How Do Electricity Markets Work?

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Electricity markets coordinate the production, purchase, delivery, and sale of electrical energy. Although electricity is essential to households, businesses, and public services, it cannot usually be stored economically in very large quantities. Supply and demand must therefore remain balanced almost continuously. This physical requirement makes electricity markets different from most other commodity markets.

Why Electricity Is Different

Electricity is produced by generators and transported through transmission and distribution networks before reaching consumers. Unlike oil, natural gas, or coal, electricity cannot normally be stored in large inventories and delivered later without additional technologies such as batteries or pumped-storage hydropower.

At every moment, the quantity of electricity injected into the grid must closely match the quantity withdrawn. A significant imbalance can affect system frequency, reliability, and the safe operation of power plants and networks.

Electricity markets must therefore coordinate economic decisions with the physical operation of the power system.

Main Participants

Electricity markets normally include several groups of participants.

Generators produce electricity using natural gas, coal, nuclear energy, hydropower, wind, solar energy, and other technologies.

Transmission system operators manage high-voltage networks and maintain the balance and reliability of the electricity system.

Distribution companies deliver electricity from the transmission system to homes and businesses.

Retail suppliers purchase electricity and sell it to final consumers.

Consumers create electricity demand through residential, commercial, industrial, and public-sector activities.

Regulators and market operators establish rules, monitor competition, organize trading, and protect system reliability.

The exact structure differs between countries, but these functions exist in most modern electricity systems.

Wholesale Electricity Markets

In wholesale markets, electricity is traded between generators, suppliers, large consumers, and other market participants.

A generator submits an offer indicating how much electricity it is willing to produce and the price at which it is willing to sell. Buyers submit bids representing the quantity they expect to purchase.

The market operator compares supply offers with demand and determines which generating units should operate. Lower-cost generators are generally selected before higher-cost generators, subject to technical and network constraints.

This process is often called economic dispatch.

Day-Ahead Markets

The day-ahead market allows electricity to be scheduled one day before physical delivery.

Generators submit offers for different hours of the following day, while suppliers and large consumers submit demand bids. The market operator then creates a production and consumption schedule.

Day-ahead markets help participants plan their operations and manage expected demand, fuel availability, weather conditions, and generator maintenance.

They also produce hourly electricity prices that provide information about expected system conditions.

Intraday and Real-Time Markets

Actual electricity demand rarely matches the day-ahead forecast exactly. Weather conditions, equipment failures, changes in renewable generation, and unexpected consumer behavior can create differences between scheduled and actual production.

Intraday markets allow participants to adjust their positions closer to the delivery time.

Real-time or balancing markets are used to correct the remaining differences between supply and demand. Generators may be instructed to increase or reduce production, while some consumers may be paid to change their electricity use.

These markets are essential for maintaining the continuous physical balance of the power system.

Electricity Price Formation

Wholesale electricity prices are strongly influenced by the cost of the marginal generator—the last generating unit required to satisfy demand during a particular period.

When demand is low, relatively inexpensive generators may be sufficient. When demand rises, more expensive power plants may be needed, increasing the market price.

Electricity prices can therefore change significantly during the day. They may be higher during periods of strong demand, fuel scarcity, network congestion, or limited renewable generation.

Prices may fall when demand is weak and large quantities of low-marginal-cost renewable electricity are available.

In some markets, prices can occasionally become negative. This may happen when electricity supply is very high, demand is low, and some generators prefer to continue operating rather than shut down.

Network Congestion

Electricity cannot always be transported freely from one location to another. Transmission lines have physical capacity limits.

When a transmission line becomes congested, lower-cost electricity in one region may not be available to consumers in another region. Additional generation may then be required near the area of demand.

As a result, electricity prices may differ between locations. These price differences can indicate where additional transmission capacity, generation, storage, or demand flexibility may be economically valuable.

Capacity and Reliability

Energy-market revenues alone may not always provide sufficient incentives for investment in generation capacity that is used only during periods of exceptionally high demand.

Some electricity systems therefore use capacity mechanisms. These mechanisms pay generators, storage providers, or demand-response participants for being available when the system needs them.

Supporters argue that capacity mechanisms can improve reliability and encourage investment. Critics argue that poorly designed mechanisms may increase costs or support unnecessary capacity.

Their effectiveness depends on market design, regulatory quality, and the characteristics of the electricity system.

Ancillary Services

Electricity systems require more than energy production. They also need services that maintain frequency, voltage, reserves, and system stability.

These are known as ancillary services.

Generators, batteries, flexible consumers, and other resources may provide these services. As electricity systems include more variable renewable energy, fast and flexible ancillary services become increasingly important.

Retail Electricity Markets

Wholesale markets determine the cost of electricity traded between market participants, while retail markets determine how electricity is sold to final consumers.

A consumer’s electricity bill may include:

• Wholesale energy costs
• Transmission charges
• Distribution charges
• Taxes and regulatory charges
• Environmental or renewable-energy costs
• Retail supplier costs

Retail prices may be regulated, market-based, or a combination of both. Some consumers pay fixed prices, while others face time-of-use or dynamic prices that change according to market conditions.

Renewable Energy and Market Design

Wind and solar generation have very low marginal operating costs because they do not require fuel. Their increasing share can reduce wholesale prices during periods of strong renewable output.

However, their production depends on weather conditions. Electricity systems therefore require greater flexibility from storage, transmission networks, flexible generators, demand response, and regional electricity trade.

Market rules must evolve so that these resources receive appropriate incentives for providing energy, capacity, flexibility, and reliability.

Why Electricity Markets Matter

Electricity-market design affects:

• Consumer electricity prices
• Generator revenues
• Investment in new technologies
• Power-system reliability
• Renewable-energy integration
• Energy security
• Emissions reduction
• The economic efficiency of the energy transition

A well-designed market should encourage efficient operation and investment while maintaining reliability and protecting consumers.

Conclusion

Electricity markets connect economic incentives with the physical requirements of the power system. They coordinate generators, networks, suppliers, consumers, and regulators across different time periods.

Because electricity supply and demand must remain continuously balanced, market design plays a central role in determining prices, reliability, investment, and the integration of renewable energy.

Understanding electricity markets is therefore essential for analysing modern energy systems and the economic challenges of the global energy transition.

Mahdi Valizadeh