Portrait of Guillaume Castroviejo

Guillaume Castroviejo Consultant

Guillaume is a member of Oxera’s Regulation and Market Design team. He specialises in the economic regulation of infrastructure and utilities.

Before joining Oxera, he obtained a Master’s degree in Economics of Markets & Organizations at Toulouse School of Economics, and a double Bachelor’s degree in Economics and Mathematics and Computer Science.

He advises regulated companies in the water, energy, and aviation sectors in their interactions with the regulator, including supporting them in assessing their cost efficiency through various quantitative benchmarking methods. He regularly provides strategic advice to investors or regulated operators.

Guillaume also has significant experience in due diligence exercises and merger procedures involving regulated entities.

Guillaume speaks English, and French.

Tel: +33 (0) 1 80 20 91 84

Guillaume's specialisms include:

Selected
professional experience

  • Impact assessment of a merger between several electricty distribution network operators (2024–)

  • Economic study of the interdependence between aeronautical and commercial activities on behalf of a European airport (2024–)

  • Development of a series of recommendations as part of Oxera’s response to Ofwat’s public consultation on its approach to assessing mergers (2024–25)

  • Provided advice to a water company in formulating its response to cost assessment in Ofwat’s PR24 draft determinations—contributing towards achievement of a substantially better outcome at final determination stage (2024)

  • Due diligence advice in relation to the recapitalisation of Thames Water, the largest water and sewerage company in England and Wales (2024)

  • Independent review of the effectiveness and incentives of the legislative and regulatory frameworks applicable to large French airports, including providing regulatory and strategic advice to a key stakeholder (2023–24)

Qualifications

  • MSc Economics of Markets & Organizations, Toulouse School of Economics, France

  • BSc Economics, Toulouse School of Economics, France

  • BSc Mathematics and Computer Science, University Toulouse 1 Capitole, France

Latest Insights:  Guillaume Castroviejo

Agenda
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Depiction of Ofgem RIIO-3 Draft Determinations

Ofgem RIIO-3 Draft Determinations

On 1 July 2025, Ofgem published its Draft Determinations (DDs) for the RIIO-3 price control for the GB electricity transmission (ET), gas distribution (GD) and gas transmission (GT) sectors for…
Agenda
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Depiction of Water mergers: Ofwat’s updated approach

Water mergers: Ofwat’s updated approach

Across industries, mergers and acquisitions play a key role in shaping business landscapes, enabling companies to evolve, grow and innovate. However, they must first undergo assessment by relevant competition and…
Agenda
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Depiction of RIIO-ED2 Final Determinations

RIIO-ED2 Final Determinations

On 30 November 2022, Ofgem published its Final Determinations (FDs) for the RIIO-ED2 price control covering the electricity distribution (ED) sector for the next five years from April 2023 to…
Agenda
8 minute read
Depiction of Like an economist at Wimbledon

Like an economist at Wimbledon

To what extent is future success affected by past success? This topical question has implications for many areas of society, including education. However, a new study suggests that the answer…
Events

Network on the Green

Join us for an exclusive summer evening at Swingers Crazy Golf, curated for legal professionals below Partner or KC level. Whether you’re a pro mini-golfer or a first timer, it’s a perfect opportunity to step away from the office for an evening of competition and fun. There’ll be delicious street… Read More

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