

Total = 4.12 trillion kilowatthours
- Natural gas = 38%
- coal = 23%
- nuclear = 20%
- renewables = 17%
- wind = 7.3%
- hydro = 6.6%
- solar = 1.8%
- biomass = 1.4%
- geothermal = 0.4%
Note: Electricity generation from utility-scale facilities. Sum of percentages may not equal 100% because of independent rounding.
Changing Energy Economics Change the Renewables New Capacity Mix
As we look forward the predictions are that coal and nuclear will decrease their contribution and stabilize while natural gas and renewables will increase.

Here is another chart showing the contribution to renewables. Note the increasing role of wind and solar.

The last few lessons have had an electricity focus. However, it is important for us to keep in mind that we also have primary energy: transportation, electricity, heating (natural gas and other fuels), and fuel for industrial operations. Note that we use a great deal of petroleum (we will see in Unit 2 that this is used in transportation fuels), and natural gas! Also, note the higher contribution of biomass within renewables. It is used as industrial fuel for steam etc.
