Mexico's Wholesale Electricity Market and CENACE: How Power Dispatch Works

An Architecture of Decisions Made Every Hour

Every hour of every day, thousands of variables converge to determine which generation plant operates in Mexico and at what price that energy is settled. This is not an arbitrary decision: it is the result of an optimization algorithm that ranks the country's available capacity by generation cost and compares it against demand that shifts second by second. The mechanism that makes this nationwide coordination possible is called the Wholesale Electricity Market (MEM, for its Spanish acronym); the body that operates it is the National Energy Control Center (CENACE). Understanding its design is the foundation for grasping why electricity costs what it does in Mexico, and what determines the economic viability of any generation project in the country.

CENACE: The System's Technical Arbiter

CENACE is a decentralized public body in the energy sector, created by the 2013 constitutional reform and fully operational since 2016. Its mandate is twofold: to operate the National Electric System (SEN) according to security and reliability standards, and to administer the wholesale market impartially with respect to all commercial participants.

Before the reform, those functions were concentrated in the Federal Electricity Commission (CFE) as a vertically integrated utility. The functional separation that gave rise to CENACE addressed a classic design problem in network economics: the same actor cannot simultaneously be the system operator and a commercial player with a stake in the dispatch outcome. Mexico's solution followed the model of Independent System Operators already running in reference markets such as ERCOT in Texas and the California ISO.

CENACE does not buy or sell energy. It holds no generation assets. Its role is to coordinate dispatch, calculate settlement prices, and publish real-time price signals to guide market participants' decisions.

Who Participates in the MEM

The Wholesale Electricity Market groups participants with differentiated roles under open-access rules for the national transmission grid.

Generators and Suppliers

Any plant with installed capacity above 0.5 MW can participate as a generator. The universe includes CFE's generation subsidiaries, independent power producers (PIEs) with pre-reform contracts, and new private generators licensed by the Energy Regulatory Commission (CRE). Basic services suppliers (primarily CFE Suministrador de Servicios Básicos) acquire energy in the market to serve regulated users; qualified suppliers serve large consumers who opted out of the regulated tariff scheme.

Qualified Users

Consumers with demand above 1 MW can participate directly in the market through Electricity Coverage Contracts (CCEs) with generators or by purchasing energy in the short-term market. This category ranges from mining or automotive industrial complexes to data centers and university campuses with active energy management.

Economic Dispatch: The Principle That Orders the System

The operational core of the MEM is economic dispatch by merit order. Given a projected demand for a given hour, CENACE ranks available plants from lowest to highest variable generation cost and dispatches them in that order until demand is covered. The last plant the system needs to balance the load curve sets the reference price for that hour.

This logic minimizes total system cost in each settlement period. A combined-cycle natural gas plant displaces a fuel-oil thermal unit. A wind or solar plant, with variable cost near zero, has dispatch priority when available. Hydroelectric reservoirs follow a different logic: their water resource carries an opportunity value that varies with rainfall forecasts and expected demand.

The U.S. Energy Information Administration noted that the design of Mexico's new electricity markets sought to reduce system costs and develop new generation capacity through competitive price signals that would direct investment toward the most efficient resources. CENACE's algorithm also incorporates network constraints: the physical capacity of transmission lines limits how much energy can flow between regions, and when that capacity is insufficient, congestion appears as the primary source of price differences across system nodes.

The Local Marginal Price: Three Components That Define the Real Cost

The Short-Term Energy Market settles transactions through the Local Marginal Price (PML), a price that varies by node on the transmission network and by hour of the day. The PML has three additive components:

Energy component. Reflects the cost of a megawatt-hour under uncongested network conditions: the price of the system's marginal plant at that moment. This is the dominant component under normal operating conditions.

Congestion component. Arises when transmission capacity between zones is insufficient to export cheaper energy to where it is needed. The congested zone draws on more expensive local generation, pushing the price above the system average. This is the most volatile component of the PML and the one that generates the largest price differences across regions.

Losses component. Transmission networks lose a fraction of the energy transported due to resistive effects. This component adjusts the price to reflect the additional energy that must be generated to compensate for those physical losses at each node.

The hourly publication of PMLs by node in CENACE's Market Information System (SIM) enables generators, qualified users, and investors to project returns, design contracting strategies, and evaluate the optimal location for new projects.

Market Layers: Different Time Horizons

The MEM operates with settlement layers across different time horizons. The Day-Ahead Market (MDA) runs on the afternoon before dispatch: participants submit bids for each hour of the following day and CENACE publishes the schedule and prices before midnight; most of the system's energy is settled here. The Real-Time Market (MTR) operates in five-minute windows and corrects deviations between the MDA schedule and actual operations: an unplanned plant outage, an unanticipated demand spike, the variability of solar generation on an overcast day. Beyond energy, CENACE procures through separate mechanisms the Ancillary Services the system requires: frequency regulation, spinning reserve, and voltage control, a technically specialized but financially relevant segment for high-response-speed technologies.

The International Context: What Mature Markets Teach

The MEM's design follows the model of reference electricity markets in North America and Europe. The International Energy Agency concluded that Mexico's energy reform was "set to revitalise a weakened sector and boost the economy" by introducing competition in generation and regulated openness in network infrastructure.

The closest structural reference is PJM Interconnection in the northeastern United States, the world's largest market by load served, which operates on the same basic principles: merit-order dispatch, localized marginal prices, and regulated access to the transmission grid as a natural monopoly. IMCO has noted in its analysis of the electricity market in Mexico that the MEM's regulatory design contains technically sound elements, but that effective operation requires a consistent regulatory trajectory for price signals to fulfill their function: directing investment toward the most efficient and lowest-cost resources for the system as a whole. What distinguishes the Mexican case in comparative perspective is the scale of CFE's historical weight across the entire value chain and the complexity of the transition from a fully integrated system toward one with genuine competition in generation.

Toward a More Functional Market: Areas for Institutional Development

The MEM has proven technical foundations. Merit-order dispatch, hourly PML calculation by node, and functional separation between system operation and commercial participation are robust design elements, validated in mature markets across three continents. The path toward consolidation runs through concrete dimensions within reach of existing institutions.

Transmission infrastructure. Node congestion is the primary source of distortion in PMLs and the factor that most undermines the locational signal for new investment. Planned expansion of the National Transmission Grid reduces congestion rents and allows prices to reflect the true cost of the generation fleet with greater fidelity.

Firm capacity signals. The MEM today operates primarily as an energy market. Mechanisms that signal in advance the firm capacity the system will need in the medium term reduce the risk of shortfalls during peak hours and lower the financing cost of new generation projects by providing certainty over future revenues, an instrument that markets such as PJM and the UK's Capacity Market have developed with different designs but the same objective.

Active demand response. Qualified users capable of modulating their consumption in response to hourly prices are, in mature systems, a flexibility resource as valuable as a backup plant. Demand management instruments connected to the MTR expand the system's room to maneuver and can reduce the marginal price during critical hours.

Data openness. CENACE's SIM already publishes significant volumes of information. Moving toward accessible programming interfaces and long historical series would open market analysis to researchers, regulators, and smaller participants, strengthening the knowledge base that underpins any future regulatory adjustment.

The Wholesale Electricity Market is, at its core, a mechanism for decentralized coordination of a good that cannot be easily stored, that tolerates no interruption, and that the national economy requires at a competitive price. The maturation of that mechanism, with stable rules, transparent operation, and reliable price signals, is a structural condition for Mexico's energy development over the medium and long term.

Frequently Asked Questions

What is Mexico's Wholesale Electricity Market (MEM)?

The MEM is the wholesale electricity market where generators, suppliers, and qualified users buy and sell energy based on market prices. It is administered by CENACE and operates through mechanisms of economic dispatch, hourly settlement, and Local Marginal Prices (PMLs) differentiated by network node.

How does CENACE work in Mexico?

CENACE is the independent body that operates the National Electric System and administers the Wholesale Electricity Market. It determines the dispatch order for generating plants, calculates hourly settlement prices, and publishes real-time market price signals. It does not buy or sell energy.

What is the Local Marginal Price (PML) of electricity?

The PML is the energy settlement price at each node on the transmission network for each hour of the day. It has three parts: the energy component (cost of the system's marginal plant), the congestion component (price differences due to transmission constraints between regions), and the losses component (additional energy to compensate for physical losses on the network).

What is economic dispatch of electricity?

It is the mechanism by which CENACE ranks generation plants from lowest to highest variable cost and dispatches them in that order until projected demand is covered. It minimizes total system cost in each period and prioritizes low variable-cost sources, such as wind and solar, when available.

What is the difference between the Day-Ahead Market and the Real-Time Market?

The Day-Ahead Market (MDA) runs on the afternoon before dispatch and schedules most of the system's energy for each hour of the following day. The Real-Time Market (MTR) operates in five-minute windows throughout the day and corrects deviations between that schedule and actual operations, reflecting supply and demand conditions in near real time.

Fuentes:

• https://www.cenace.gob.mx/QuienesSomos.aspx
• https://www.cenace.gob.mx/Paginas/SIM/MercadoCP.aspx
• https://www.cenace.gob.mx/Paginas/Publicas/Transparencia/MEM.aspx?tema_rec=Entidades+e+Integrantes+del+MEM
• https://www.eia.gov/todayinenergy/detail.php?id=26932
• https://imco.org.mx/mercado-electrico-en-mexico-nuevas-reglas-y-camino-regulatorio-pendiente/
• https://www.iea.org/news/mexicos-energy-reform-is-set-to-revitalise-an-ailing-sector-and-boost-the-economy-iea-report-says