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Sigalda Power Station Expansion

Welcome to the Sigalda expansion website. Here you will find key information about the project and the associated construction works.

Sigalda Expansion Project

The expansion involves extending the existing powerhouse to the south-west, installing a fourth generating unit and adding a new penstock. The tailrace channel will also be widened near the station. This will increase the station’s installed capacity from 150 MW to up to 215 MW.

The aim is to make the electricity system more flexible and better able to meet peak demand and respond to changes in electricity consumption and generation. The new equipment will also improve efficiency. The expansion will use the existing storage reservoir and will not require any new reservoirs.

Landsvirkjun has awarded contracts to Ístak for earthworks and construction of the main structures, and to DSD Noell for intake racks, water-intake gates and the penstock. Efla will supervise the construction works.

Completion is planned for autumn 2029.

Foresight in the original design

When Sigalda Hydropower Station was designed and built in the 1970s, provision was already made for a future increase in generating capacity. Although three generating units were installed, the design allowed for a fourth.

A concrete passage for an additional penstock was built beneath the intake dam, and the powerhouse was designed to accommodate an extension to the south-west. Nearly half a century after the station began operating, this foresight is now making its expansion easier.

  • Installed capacity

    0MW

    increase from 150 to 215 MW

  • Rated discharge

    0m3/s

    increase from 240 to 350 m3/s

Construction progress

Preparatory works began in March 2025. These included preparing the site for workers’ accommodation, securing a water supply and installing electricity, lighting and telecommunications. Excavation for the powerhouse extension began in autumn 2025.

The works are planned to allow the station to remain operational throughout much of the construction period. Electricity generation will need to stop temporarily for work on the intake and tailrace channel. A shutdown lasting approximately four months is planned for 2028, although the exact timing has yet to be confirmed.

The number of people working on the project will vary according to the construction activities and progress. The accommodation was planned to house up to 140 people working for Landsvirkjun and its contractors.

Construction in summer 2026

During the summer of 2026, Ístak worked on establishing workers’ accommodation and site facilities for the Sigalda expansion. Preparations for the next stages of construction were carried out in parallel.

Work on these facilities continued in September, alongside earthworks and rock reinforcement at the construction site. The rock reinforcement helps ensure safe working conditions as construction progresses.

How will the area change?

Here you can see how the power station area will look before and after construction. Drag the slider left and right to see the change.

BeforeAfter
BeforeAfter

Q&A

  • The expansion involves installing a fourth generating unit, comprising a water turbine and a generator, at Sigalda Hydropower Station. The powerhouse will be extended to the south-west, a new penstock will carry water to the turbine, and the tailrace channel will be widened near the station. This will increase the station’s installed capacity from 150 MW to up to 215 MW.

    The original design anticipated a fourth generating unit. A concrete passage for an additional penstock was built beneath the intake dam, and the powerhouse was designed to accommodate an extension. These provisions now make the expansion easier.

  • The expansion will increase generating capacity and improve the flexibility of Iceland’s electricity system. With a fourth generating unit, Sigalda will be able to generate more electricity at times of high demand and respond more effectively to changes in electricity consumption and generation.

    The new equipment will also improve efficiency. The expansion will use the existing reservoir, with no new reservoirs required.

  • Installed capacity will increase by up to 65 MW, from 150 MW to up to 215 MW. The maximum flow through the turbines will rise from around 240 m³/s to approximately 350 m³/s, depending on the final equipment design.

    This will allow the station to use more water at any one time when additional power is needed.

  • The main purpose of the expansion is to enable Sigalda Power Station to generate more electricity when demand is high. The increase in installed capacity does not mean that annual generation will rise by the same proportion.

    The new equipment will improve efficiency, but annual generation will depend on water availability and how the station is operated within the wider electricity system. The expansion will use the existing reservoir, with no new reservoirs required.

  • According to the environmental impact assessment, water levels and fluctuations in Krókslón reservoir during operation are expected to remain similar to those under current operating conditions. However, flow through the station and water speeds in its waterways may temporarily increase when it operates at higher output.

    During construction, the water level in Krókslón will need to be lowered to allow work on the intake and tailrace channel. During this period, water will be diverted around the station through Sigöldugljúfur canyon.

  • Preparatory works began in 2025, and completion is planned for autumn 2029.

    The station will remain operational during much of the construction, but electricity generation will need to stop temporarily for work on the intake and tailrace channel. A shutdown lasting approximately four months is planned for 2028, although the exact timing has yet to be confirmed. During the shutdown, water will be diverted around the station.

  • The Icelandic National Planning Agency issued its opinion on the environmental impact assessment for the Sigalda expansion in December 2023. The detailed local plan for the expansion came into force in April 2024, and a power generation licence was granted in September that year.

    A development permit granted in February 2025 was subsequently annulled, partly because of shortcomings in the assessment of the project’s effects on water bodies. Landsvirkjun therefore submitted an addendum to the environmental impact assessment report. The Housing, Infrastructure and Planning Agency (HMS) issued its opinion on the addendum in July 2026, concluding that effects on water bodies and aquatic life were likely to be negligible.

    The supplementary environmental assessment was completed in July 2026 with the publication of HMS’s opinion. The remaining permit required for the planned works is a development permit for work on the station’s tailrace channel. The application is currently being processed.

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About Sigalda Power Station

Sigalda Power Station was commissioned in 1978. It is a 150 MW hydropower plant with an annual generation capacity of 930 GWh. The station utilizes Krókslón reservoir as its intake and operates with a total head of approximately 72 metres. Discharge flows through a channel into Hrauneyjalón reservoir. The powerhouse houses three 50 MW generating units.

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