Nuclear Energy’s Role in Baseload Decarbonisation

Master the Moment and Reach Your Peak with Defoes

“Defoes looks beyond simple ‘more renewables’ narratives — showing how nuclear’s high‑capacity‑factor, firm output quietly anchors Europe’s net‑zero maths, cutting the storage, overbuild and grid spend needed to decarbonise real‑world baseload demand.”

The core decarbonisation challenge is not just adding low‑carbon kilowatt‑hours, but replacing fossil baseload without losing system stability. Nuclear sits at the centre of that problem. In Europe, nuclear currently generates around a quarter of all electricity and roughly half of the continent’s low‑carbon power, making it the single largest firm, low‑carbon source in the system. Analyses from engineering academies and system‑modelling studies describe nuclear as a “low‑carbon, firm, widely available” resource that complements wind and solar by providing dependable output when variable renewables are scarce. From a Defoes standpoint, the bullish stance is straightforward: in credible net‑zero pathways, nuclear is not a marginal add‑on but a structural pillar of decarbonised baseload.

Why baseload still matters in a renewables‑heavy system

Deep‑decarbonisation studies increasingly distinguish between variable low‑carbon resources (wind, solar) and firm low‑carbon resources (nuclear, hydro with storage, gas with CCS, geothermal). A widely cited modelling study on power‑system decarbonisation shows that portfolios with firm low‑carbon capacity can achieve deep emissions cuts at significantly lower total system cost than portfolios relying mainly on variable renewables, storage and transmission. The reason is simple: firm resources cover demand during multi‑day or seasonal periods of low wind and sun without requiring enormous overbuild plus storage. Nuclear’s high capacity factors — often above 80% in well‑run fleets — make it particularly effective for this role.

Recent system‑modelling work focused on Europe finds that lowering nuclear’s overnight capital costs leads to a roughly 59% increase in optimal nuclear capacity, with corresponding reductions in storage requirements, transmission build‑out and renewable curtailment. In other words, nuclear is not just another supply option; it changes the shape of the decarbonisation problem by reducing the amount of backup and grid reinforcement needed to keep the lights on in a very low‑carbon system. For investors, this is critical: technologies that reduce system‑level costs, not just project‑level LCOE, are likely to command durable policy support.

Nuclear’s current baseload footprint

Despite closures and political contention, nuclear remains a major baseload provider in Europe. Eurostat‑based assessments show that in 2019 nuclear accounted for about 26% of EU electricity, easing only slightly to roughly 23–24% by 2024 as some reactors retired. Nuclear still provides around one quarter of Europe’s electricity and about half of its low‑carbon output, with 14 of 27 EU member states operating reactors. France alone, with 56 reactors, supplies nearly two‑thirds of its own electricity from nuclear and more than half of the EU’s total nuclear generation. Other countries, including Slovakia, Hungary, Finland and Belgium, rely on nuclear for more than a quarter of their power.

Global organisations echo this baseload story. A technical overview for Europe’s net‑zero ambitions notes that replacing nuclear’s stable baseload with purely intermittent renewables would require large amounts of storage, backup generation and grid expansion, raising both costs and system complexity. The International Atomic Energy Agency argues that nuclear can play a “critical role” not only in decarbonising electricity, but in providing heat, hydrogen and other services for hard‑to‑abate sectors, further leveraging its baseload characteristics. The International Energy Agency’s Net Zero scenarios, as reported by industry summaries, imply that global nuclear output needs to roughly double by 2050 for a cost‑effective path to net zero, even under aggressive renewables growth.

Decarbonising baseload, not just peak demand

Baseload decarbonisation is fundamentally about reshaping the residual demand profile that remains after wind and solar. System‑modelling work on firm low‑carbon resources shows that portfolios including nuclear substantially reduce the need for very long‑duration storage and extreme overbuild of renewables needed to cover rare, high‑demand/low‑renewables periods. Nuclear’s long operating lifetimes — typically 60 years or more for modern designs and life‑extended reactors — allow those system‑wide benefits to accrue over decades, smoothing the financing profile and supporting infrastructure‑grade investment cases. In the EU, this is reflected in growing emphasis on long‑term operation (LTO) of existing reactors and on new Generation III and SMR projects designed to operate as firm, low‑carbon capacity in parallel with rapidly expanding wind and solar fleets.

At the same time, nuclear’s role is evolving beyond “flat‑line baseload”. Operators in France, Finland and elsewhere are already running reactors in load‑following mode, adjusting output daily to accommodate renewables while still providing a stable floor of low‑carbon generation. Forward‑looking analyses suggest that as grids decarbonise further, nuclear will increasingly act as flexible baseload: operating most of the time, but with enough ramping capability to complement variable renewables rather than conflict with them. For investors, this evolution expands nuclear’s value proposition from a pure energy play to a broader system‑service asset.

The bullish but conditional case

The bear case is well established: high upfront capital costs, construction‑risk, waste management, and political opposition. In parts of Europe, nuclear’s share of generation is declining as ageing reactors retire and replacement projects lag, and some countries remain firmly opposed. These realities mean nuclear is unlikely to be a universal solution or an easy one.

Yet the structural decarbonisation maths are hard to ignore. Nuclear remains the largest source of low‑carbon electricity in Europe and the United States, and the second‑largest source worldwide, and modelling work consistently shows that firm low‑carbon resources — with nuclear at the forefront — materially lower the cost and complexity of deep decarbonisation. From a Defoes perspective, the bullish stance is conditional but clear: in jurisdictions that can align policy, financing and public support, nuclear is poised to remain — and in some cases regain — its role as a cornerstone of decarbonised baseload, anchoring systems where wind, solar and storage do most of the visible growth but rely on nuclear’s quiet, steady output when it matters most.