Electricity – Then, Now and Tomorrow

Author: Velocity Suite ISO Data Analyst

A recent article published by the Wall Street Journal caught the eye of the Velocity Suite blog team and it got us thinking: what’s the data behind these electricity generation statistics and how will these numbers change in the future. The article is here:

Coal Still Is Top Source of Electricity in U.S.; Where Does Your State Stand?

To quickly summarize: Coal is still the primary fuel used for electricity in the US, but this is starting to change. We took similar EIA data and mapped it by year covering the timeframe of 2001 through 2014 (May 2014 was the last data available at the time of writing). A time series map of the data is available below.

TSA Generation by Year BIG
Generation Time Series Map

The data is summarized in tabular form below and it indicates that 2014 isn’t the first year we’ve seen coal on the decline and gas in an upswing. In fact, 2014 hasn’t seen the same coal to gas displacement that we saw in 2012 or 2013. For example in 2001, coal was the leading type of fuel burned in 32 states. By 2012 this had declined to 23 states. At the same time, gas has more than doubled – seven states burned more gas than any other fuel in 2001. But in 2012 this had increased to 15 states. 2014 has seen slightly higher numbers for coal and slightly lower numbers for gas, but this may very well change as we get into the hottest months of the year.

Count of Charts by Fuel Data Grid final2
Figure 1: Comparing the number of states where coal, gas or another fuel leads in generation MWhs

There are a number of items that have caused the displacement. Coal power plants are aging and retiring. At the same time, larger and more efficient gas and renewable energy units are being introduced to the grid. We’ve discussed why gas and renewable power plants are being built over coal plants in previous blogs, but the reasons include lower gas prices, increased supply of natural gas, local and federal incentives for renewable energy development and the expectation of EPA regulations around CO2.

In researching this angle of the story we identified an interesting statistic. Although coal is still the leading generator of electricity there are actually more MWs of gas capacity in the US. Capacity is what a unit is capable of, whereas generation is what a unit actually produces. Just because a plant exists doesn’t mean it is going to generate energy and create electricity.

Total Capacity by Fuel final2
Figure 2: MWs of Capacity by Fuel

This creates an interesting question- why don’t we see more gas generation and electricity if there are so many gas power plants in the United States? You’d expect that more capacity would mean more generation. But, that’s not necessarily the case. Different types of units run at different times and with different frequencies. Nuclear plants and coal plants tend to run consistently. They are what we call base load units (in that they are available for the base load or demand in an energy system). Gas and oil units are peaking in that they respond to fluctuations in demand (the peak value) during the day. An example is below.

ERCOT Unit Generation for One Week 2014 final2
Figure 3: Analyzing Generation by Hour for One Week in 2014 in Texas

If we look at this week of data in ERCOT (Electric Reliability Council of Texas) you can see that nuclear and coal generation are relatively constant through the week. As the need for energy changes throughout the day – we turn on our lights, boot up our computers and crank up the AC – natural gas units generally respond.

We can learn about tomorrow by looking at a little more history. 2012 presented an interesting scenario as gas prices dropped to record lows. This was the year when gas generation was the highest. During this time frame we started to see what could very well be the future- gas units acting like base load and coal units acting like peaking units.

ERCOT Unit Generation for One Week 2012 final2
Figure 4: Unit Generation by Fuel and Hour for a Week in Texas in 2012 during Low Gas Prices

What else can we gather about the future? Our team is currently tracking over 30,000MWs of possible coal retirements in the US. At the same time, almost 100,000 MWs of new gas capacity and over 105,000 MWs of new wind capacity is in the pipeline. We can further assume that less coal capacity in this case will translate to less coal generation. And we expect to see additional generation from the gas and renewable units in return. Check out this data and more in Velocity Suite – where you can track generation data down to the hour and future capacity information across all of North America. Then you can build your own analysis around historical and future electricity trends.


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