CASE STUDY
Rebuilding the EU ETS1 Calculator with River
How Climact replaced a legacy Excel model with a structured, auditable engine, ready for EU legislative negotiations in 2026.
CLIENT
Climact SA
SECTOR
Climate Policy & Regulatory Analysis
DELIVERABLE
EU ETS1 scenario calculator, 2020–2040
30+
policy levers modeled
20yr
model horizon
15
model users
A high-stakes model on a robust foundation
The EU Emissions Trading System (ETS1) is one of Europe's most consequential climate policy instruments. In 2025, Climact, a Brussels-based climate consultancy, was engaged to build a calculator that lets policymakers, NGOs, and analysts test how different design choices affect the EU's ability to meet its 2030 and 2040 climate targets.
The model had to cover 20 years of allowance supply and demand, simulate over 30 interlocking policy levers simultaneously, and survive multiple revisions, shareable in both Excel and a public web tool. Climact's prior version, built in standard Excel formulas, was not robust enough to handle this. Climact decided to use River and its innovative modeling technology and build a new visual, robust and documented model in Excel.
Iterative logic, interdependencies and complex scenarios
The EU ETS works by capping total greenhouse gas emissions across power and heat generation, industry, aviation, and maritime transport. Each allowance gives the right to emit one tonne of CO₂ equivalent. The cap declines each year according to a linear reduction factor (currently 4.3% per year), and is further adjusted by scheduled rebasings, sector scope changes, and set-asides for funds like the Innovation Fund. On top of this annual cap trajectory sits the Market Stability Reserve, which absorbs or releases allowances based on the total volume in circulation, creating feedback loops that ripple through supply year after year.
Formula chains spread across a dozen sheets. Complex cell-specific formulas. Adding a scenario meant duplicating entire sheets. Auditing the model took days and still left gaps.
The full model, from raw emissions to per-member-state auction revenues, is a visual Model Map any team member can read immediately. Scenarios are configurable. The iterative logic is transparent and robust.
Four capabilities that weren't viable before
Two modelers, 15 users
Climact brought two climate policy consultants to build the new ETS1 model, to be used in total by 15 users. Neither had used River before. Because River's operations map directly to how analysts think about data, both were productive within their first week, no new programming language or database concepts required.
"River had everything I needed: a tool easy to get to grips with, agile modeling, and a model logic you can read directly."
Simon Lalieu, Senior Consultant, ClimactThe Model Map also serves as living documentation, always in sync with the model itself, no separate diagram to maintain.
A model the whole coalition can rely on
The rebuilt ETS1 calculator was delivered ahead of the Commission's Q3 2026 legislative proposal. It serves multiple audiences simultaneously: Carbon Market Watch analysts running the full Excel model, stakeholders accessing predefined scenarios via a public web tool, and Climact's team updating it as new positions emerge from the Commission, Parliament, and Council.
A high-stakes model on a robust foundation
The EU Emissions Trading System (ETS1) is one of Europe's most consequential climate policy instruments. In 2025, Climact, a Brussels-based climate consultancy, was engaged to build a calculator that lets policymakers, NGOs, and analysts test how different design choices affect the EU's ability to meet its 2030 and 2040 climate targets.
The model had to cover 20 years of allowance supply and demand, simulate over 30 interlocking policy levers simultaneously, and survive multiple revisions, shareable in both Excel and a public web tool. Climact's prior version, built in standard Excel formulas, was not robust enough to handle this. Climact decided to use River and its innovative modeling technology and build a new visual, robust and documented model in Excel.
Iterative logic, interdependencies and complex scenarios
The EU ETS works by capping total greenhouse gas emissions across power and heat generation, industry, aviation, and maritime transport. Each allowance gives the right to emit one tonne of CO₂ equivalent. The cap declines each year according to a linear reduction factor (currently 4.3% per year), and is further adjusted by scheduled rebasings, sector scope changes, and set-asides for funds like the Innovation Fund. On top of this annual cap trajectory sits the Market Stability Reserve, which absorbs or releases allowances based on the total volume in circulation, creating feedback loops that ripple through supply year after year.
Formula chains spread across a dozen sheets. Complex cell-specific formulas. Adding a scenario meant duplicating entire sheets. Auditing the model took days and still left gaps.
The full model, from raw emissions to per-member-state auction revenues, is a visual Model Map any team member can read immediately. Scenarios are configurable. The iterative logic is transparent and robust.
Four capabilities that weren't viable before
Two modelers, 15 users
Climact brought two climate policy consultants to build the new ETS1 model, to be used in total by 15 users. Neither had used River before. Because River's operations map directly to how analysts think about data, both were productive within their first week, no new programming language or database concepts required.
"River had everything I needed: a tool easy to get to grips with, agile modeling, and a model logic you can read directly."
Simon Lalieu, Senior Consultant, ClimactThe Model Map also serves as living documentation, always in sync with the model itself, no separate diagram to maintain.
A model the whole coalition can rely on
The rebuilt ETS1 calculator was delivered ahead of the Commission's Q3 2026 legislative proposal. It serves multiple audiences simultaneously: Carbon Market Watch analysts running the full Excel model, stakeholders accessing predefined scenarios via a public web tool, and Climact's team updating it as new positions emerge from the Commission, Parliament, and Council.
Get started with River
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