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EIA: US electricity generation from coal and natural gas both increased with summer heat

In August 2012, coal produced 39% of US electricity, up from a low of 32% in April 2012, when the natural gas share of generation equaled that of coal. Increased demand for electric power in the summer months—to run air conditioners—created more room in the market, and generation from both fuels increased between April and July, according to the US Energy Information Administration (EIA). The August coal share of generation is still notably lower than the 50% annual average over the 1990-2010 period.

Data for 2011 and 2012 are preliminary. Chart includes generation from the electric power sector only, excluding commercial and industrial generators. Source: EIA. Click to enlarge.

Every year during the height of summer, natural gas-fired generation from peaking generators (used to meet the highest levels of electricity demand, and typically burning natural gas) increases to meet the demand for electricity, largely regardless of fuel prices. As demand for electric power moderates in the autumn months and the need for peaking generation moderates, total natural gas-fired generation decreases. Through the fall, if natural gas prices remain higher than in the spring, coal’s share of generation may continue to increase.

The consumption of natural gas by electric power generators has been increasing each year since 2009 as lower natural gas prices allowed natural gas-fired generators to compete with coal-fired generators. Coal generation shares declined in some regions (such as the Southeast) in response to declining natural gas prices through 2010 and 2011, and then more broadly across the United States when gas prices dropped precipitously in the first half of 2012.

Natural gas demand at electric power plants was particularly high this past spring and summer. However, natural gas prices have generally increased since April, the lowest point for natural gas prices during 2012.

The electric power industry dispatches power plants based on a number of factors, including relative fuel prices, which can vary across the United States. In the West, generators have access to low-cost coal produced from large-scale mines in the Powder River Basin (PRB); in this region, the share of natural gas-fired power generation is most influenced by the availability of hydroelectric power, although increasing wind turbine generating capacity is also a factor. High levels of water runoff during 2011 led western generators to cut back on their use of natural gas.

In the eastern half of the United States, many power plants rely on bituminous coal mined in Appalachia and then transported by rail or barge to the power plant. Other plants use PRB coal transported by rail. Mining costs are much higher in this region than in the Powder River Basin (due in large part to less favorable geology and reserve depletion). The transportation charges can add significantly to the delivered fuel price to power plants. Historically, the average fuel cost of operating a combined-cycle natural gas generator exceeded that for a coal-fired generator.

Until 2010, substitution between the two fuels for electricity generation was not widespread in most US regions. However, through 2010, 2011, and most dramatically in 2012, a shift in the historical spread between the average regional operating costs of combined-cycle natural gas fired and coal-fired generators led operators to run natural gas-fired combined-cycle plants for longer periods, while generation from coal-fired generators declined substantially.

During the first half of 2012, lower consumption of coal at electric power plants led to high coal stocks and a decrease in spot prices for eastern coal. Higher-than-normal coal stocks may continue to place downward pressure on coal prices. Also, high stocks could lead to additional coal burn if the size of coal stockpiles becomes a major concern. Utilities may also resell coal, even rerouting purchases before they are delivered to the plant. Coal is also being exported in growing volumes.


Roger Pham

And it is gonna get worse, much worse, real fast. An article in Scientific American recently described how GW accelerates much faster than predicted. More solar absorption from melting of glacier and release of methane and CO2 from melting of perma-frost will accelerate GHG release much faster than human can ever do. Perhaps in a few decades, the tropics will be unlivable due to high temperatures. Sea level will rise by five feet by the end of the century. Coastal areas will be submerged, further decreasing livable landmass. It gonna be hell on earth!!!


Don't panic.
Haven't you seen the news this week? Global warming has stopped! ;)

That's right, the Daily Mail and countless bloggers have broken the story of the century!

Oh wait: "Daily Mail" & "bloggers" :-/ Never mind.

Roger Pham

Correction to my previous posting:
Sea level may rise by 5 meters (16 feet) during this century. This will submerge most coastal cities from Bangkok to NYC etc...

And thanks, ai vin, for the sarcasm.



The collective rise and fall in electricity generated from coal and gas generation seems to track the seasonal air conditioning (A/C) load of residential and commercial grid customers that totals 500 billion kWh annually, about 13% of the grid load.

This correlation between solar power and A/C load in California was studied by NREL. The document states "For example, a PV system rated at 5 MW could reliably be considered a summer peaking power source of 4 MW (=0.80 x 5)."

It notes that the correlation is higher with commercial loads, which peak between 8:00 a.m. to 5:00 p.m. and less with residential loads "because residential air-conditioning demand is greatest in the late afternoon." It further notes that the correlation "can be improved by using tracking systems and systems installed on southwest-facing residential rooftops."

My take-away is that most of the grid's air conditioning load can be provided by local sources of solar PV; more so, if thermal storage and demand management are used. Some electrical storage will be needed but mainly for other end uses, e.g., powering server farms.

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