Did ERCOT’s shift from zonal to nodal market design reduce electric power prices?

Jay Zarnikau, C.K. Woo, and Ross Baldick have examined whether the shift from a zonal to nodal market design in the ERCOT power market had a noticeable effect on electric energy prices. The resulting article, published in the Journal of Regulatory Economics, and this post may be a bit geekier than we usually get around here. I’ll try to tone it down and explain the ERCOT change and the effect on prices as clearly as I can.

The topic is important because the shift from zonal to nodal market structure was controversial, complicated, expensive, and took longer than expected. Problems had emerged shortly after launch of the initial zonal-based market and the nodal approach was offered as a solution. Some market participants had their doubts, but rather quickly ERCOT began the move to a nodal design. Note that phrasing: “rather quickly ERCOT began the move.” It took several years for ERCOT to actually complete the process.

In part the shift was promoted as a more efficient way to run the market. Zarnikau, Woo, and Baldick looked at the effect on prices as one way to assess whether or not the resulting market has worked more efficiently. They conclude energy prices are about 2 percent lower because of the nodal market design.

Don’t get hung up on the 2 percent number itself, but think of the shift as having a modest downward pressure on prices.

The result is consistent with an understanding one would gain from the study of power systems engineering as well as with what power system simulations showed. The point of the Zarnikau et al. study was to investigate whether data analysis after the fact supported expectations offered by theory and simulation. Because there is no better empirical study (so far as I am aware) and because their results are consistent with well-founded expectations, I have no reason to doubt their result. I will contest one interpretation they offer concerning the current resource adequacy debate in Texas.

Some background (which beginners should read and others can skip).

The delivery of electric energy to consumers is a joint effort between the generators that create the power and the wires that bring it to the consumer. The wires part of the system are not simple links between generators and consumers, but rather complicated network of wires in which consumers and generators are connected in multiple ways. The added flexibility that comes with networking helps the system work more reliably and at lower cost.

The network also comes with a big coordination problem, too. Power flows on the network are not individually controllable. With many generators producing power for many consumers, parts of the power grid may become overloaded. One key job of the power system operator is to watch the power flows on the electric grid and intervene as needed to prevent a transmission line from being overloaded. The intervention generally takes the form of directing a generator (or generators) contributing to the potential overload to reduce output and directing other generators to increase output. In areas outside of regional system operators, this function is done on a piecemeal basis as problems arise. A significant benefit coming from full-scale regional power markets integrated with system operations (such as ERCOT in Texas after the switch to a nodal market and in other similar ISO/RTO markets) is that such coordination can be done in advance, with more information, mostly automatically, and more efficiently than piecemeal adjustments.

Described in simpler terms, the regional power system operator helps generators and consumers coordinate use of the power grid in the effort to efficiently satisfy consumer demands for electric energy. A zonal market design, like ERCOT started with, did minimal advance coordination. The nodal market design and related changes implemented by ERCOT allowed the market to do more sophisticated and efficient coordination of grid use.

About data challenges.

In order to assess the effects on prices, the authors couldn’t simply average prices before and after the December 1, 2010 change in the market. The power system is a dynamic thing, and many other factors known to affect electric power prices changed between the two periods. Most significantly, natural gas prices were much lower on average after the market change than during the years before. Other changes include growing consumer load, higher offer caps, and increasing amounts of wind energy capacity. In addition, the prices are generated by the system has been changed, making simple before and after comparisons insufficient. For example, rather than four zonal prices produced every 15 minutes, the nodal market yields thousands of prices every 5 minutes.

One potentially significant data-related decision was a choice to omit “outliers,” prices that were substantially higher or lower than usual. The authors explain that extreme price spikes were much more frequent in 2011, after the change, but largely due to the summer of 2011 being among the hottest on record. At the same time the offer caps had been increased, so that prices spiked higher than they could have before, but not because of the zonal-to-nodal market shift. Omitting outliers reduces the impact of these otherwise confounding changes and should produce a better sense of the effect of the market change during more normal conditions.

Their conclusion and a mistaken interpretation.

Zarnikau, Woo, and Baldick conducted their price analysis on four ERCOT sub-regions separately so as to see if the change had differing impacts resulting from the changeover. The West zone stood out in the analysis, largely because that zone has seen the most significant other changes in the power system. The two main changes: continued sizable wind energy capacity additions in the zone, and more substantially, dramatic electrical load growth in the region due to the recent oil and gas drilling boom in west Texas. Because the West results were a bit flaky, they based their conclusions on results from the other three zones. Across a number of minor variations in specifications, the authors found a price suppression effect ranging from 1.3 and 3.3 percent, the load-weighted average of which is right around 2 percent.

So far, so good.

But next they offered what is surely a misinterpretation of their results. They wrote:

[T]he reduction in wholesale prices from the implementation of the nodal market might be viewed by some as a concern. In recent years, low natural gas prices and increased wind farm generation have also reduced electricity prices in ERCOT which has, in turn, impaired the economics of power plant construction. … It appears as though the nodal market’s design may have contributed to the drop in prices that the PUCT has now sought to reverse.

Strictly speaking, the goal of the Public Utility Commission of Texas hasn’t been to reverse the drop in prices, but to ensure sufficient investment in supply resources to reliably meet projected future demand. Lower prices appear to be offer smaller investment incentives than higher prices, but there is a subtle factor in play.

The real incentive to investment isn’t higher prices, it is higher profits. Remember, one of the most important reasons to make the switch from a zonal to a nodal market is that the nodal market is supposed to operate more efficiently. Zarnikau, Woo, and Baldick notice that marginal heat rates declined after the shift, evidence consistent with more efficient operations. The efficiency gain suggests generators are operating at an overall lower cost, which means even with lower prices generator profits could be higher now than they would have been. It all depends on whether the drop in cost was larger or smaller than the drop in prices.

The cost and profit changes will be somewhat different for generators depending on where they are located, what fuel they use, and how they typically operated. I’ll hazard the guess that relatively efficient natural gas plants have seen their profits increased a bit whereas less efficient gas plants, nuclear plants, and coal plants have likely seen profits fall a little.

FULL CITE: Zarnikau, J., C. K. Woo, and R. Baldick. “Did the introduction of a nodal market structure impact wholesale electricity prices in the Texas (ERCOT) market?.”Journal of Regulatory Economics 45.2 (2014): 194-208.

Here is a link to a non-gated preliminary version if you don’t have direct access to the Journal of Regulatory Economics.

AN ASIDE: One modest irony out of Texas–the multi-billion dollar CREZ transmission line expansion, mostly intended to support delivery of wind energy from West Texas into the rest of the state, has turned out to be used more to support the import of power from elsewhere in the state to meet the demands of a rapidly growing Permian Basin-based oil and gas industry.

The case for allowing negative electricity prices – Benedettini and Stagnaro

Simona Benedettini and Carlo Stagnaro make the case for allowing negative prices in electric power markets in Europe. A few of the larger power markets in Europe allow prices to go negative, but others retain a zero price lower limit. Benedettini and Stagnaro explain both why it is reasonable, economically speaking, to allow electricity prices to go negative and the hazards of retaining a zero-price minimum in a market which is interconnected to markets allowing the more efficient negative prices.

It is all good, but I can’t resist quoting this part:

Negative prices are not just the result of some abstruse algorithm underlying the power exchange and the functioning of the power system. They are also, and more fundamentally, the way in which the market conveys the decentralized information that is distributed among all market participants, and that cannot be centralized in one single brain, as Nobel-prize winner Friederich Hayek would say. That information is translated into two major market signals, which are embodied in negative prices.

In the short run, negative prices show that there is a local condition of oversupply under which electricity is not an economic good which society is willing to pay for, but an economic bad for which consumers should be compensated. Therefore, negative prices create an economic incentive for consumers to shift their consumption patterns so as to capture the opportunity of being paid, instead of paying, to receive energy….

However, in the long run, negative prices talk to energy producers, not to energy consumers. The emergence of negative prices, although strongly conditioned by demand-side constraints, shows that the generating fleet encompasses too much “rigid” capacity (i.e. too much nuclear and coal-fuelled plants) and too little “flexible” capacity (for example CCGTs or turbo-gas power plants); or that grid interconnections are insufficient to properly exploit the spare, flexible capacity available within a market area.

So far as I know, all of the regional power markets in the United States now allow prices to go negative. The connections between wind power policy and negative prices have politicized the issue a bit in the United States. Benedettini and Stagnaro explain in a straightforward manner why, no matter what you think of renewable energy policies, you ought to favor allowing wholesale power market prices to go negative.

Texas wind power, the ERCOT power market, the Public Utility Commission

From SNL Energy, “Texas utility regulators expect to open investigation on wind ‘cost apportionment’“:

Having seen record wind output of more than 10,000 MW in March, ERCOT in the report also noted that Texas has gone well beyond its 10,000-MW capacity goal and far earlier than the 2025 target established in the state’s Public Utility Regulatory Act. …

And while wind energy continues to boom in Texas, the PUCT has been working with ERCOT on ensuring a reliable power grid amid wholesale prices that are not encouraging new fossil-fuel plant construction.

Perhaps, just perhaps, there is a connection between the “wind energy … boom” and the “wholesale prices that are not encouraging new fossil-fuel plant construction”?

The SNL Energy report noted the PUCT was beginning an investigation into cost apportionment issues surrounding wind energy and the recently completed CREZ transmission line additions.

Power demand in Texas grows more slowly than forecasted

From StateImpact Texas, a joint effort of radio station KUT Austin and KUHF Houston, a report that consumption of electric power in Texas isn’t growing as fast as expected:

As the Texas Public Utility Commission (PUC) considers changing the electricity market so there’s more money to build new power plants, a mystery has popped up: why aren’t Texans using as much electricity as predicted?

“There’s something that’s been going on recently with the forecasts, which affects a lot of things,” said PUC commissioner Kenneth Anderson at the commission’s open meeting last week.

Who Turned the Lights Out?

Anderson said forecasts from the Electric Reliability Council of Texas (ERCOT) had predicted electricity demand would increase in 2013 by 2.1 percent.

In reality?

“It’s been barely one percent, if it’s even hit one percent,” Anderson said.

As the story highlights, this is kind of a big deal. The Texas PUC is contemplating fairly substantive changes to the ERCOT power market design based on projections that power generation capability won’t grow fast enough to meet forecasted future demand. If the forecasts are overstating the problem, maybe regulators need not be quite so nervous.

EIA shows higher wind power output cutting into baseload power generation

The Energy Information Administration’s “Today in Energy” series shows with a couple of charts how growing wind power output in the Southwest Power Pool region is cutting into the income of baseload power plants.

U.S. EIA chart based on Southwest Power Pool data.

The effect matters because baseload power plants tend to have the lowest operating costs. As baseload plants get pushed off the system, more of system capacity will shift to more flexible “load following” plants, which tend to have higher operating costs. Power prices in the Southwest Power Pool and other ISO power markets tend to reflect the operating costs of load following plants, so the effect will be to increase average wholesale power prices.

Wind power advocates sometimes want to claim credit for driving down power prices, and in the short run the addition of wind power can push prices down (especially, of course, if wind power plants have their output subsidized as with the Production Tax Credit). In the long run, as output of cheap-to-run baseload power plants is squeezed from the system, average prices will rise again.

The ERCOT market in Texas faces this same problem — in fact I suspect it is a little further down this path than the Southwest Power Pool — and the state has been struggling over projected resource adequacy concerns on the horizon. Of course, as Texas PUC commission Kenneth Anderson has pointed out, an efficient “energy-only” market with growing consumption should always see resource adequacy problems about four or five years ahead. If it doesn’t see shortages in the future, it implies the system is currently overbuilt. Still, incentives to invest in generation appear weak, wind power capacity additions in Texas are expected to continue, and resource adequacy analysts in ERCOT are nervous.

NRG seeks capacity market for Texas

Michael Giberson

Joe Ragan, a VP at Power generation company NRG, recently opined in the Houston Chronicle in favor of a capacity market for the ERCOT power grid in Texas. A capacity market provides what you might call “being there” payments to generators, whether the generator’s power turns out to be demanded in the market or not.

I was struck by two things while reading the op-ed: first, no mention of the role of wind power in shaping prices and economic conditions for generation in Texas even though ERCOT has the highest wind penetration market-wide in the United States; and second, the way “prices” get invoked.

As any economics student knows, prices are the product of the interaction of supply and demand. In the op-ed, however, prices seem to be something driven by and driving the supply side of the market only. The demand side of the market has “needs” driven by the weather, but apparently not linked to the prices that consumers have to pay.

Admittedly, this way of thinking has 100+ years of tradition behind it in the electric power industry–that’s how it was done under the old cost-of-service, monopoly territory, regulated rate system in the electric power industry.

Texas has been trying something different, with more commercial risk to drive efficiency on the supply side, and potentially high price spikes to motivate an active and engaged consumer side of the market. A capacity market would kill the experiment before it has a chance to pay off.

Al Roth, Matchmaker

Michael Giberson

Stanford’s alumni association magazine has a good article on recent economics Nobelist Al Roth. Several things about the article will trigger resistance among some free market readers, beginning with the title (“The Visible Hand”) and the subhead (A new breed of economist, Alvin Roth brings an engineering sensibility to fixing markets.). Deep into the article, this too: “Thanks to guys like Al Roth and powerful software … we were able to put all our incompatible pairs in there and just hit a button and the computer would spit out the answer.”

In fact just this morning I was just re-reading James Buchanan’s remarks about differences between economics as a science of allocation versus economics as a science of exchange – Buchanan was definitely in the exchange camp – and perhaps Buchanan would wonder whether or not these game-theoretic algorithms constituted a kind of applied economics or perhaps were something more akin to mere logistics tools. But in that article (“General Implications of Subjectivism in Economics”) Buchanan does suggest that game theory, in that it can frame situations from the point of view of economic agents, might constitute a valuable tool for understanding economics as a science of exchange.

But it is clear enough from the Stanford Magazine article that more than logistics is going on in Roth’s efforts. In all of the matching schemes Roth has helped develop, the incentives created for participants are a key constraint. It isn’t a mere matter of minimizing fuels costs for a delivery fleet, Roth is using economics to meddle with the rules of particular kinds of economic systems in order to bring about better arrangements as valued by the participants themselves. These efforts are not about imposing allocations, they are about enabling better exchanges in complex environments.

[HT to Daniel Cole, who draws attention to the dwarf-tossing issues raised at the end of the article.]