Module 8 — A Control-Theoretic Perspective on Electricity Markets
Lesson 2 of 8
Prices as Signals
Learning objectives
By the end of this lesson you should be able to:
- Understand how prices communicate information within markets.
- Explain how prices influence the behaviour of buyers and sellers.
- Distinguish between prices as incentives and prices as commands.
- Recognise why prices can coordinate decisions without central direction.
- Appreciate both the strengths and limitations of price-based coordination.
Introduction
In the previous lesson, we saw that markets help coordinate the decisions of many independent participants.
But how does this coordination actually occur?
The answer lies largely in prices.
When people hear the word price, they often think simply about the amount of money paid for a good or service.
However, economists often view prices in a broader way.
Prices communicate information.
They influence behaviour.
They help coordinate decisions between buyers and sellers.
For this reason, prices are often described as signals.
What is a signal?
A signal is information that influences decision-making.
We encounter signals throughout everyday life.
Examples include:
- traffic lights,
- road signs,
- weather forecasts,
- warning alarms,
- speed limits.
These signals do not physically force people to act.
Instead, they provide information that influences behaviour.
Prices perform a similar role in markets.
Rather than instructing participants what to do, prices provide information that participants use when making their own decisions.
Prices communicate scarcity
One of the most important pieces of information conveyed by prices is scarcity.
When something becomes relatively scarce, its price often rises.
When it becomes more abundant, its price often falls.
Consider bottled water.
On an ordinary day, bottled water may be inexpensive because supply is plentiful.
During a major sporting event or following a natural disaster, demand may increase sharply while available supply remains limited.
Prices often rise.
The higher price reflects the changing balance between supply and demand.
Participants do not need to know every detail about why conditions have changed.
The price itself provides a useful summary of the changing situation.
Prices influence behaviour
Prices do not simply communicate information.
They also influence behaviour.
Higher prices typically encourage producers to increase supply where possible.
At the same time, they encourage consumers to consider whether purchasing remains worthwhile.
Lower prices often have the opposite effect.
They encourage greater consumption while reducing incentives for additional production.
Through these individual responses, prices help markets adapt to changing conditions.
Signals, not commands
An important feature of prices is that they influence rather than dictate behaviour.
A high price does not force someone to stop buying.
A low price does not require someone to make a purchase.
Participants remain free to make their own decisions.
Different people may respond differently to the same price depending on:
- their preferences,
- available alternatives,
- financial circumstances,
- urgency.
Prices therefore coordinate behaviour without removing individual choice.
A simple example
Imagine a coffee shop.
On a quiet weekday afternoon, the shop has spare capacity.
Customers can be served quickly, and there is little competition for tables.
Now imagine arriving on a busy Saturday morning.
Demand is much higher.
If the shop chose to increase prices during this period, some customers might decide to visit later, while others would still purchase their coffee.
The higher price would not guarantee a particular outcome, but it would influence behaviour by encouraging some demand to shift away from the busiest period.
Many industries use similar approaches to balance changing levels of supply and demand.
Dynamic pricing
Some markets allow prices to change over time.
This is known as dynamic pricing.
Examples include:
- airline tickets,
- hotel rooms,
- ride-sharing services,
- event tickets.
Prices often vary according to:
- demand,
- availability,
- expected future conditions,
- remaining capacity.
Dynamic pricing allows market signals to adapt as circumstances change rather than remaining fixed.
Prices summarise information
One of the remarkable features of markets is that prices summarise large amounts of dispersed information.
A producer does not need to know every customer's preferences.
A consumer does not need detailed knowledge of every producer's costs.
Instead, much of this information becomes reflected in market prices.
Economist Friedrich Hayek famously argued that prices allow knowledge dispersed across society to be communicated in a highly efficient way.
Rather than requiring every participant to understand the entire system, individuals can often make effective decisions using the information conveyed by prices.
Prices and electricity
Electricity markets also rely heavily on prices.
Prices may influence decisions such as:
- when generators produce electricity,
- when consumers use electricity,
- when batteries charge or discharge,
- where investment occurs.
However, electricity systems introduce additional challenges.
Unlike many other goods, electricity must remain continuously balanced, and every market decision must remain consistent with the physical operation of the network.
This means electricity prices often serve several purposes simultaneously.
Understanding these additional roles is one reason electricity market design is such an active area of research.
Prices are only one source of information
Although prices are powerful coordination signals, they are not the only information available to decision-makers.
Participants may also consider:
- engineering constraints,
- contractual obligations,
- regulations,
- forecasts,
- operational requirements,
- customer preferences.
In many practical systems, prices operate alongside these other forms of information rather than replacing them.
Markets therefore combine economic signals with broader institutional and technical arrangements.
A key insight
Prices are more than monetary values.
They communicate information about changing market conditions and influence the behaviour of independent participants.
Rather than directing decisions through central commands, prices allow individuals to respond to changing circumstances using their own knowledge, objectives and preferences.
For this reason, prices can be viewed as signals that help coordinate activity across a market.
Key takeaways
- Prices communicate information as well as determining payment.
- One of the main functions of prices is to signal relative scarcity.
- Price changes influence the behaviour of buyers and sellers without removing individual choice.
- Dynamic pricing allows signals to adapt to changing market conditions.
- Prices summarise information dispersed across many different participants.
- Electricity markets also use prices to influence behaviour, although they must operate within additional physical and operational constraints.
- Prices are one source of information among many that participants may consider when making decisions.
Looking ahead
In the previous module, we saw that modern electricity systems are becoming increasingly digital, observable and information-rich.
If prices influence behaviour, an interesting question naturally follows:
How does a market know what information to incorporate into its prices?
In the next lesson, we introduce the concepts of state, feedback and observability, examining how dynamic systems gather information about their own behaviour and use that information to support coordinated decision-making.