Electricity has to be bought before it can be billed and generated before it can be used—but those two processes happen so close together that Singapore runs a market almost in real time.
At the centre is the Singapore Wholesale Electricity Market, operated by the Energy Market Company, or EMC, under the National Electricity Market of Singapore framework.
Generators submit offers to supply electricity. Demand forecasts indicate how much power the system is expected to need. The Market Clearing Engine evaluates the offers together with transmission constraints and system requirements, calculates which registered facilities should be scheduled and determines market prices.
EMC’s current market material defines one trading period as half an hour. The Market Clearing Engine runs every half hour, giving Singapore 48 trading periods each day. Market prices and dispatch quantities for energy, reserves and regulation are calculated about five minutes before the start of each half-hour trading period.
The operating chain is: forecast demand → generators submit offers → market engine models the grid → energy, reserve and regulation are co-optimised → dispatch quantities and nodal prices are calculated → Uniform Singapore Energy Price is derived → wholesale purchases are settled → EMA’s Power System Operator manages the actual grid continuously in real time.
Quick answer: what does the wholesale market decide?
- Which controllable generation facilities are scheduled: according to offers, demand and system constraints.
- How much each scheduled facility should produce: through dispatch quantities calculated for the trading period.
- Energy prices: including nodal energy prices and the Uniform Singapore Energy Price used in settlement.
- Reserve and regulation quantities and prices: so the market procures flexibility as well as energy.
- Settlement: calculating what market participants owe or are owed after the trading period.
1. Electricity cannot be stored in the market like ordinary inventory
A warehouse can buy goods today and sell them weeks later.
An electricity system must keep generation and consumption balanced continuously. Batteries can shift some energy through time, but the power system as a whole still has to match supply and load at every moment.
The wholesale market therefore operates close to physical delivery. Its schedule is a plan for electricity that will be produced and consumed almost immediately.
2. Generator offers create the supply curve
Registered generation facilities participating in the dispatch market submit offers under the Market Rules.
An offer tells the market how much electricity the facility is prepared to supply at different price levels and under the applicable technical conditions.
When many generators submit offers, the market engine can compare their available quantities and prices while still respecting what the transmission system can physically carry.
3. Demand is forecast because the market clears before the half hour begins
EMC cannot wait until the end of a trading period to discover how much power Singapore needed.
EMA’s Power System Operator develops a forecast of half-hourly average system demand, and EMC also produces market forecast schedules that become more frequent as delivery approaches.
The market therefore clears against the best available near-term picture rather than perfect knowledge of the future.
4. The Market Clearing Engine is more than a cheapest-generator list
If electricity could move anywhere in Singapore without losses or network limits, dispatch could be reduced to a simple ranking of generation offers.
The actual grid has transmission constraints, electrical losses and security requirements.
The Market Clearing Engine therefore uses security-constrained dispatch. It calculates an economically efficient schedule that is also consistent with the network model and the power system’s operating requirements.
5. Nodal pricing makes grid location visible to the market
Electricity injected at one part of the network is not always identical in system value to electricity injected somewhere else.
Transmission constraints and losses can create different nodal energy prices at different market network nodes.
Locational pricing therefore lets the market engine represent the physical network instead of pretending every generator is connected to one lossless copper plate.
6. The Uniform Singapore Energy Price creates one settlement reference for load
EMC defines the Uniform Singapore Energy Price, or USEP, as the weighted average of nodal prices at all off-take nodes in each half hour.
Generation companies are paid according to the applicable nodal-pricing arrangements, while USEP provides the uniform energy-price reference used for settlement at the Singapore hub.
The market therefore preserves locational signals on the generation side while creating a common energy reference for wholesale consumption settlement.
7. Wholesale Electricity Price is broader than USEP
EMC defines the Wholesale Electricity Price, or WEP, as the net purchase price paid by retailers in the wholesale market.
It includes USEP together with regulation allocation, uplift charges and market or system-operator fees under the prevailing market rules.
That is why “wholesale electricity price” and “energy price” are not always the same number.
8. Forty-eight trading periods make the market responsive to the day
Electricity demand is different at 3.00am, 9.00am and 4.00pm.
Fuel availability, plant outages and solar production also change.
Half-hour trading periods let the market update schedules and prices as those conditions change instead of setting one price for the entire day.
9. Near-real-time calculation happens five minutes before delivery
EMC states that market prices and dispatch quantities are calculated five minutes before each half-hour trading period begins.
This lets the market use recent generator offers, demand-response bids and current power-system conditions.
The schedule is therefore neither a day-ahead promise nor a second-by-second control signal. It sits between longer-term forecasting and real-time system operation.
10. Energy, reserve and regulation are co-optimised
Singapore’s market does not procure only megawatt-hours of energy.
The system also needs reserve capacity that can respond to significant contingencies and regulation capability that can help track short-term changes in demand and generation.
The Market Clearing Engine co-optimises energy, reserve and regulation so a generator’s capacity cannot be counted independently in several incompatible jobs at the same moment.
11. A cheap generator may not be fully scheduled if the grid cannot use all of its output
Suppose one generation facility offers low-priced electricity but transmission conditions limit how much additional output can be moved safely through its part of the network.
The market engine may need to schedule a different combination of facilities even if another generator’s offer price is higher.
Security-constrained dispatch therefore prices the usable system, not an imaginary market without wires.
12. Transmission losses also have to appear in settlement
Not every unit of electricity injected into the network reaches the customer as useful delivered energy because conductors and equipment have electrical losses.
EMA uses Transmission Loss Factors in settlement and electricity-charge calculations to account for transmission losses and unaccounted-for energy.
EMA revised the methodology with effect from 1 April 2026.
The accounting system therefore keeps the energy ledger aligned with the physical fact that the grid itself consumes a small part of what flows through it.
13. Market dispatch and physical grid control are separate jobs
EMC runs the market and produces dispatch schedules.
EMA’s Power System Operator runs the physical power system in real time.
PSO monitors system frequency, voltage, generation and network flows and works with market participants to keep the power system stable.
The distinction prevents a market price calculation from being mistaken for the safety-critical control of the actual electricity network.
14. Automatic Generation Control closes the seconds-level gap
Actual electricity consumption changes continuously inside each half-hour trading period.
EMA states that Automatic Generation Control monitors electricity demand and adjusts generator output every few seconds to match those dynamic changes.
The wholesale schedule therefore sets the economic operating point, while real-time control keeps physical supply and demand aligned around it.
15. Retail electricity prices are downstream of the wholesale market
Electricity retailers buy electricity from the wholesale market and sell plans to contestable consumers.
Consumers on the regulated tariff receive electricity through the regulated tariff framework rather than paying the raw half-hour wholesale price directly.
The wholesale market therefore is one price layer beneath retail contracts, tariff structures, hedges, network charges and other consumer-facing components.
16. Wholesale prices can move sharply when the supply cushion tightens
If demand is high, fuel is constrained or several generating facilities are unavailable, the market may need increasingly expensive offers to satisfy the forecast load and system requirements.
Wholesale prices can therefore become volatile even though the physical electricity delivered through the wall socket looks identical.
The price is signalling scarcity in production and system flexibility, not a change in the quality of the electrons.
17. The Temporary Price Cap is a circuit breaker, not a permanent fixed price
EMA introduced the Temporary Price Cap framework in 2023 to mitigate periods of high and sustained wholesale market volatility.
EMC’s current price pages publish reference uncapped prices when the TPC is in effect.
The mechanism therefore acts as a market-stability circuit breaker under defined conditions rather than replacing competitive wholesale pricing with one permanent administered price.
18. Public market data makes the price formation visible
EMC publishes real-time and final market information, including USEP, nodal prices, reserve prices, regulation prices, WEP and market trading reports.
Daily trading reports for late August and early September 2026 are publicly available through the NEMS portal.
The wholesale market therefore leaves an evidence trail that analysts, market participants and the public can inspect after each trading period.
19. A worked example: demand rises before an afternoon peak
Imagine forecast demand for the next half hour rises as commercial cooling and industrial loads remain high.
Generators have submitted offers showing how much capacity they can provide at different prices. The Market Clearing Engine combines those offers with the forecast, reserve and regulation requirements and the network model. It schedules the least-cost feasible combination consistent with system constraints, calculates nodal prices and derives the half-hour USEP. Retailers are settled through the wholesale market while PSO continuously corrects physical deviations as real demand evolves.
The price and the power move together, but they are governed by two connected control systems.
20. Common misconceptions
Misconception: Singapore chooses one cheapest power station and runs it all day.
No. dispatch is recalculated for half-hour trading periods and is constrained by demand, network and system-security requirements.
Misconception: USEP is the same thing as every household’s electricity price.
No. consumer tariffs and retail plans include other commercial, regulatory and network layers.
Misconception: EMC physically controls every generator second by second.
No. EMC operates the wholesale market; EMA’s Power System Operator owns real-time system operation.
Misconception: All generators receive one identical nodal price.
No. NEMS uses locational nodal pricing; USEP is a weighted average at off-take nodes for settlement purposes.
Misconception: Electricity market pricing can ignore the grid because electricity is fungible.
No. transmission constraints, losses, reserves and regulation are part of the clearing problem.
21. The deeper idea: the market converts scarcity into instructions before physics has to solve it
The physical grid does not care which generator is cheap.
It cares that voltage, flows and supply-demand balance remain safe.
The wholesale market sits one layer above that physics. It asks which combination of controllable resources can satisfy the expected system requirement at the lowest feasible market cost, given the grid that actually exists.
Then the real-time operator takes the schedule and keeps the physical system inside its safety envelope as reality deviates from the forecast.
The price is therefore not an abstract number floating above the power system. It is the market’s attempt to tell thousands of megawatts where scarcity exists before the grid has to discover that scarcity as a physical emergency.