2007 Operating Performance Rankings

by Teresa Hansen, editor in chief

The 2007 operating performance numbers look pretty similar to the 2006 numbers. The nation’s top performing power plants continue to operate efficiently, churning out the much needed megawatts that keep the country electrified. According to the figures submitted to the Energy Information Administration (EIA) on Form 906, the nation’s generating fleet of coal-fired plants, nuclear power plants and combined cycle combustion turbines generated 107,583,333 MWh more in 2007 than in 2006, for a total of 3,465,218,647 MWh.

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Perhaps the most notable event in the reporting period occurred in July 2007 with the restart of a 1,150-MW nuclear power plant—Brown’s Ferry 1—that had been shut down for 22 years. The restart of the Tennessee Valley Authority’s (TVA’s) reactor cost the company about $1.8 billion. Not only did it add much needed capacity to the generation fleet, many insiders believe it was a major achievement for the nuclear power industry, proving that the industry can complete a project on schedule and within budget (although some reports say the project exceeded the original budget by about $90 million or some 5 percent).

The tables contained in this article tell the real story of the nation’s top generators. Tom Hewson, principal at Energy Ventures Analysis, an Arlington, Va.-based firm that specializes in energy and environmental market analysis, provides the tables for Electric Light & Power’s Operating Performance Rankings each year. Hewson’s figures come directly from Form EIA 906, “Power Plant Report.” Click here to view tables.

Coal-fired performance

Typically, there is little change from year-to-year in the top 20 coal-fired plants ranked by generation (Table 1); 2007 was no exception. Southern Company’s 3,346 MW Scherer plant kept the No. 1 position. The plant managed to generate about 2,000 GWh more than in 2006, which kept them comfortably in the first place position. “My hat’s off to Scherer,” Hewson said.

Numbers two and three were the same plants as 2006; they just switched spots in 2007. Basically, to show up in the top 20 generating units in the coal-fired category, you must be big, be at or near the top of the dispatching order—which usually means you’re a low cost generator—and not have any significant generating disruptions, Hewson said. Only three plants that showed up in the top 20 generating units in 2007 were not in the top 20 in 2006. The newcomers were Xcel Energy’s Sherburne County plant, PP&L Global’s Colstrip plant and Luminant’s Monticello plant.

Monticello, a 1,880 MW plant, was the smallest on the list at No. 18. “They squeaked in,” Hewson said. The plant’s 93 percent capacity factor was enough to move it into the top 20.

As for capacity factor, there was some change in the top 20 list (Table 2) from 2006 to 2007, with 12 new plants moving into the top 20 list—four of those all the way up to the top 10. The average capacity factor of the top 20 plants increased slightly from the 2006 average capacity factor—92.4 percent in 2006 vs. 93.4 percent in 2007.

MidAmerican Holdings’ Wyodak plant was in the No. 1 spot with an impressive 98.6 percent capacity factor. “The Wyodak plant always does well,” Hewson said. “It’s going like gangbusters right now.” Because the plant sells electricity into California, there is a market for every megawatt it produces, he said.

The top 20 capacity factor list was once again dominated by Western units, with only six eastern plants making the list. Although some of the Western plants must operate with water restrictions in the summer, they still do well, according to Hewson. Most of the Western plants on the list are fueled by Powder River Basin (PRB) coals. And they are competing against natural gas-fired plants; so they are the lowest cost generators. This means that, when they are running, they are high on the dispatch list.

The top 20 heat rate list (Table 3) is very different than the capacity factor list. According to Hewson, there are four major factors that increase a plant’s efficiency (heat rate): supercritical design, adequate cooling water, low parasitic load and eastern coal.

The 2007 top 20 heat rate list certainly reflects Hewson’s statement. The list is dominated by Eastern plants. In fact, every plant on the list is located in the eastern half of the United States, and all but No. 17, Detroit Edison’s Monroe plant, burn eastern coals. (Monroe burns blended coal that contains some PRB coal.) Dominion had the most plants on the list with eight of the top 20.

Most of the top performers in 2007 were supercritical units, with Nos. 18 and 19 being the only two plants on the list that were not. No. 18, SCANA’s McMeekin plant, is a subcritical plant that obtains an “incredible” heat rate, Hewson said. “I’ve often asked the question: Why? If they were higher on the list, I’d give them a call more often.”

Natural gas combined cycle performance

Given natural gas typically has significantly higher delivered prices than either coal or uranium, combined cycle plants are often dispatched after nuclear and coal units in the regional dispatch order. However, combined cycle units can enjoy much improved heat rate efficiencies to offset a portion of their fuel price disadvantage because they can produce electricity from both direct combustion in a gas turbine and conversion of the heat in its turbine exhaust gases into steam that drives the steam turbine, Hewson said.

In several regions (New England, California and Florida), the combination of existing generation mix and regional electicity demand can place some natural gas combined cycle capacity units as baseload resources. In these regions, gas-fired combined cycle plants run more and, therefore, make it into the top 20 generation list (Table 4). Similar to the coal-fired generation list, many of the top 20 combined cycle gas fired plants that appeared on the list in 2006 were back in 2007—17 of the top 20 were the same, with the top three being identical to 2006.

Although most of the top 20 generating units were the same, the average capacity factor for the top 20 was much higher in 2007 than in 2006—59 percent in 2007 vs. slightly less than 48 percent in 2006. Hewson said this reflects the current trend of fewer baseload plants being constructed and more existing cycling capacity being used to meet demand.

“Florida depends heavily upon natural gas for power generation. It accounts for more than 44 percent of the total instate generation; so many of the top 20 generators are located there,” Hewson said. California, Arizona and Texas, which have added a lot of new gas-fired generation to meet growing load demand in the past decade, also had several plants on the list. In areas where a lot of gas is used to generate electricity, gas plants are dispatched earlier than other plants because they are not competing with cheaper fuels such as coal. Therefore, they are running more, he said. Many of the newer gas-fired combined cycle plants are also displacing older gas-fired steam plants, which move them higher up on the dispatching list.

Unlike the top 20 generating plants, the list of top 20 combined cycle plants by heat rate (Table 5) contains only five of the same plants that made the list in 2006. “Heat rate is what people focus on when they are determining cost,” Hewson said. “With a high heat rate, you can afford to use more expensive fuel. All top 20 plants are highly efficient.”

The top 20 combined-cycle plants based on capacity factor (Table 6) is similar to the heat rate list in that it only contains seven returning plants. Another similarity to the other two combined cycle lists, the average capacity factor for the top 20 was much higher in 2007 than in 2006—86.6 percent vs. 70.7 percent, respectively. Again, Hewson contributes the increase to more operating time and greater demand for the plants.

Although the capacity factor of the 2007 top 20 plants was significantly higher in 2007 than 2006, the MWh generated was lower. Hewson attributes this to the fact that several of the plants on the list are cogenerators, producing steam as well as electricity. Steam was the main product of many of these cogeneration plants, which resulted in fewer megawatts being produced.

Nuclear performance

The nuclear story doesn’t change much from year-to-year. The 104 operating units may get shuffled in the top 20 lists, but as a whole the industry achieves remarkable performance numbers. The average capacity factor for the nation’s 104 operating units was 90.28 percent in 2007, about 18 percentage points above the reporting coal plants’ average capacity factor.

Like in most years past, Pennacle West’s three-unit Palo Verde plant generated more megawatts than any other nuclear power plant (Table 7). “They are big. It’s hard to beat them (Palo Verde),” Hewson said.

Palo Verde will have a harder time keeping the top spot now that TVA’s Browns Ferry 1 is on line. Brown’s Ferry jumped from No.15 in 2006 to No. 3 in 2007, and the new unit operated for only half the year. “There’s nothing like getting another unit to move you up on the list,” Hewson said.

As with the coal-fired plants, to make the top nuclear power plant generating list, a plant must be large. While many of the rankings in the top 20 listing changed, 19 of the 2007 top generating plants were also on the 2006 list. The position on the list is determined by the timing of scheduled outages and refuelings. The only newcomer in 2007 was San Onofre, which moved into the 19th spot. Entergy’s Arkansas Nuclear One fell out of the top 20.

The story on nuclear capacity factor remains pretty much the same. The average capacity factor of the top 20 plants (Table 8) was 96.65 percent, down slightly from 2006’s average capacity factor of 97.15 percent. South Texas project had the highest capacity factor this year with a remarkable 99.83 percent, which was up slightly from the 2006 high of 99.7 percent. “With most plants operating on an 18 month refueling cycle, the nuclear fleet is able to achieve very high capacity factors,” Hewson said.

Only four of the top 20 plants by capacity factor returned from 2006 to 2007. The shakeup in the list is again explained by the timing of scheduled outages and refuelings. “Those plants that didn’t have a scheduled outage in 2007 moved up and those that did, moved down,” Hewson said.

In addition to the tables included in this article, Hewson provided additional tables that deal with the generators’ NOX and SO2 emissions that were not included due to space limitations. Those tables are included in the online version of this article.


  • The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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