Carbon Markets / EU ETS

The cap

A regulator sets an absolute ceiling on the emissions of a defined set of installations over a period, and issues exactly that many allowances, each a permit to emit one tonne. Because the number of allowances is fixed, aggregate emissions cannot exceed the cap however the economy behaves. That is the instrument's defining property and its main selling point: the environmental outcome is decided in advance, and the cost of reaching it is what gets discovered.

The trade

Allowances are transferable. An installation that can cut a tonne for less than the going price does so and sells the allowance it no longer needs; one whose abatement is dearer buys instead. Trading therefore routes the reduction to wherever it is cheapest, and in equilibrium the allowance price settles at the marginal cost of the last tonne the cap forces out. That price is the system's product — a single, economy-wide number for what carbon is worth — and it is why a cap-and-trade price can be fed into a power plant's dispatch decision or a project's investment case as an ordinary cost.

Quantity or price

The alternative is a carbon tax, which fixes the price and leaves the quantity to follow. The choice is about which uncertainty a society prefers to bear. A cap guarantees the tonnes but lets the price swing with the business cycle, fuel prices and policy expectations; a tax guarantees the cost but not the outcome. Most real systems, the EU ETS included, hedge the choice: a cap at the core, with price-responsive supply adjustments, reserves and cost-containment provisions grafted on to keep the price within a tolerable range. Reading those provisions is reading the compromise a jurisdiction has made between the two.

Allocation and the compliance year

Allowances enter the market by auction or by free allocation; the split decides who receives the scarcity rent that a binding cap creates, and is the most contested design choice in any system. Once issued they are held in a registry, banked across years and traded freely. Each covered installation monitors its emissions, reports them by 31 March, and by 30 September must surrender allowances equal to the previous year's verified tonnes. Falling short costs €100 per tonne, indexed to inflation, and the missing allowances must still be surrendered — so the penalty is a deterrent, not a price ceiling.

Why it matters for power

Electricity is where cap and trade bites hardest and fastest. Generators face the allowance price as a marginal cost on every megawatt-hour from fossil plant, whether they bought the allowance or were given it, because the alternative is to sell it. The carbon price therefore rewrites the merit order between coal and gas, lifts the wholesale price whenever a fossil plant is marginal, and sets the value of everything that displaces one. The EU ETS is the largest such system in operation, and the rest of this page is about how its design produces — and sometimes distorts — that signal.

The cap and its trajectory

An absolute, EU-wide ceiling on covered emissions declines each year by the linear reduction factor, tightened with every reform round to track the bloc's climate targets. The cap's credibility — the belief that it will keep falling regardless of the price — is the asset the entire market prices.

Allocation: auction vs. free

Auctioning on the common platform is the default and the power sector's reality — generators buy every allowance. Industry at carbon-leakage risk still receives free allocation against product benchmarks, a shrinking carve-out as CBAM phases in to price embedded carbon at the border instead.

The Market Stability Reserve

The MSR absorbs allowances from auction volumes when the surplus in circulation is high and releases them when it is scarce — with excess reserve holdings invalidated outright. It converted a decade-long surplus overhang into scarcity and made the supply curve policy-responsive: the ETS's single most consequential retrofit.

Compliance cycle and banking

Installations surrender allowances annually against verified emissions; unlimited banking lets allowances travel across years. Banking is what makes the EUA an asset with a forward curve — today's price embeds expectations about scarcity decades out.

Scope

Power and heat, energy-intensive industry, intra-European aviation and, progressively, maritime transport sit inside the system. Each scope extension changes the demand structure — shipping brought a new class of compliance buyers with no allocation history.

ETS2

A separate, parallel trading system covers fuels for buildings and road transport upstream at the supplier level, with its own cap, its own price and a price-triggered reserve mechanism intended to soften early volatility. Keeping it apart from ETS1 was a deliberate choice to protect both systems' price formation — and their politics.

One asset, several instruments

Every product below settles into the same unit: an EUA, an entry in the Union Registry entitling its holder to emit one tonne of CO₂-equivalent. What differs is timing and counterparty. A spot trade transfers allowances now. A future obliges physical delivery at expiry, months or years ahead, through a clearing house that guarantees both sides. An option is a right over a future. A forward is the same promise made bilaterally, without a clearing house in the middle. Since 2018, EUAs and derivatives on them have been financial instruments under MiFID II, which is why the venues are regulated markets, why position limits, reporting and market-abuse rules apply, and why ESMA publishes an annual report on the market's structure.

Primary market: the auctions

New supply reaches the market almost entirely through auctions run by EEX as the EU's common auction platform, currently contracted to the end of 2026, on behalf of 25 member states, the EEA EFTA states and the Innovation and Modernisation Funds. Common-platform auctions run on Mondays, Tuesdays and Thursdays; Germany auctions its own share on Fridays and Poland every other Wednesday, both also on EEX. The format is deliberately simple — a single round, sealed bids in lots of 500, a bidding window of at least two hours, and one uniform clearing price at which cumulative demand meets the volume offered — so that a small emitter can participate without a trading desk. In 2024 the platform sold 599 million allowances for €39 billion. Participation is thin and intermediated: 20 to 25 bidders per auction, with around 90% of allowances taken by ten firms, largely banks and investment firms buying on behalf of clients. The Market Stability Reserve acts on this channel, withdrawing from or adding to auction volumes according to the surplus in circulation.

Futures: where the price is made

The reference price for European carbon is not the auction and not the spot market but the front-December futures contract on ICE Endex in Amsterdam. Each contract is 1,000 allowances, quoted in euros and cents per tonne; December contracts are listed up to seven years out, alongside quarterly and monthly expiries, and trading ceases on the last Monday of the contract month, after which open positions deliver physically into Union Registry accounts through ICE Clear Europe. EEX lists its own EUA futures and options, cleared through ECC. Between them the two venues carry 99% of on-venue transactions. Futures are the market: 77% of on-venue volume in 2024 and 45% of open interest, with forwards a further 30% and options 19%. Total activity that year was 13.7 billion tonnes, roughly nine times annual auction supply, of which 12.6 billion traded on venue for €644 billion. Options, almost entirely written on the futures, grew 65% to 2.9 billion tonnes as the market's uncertainty about the reform path became something worth paying for.

Spot, and why it is thin

Genuine spot trading exists — EEX runs a spot market in EUAs and aviation allowances, and ICE's EUA Daily Future is a prompt-delivered contract that serves the same purpose — but it is a fraction of the futures market. The reason is structural. A compliance buyer needs allowances by the September surrender date, not today, and a December future delivers them with no funding cost until expiry and no registry transfer to manage in between. A utility hedging power it has sold three years forward needs carbon three years forward, and a future is the only instrument that provides it. The spread between spot and the December contract is therefore mostly a cost of carry, and when it inverts it is read as a signal of near-term tightness. Over-the-counter trading, at 8–10% of volume and mostly futures-style forwards, plays the same role at the margin: bespoke sizes and tenors, brokered rather than screened, and reported under EMIR rather than cleared.

Who trades

The compliance entities the system was designed for are not its main traders. In 2024 the financial sector accounted for 79% of on-venue volume: investment firms and credit institutions 7.9 billion tonnes, investment funds a further 2.0 billion. Non-financial companies traded 17%. The picture in positions is different again — investment firms and banks held 51% of all positions, funds only 6% — which reflects the intermediation the design relies on: banks buy at auction and warehouse allowances for clients, utilities hold large hedged books, and funds turn positions over rather than hold them. Nearly three-quarters of on-venue volume comes from entities outside the EEA, chiefly US and UK. Whether financial participation stabilises the price by supplying liquidity or amplifies it by chasing momentum is the standing argument of ETS market design, and it is the question ESMA's reporting regime exists to answer.

Delivery and the registry

Every instrument above resolves into a transfer in the Union Registry, the single ledger where allowances exist. Futures deliver into registry accounts after expiry; spot trades transfer within days; surrender is a registry transaction against verified emissions, due by 30 September each year since the 2023 reform moved it from April. Banking is unlimited, so an allowance bought at auction in one year can be surrendered in any later one, and the registry is where that optionality lives. It is also why the market is unusually clean at the margin: there is no basis risk between the financial instrument and the physical asset, because the physical asset is itself an account entry.

Adjacent units

Three related products trade alongside EUAs and are easily confused with them. Aviation allowances (EUAAs) were a separate unit; since January 2025 aircraft operators receive general EUAs instead, existing EUAAs remain valid and interchangeable, and they stop being issued after 2027. UK allowances (UKAs) belong to the UK ETS, auctioned and traded on ICE Futures Europe in London, and priced at a persistent discount to EUAs. ETS2 allowances are a distinct unit for buildings and road transport, for which ICE listed EUA 2 futures in May 2025, ahead of any primary market. None of the three is fungible with an EUA in the registry, and the design lesson in all of them is the same: a separate unit is a separate market, with its own liquidity to build.

The abatement anchor

In the short run the price gravitates toward the cost of the marginal abatement it must trigger — historically the coal-to-gas fuel switch in power. As coal exits the merit order, the marginal abatement migrates toward industrial measures and demand response, changing which fundamentals move the price.

Expectations rule

Because allowances bank, today's price is a claim on future scarcity. Reform announcements, target revisions and rebasing decisions move the market more than any single year's emissions outcome — the EUA trades like policy, because it is.

Utility hedging demand

Generators selling power forward buy allowances forward to lock the carbon leg of their margin — a structural, price-insensitive demand flow tied to the power hedging cycle. Shifts in hedging behaviour propagate directly into EUA term structure.

Financial participation

Funds and dealers carry inventory, provide liquidity and connect the EUA to macro conditions — rates, energy complexes, risk appetite. Periodic political anxiety about 'speculation' has repeatedly run into the same finding: intermediation deepens the market compliance players need.

Supply as a feedback loop

With the MSR, realised surplus changes future auction volumes: weak demand today tightens supply tomorrow. The design intentionally dampens surplus cycles — and makes modelling the system a fixed-point exercise rather than a simple balance.

Interacting policies

Renewables targets, efficiency programmes and national coal phase-outs reduce covered emissions without the carbon price doing the work — the waterbed effect. MSR invalidation partially re-tightens the cap in response, one of the subtler pieces of design reasoning in the system.

Pass-through into power prices

Fossil generators bid their fuel-plus-carbon marginal cost, so whenever fossil plant is price-setting, the carbon price flows into the wholesale power price — including into the infra-marginal rents of every low-carbon generator. Pass-through is the mechanism by which the EUA finances clean investment without a single subsidy.

Clean spreads

The clean spark spread (gas) and clean dark spread (coal) — power price minus fuel and carbon cost per MWh — are the operating signals of thermal generation. Their crossover point defines the fuel-switch band where the carbon price directly re-orders dispatch.

Merit-order reordering

A rising carbon price penalises high-emission plant disproportionately, pushing coal and lignite up the merit order past efficient gas. This within-fossil reordering was the ETS's first observable success — and its progress is self-erasing as the plants it displaces retire.

Carbon in scarcity and capture

Carbon costs raise the price level in fossil-set hours while leaving renewable-set hours untouched — widening the spread that batteries arbitrage and shaping renewable capture rates. Carbon-price scenarios are therefore embedded in every serious storage and PPA valuation.

Investment-horizon signal

Project finance discounts the EUA forward curve, not the spot: long-term price credibility, MSR behaviour and target legislation matter more for a 2035 asset than today's print. The carbon market's design quality is measured in the cost of capital of low-carbon projects.

Design frictions

Capacity-mechanism emission limits, national carbon price floors and border adjustment interact with the ETS in ways not always intended by any single designer — the boundary between carbon and power market design is where the next decade's tensions accumulate.

Cap and compliance

The emissions cap limits the quantity of allowances available. Covered installations surrender allowances against verified emissions, creating demand for EU Allowances and an opportunity cost for emitting generation.

Primary and secondary markets

Allowances enter the market through auctions and free allocation. Spot, futures and options trading supports compliance and hedging, with ICE and EEX among the principal organised venues.

Market Stability Reserve

The MSR adjusts auction supply according to the allowance surplus, reducing persistent oversupply while introducing a rule-based link between circulation and future scarcity.

Power-sector pass-through

Generators include the carbon opportunity cost in short-run marginal cost. Carbon therefore affects the merit order, wholesale prices and the relative economics of coal, gas and low-carbon generation.

Clean spreads

Clean dark and clean spark spreads combine electricity, fuel, efficiency and carbon prices. They are central indicators for dispatch incentives, hedging and expected thermal profitability.

Investment signal

A credible long-term carbon constraint supports low-carbon investment, but its effect interacts with renewable support, capacity mechanisms, network constraints and expectations about future policy.