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Project Neptune
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At a glance
Pumped Storage

Hydro Type


Project Type

450 MW


1,074,560 MWh

Energy Production per Cycle

Operational Term

Tariff (year 1)

GBPm 64.7

EBITDA (year 1)

GBP 853.6

Total Investment

  • Clean Storage is a greenfield hydro pumped storage project located in the Nantlle Valley area in North Wales, utilising existing infrastructure.

  • The sites will have a combined power capacity of 450 MW and expected electricity  generation of 2,944 MWh per cycle.

    • One cycle is 13.0 hours to fill and 6.5 hour to empty the storage

    • Technically there is more than one cycle per day possible, but realistically there is one cycle a day executed on average

  • The feasibly, early stage development and acquiring the land rights stage are completed.  Approximately 5 years of development and 5 years of construction is required such that  the plant is expected to be operational as of 2033.

  • The operational term for the plant is indefinite. The combined rate of capacity, wholesale  and balancing mechanism revenue equals 205.7 GBP / kW.

  • Once operational, the plant is expected to generate annual revenue of GBP 118.4 million and an EBITDA of GBP 103.0 million.

  • A total investment of GPB 550-600m is required in development cost and capex.


Share of equity


Share of debt


INDICATIVE IRR 6-year holding period


Project IRR


Equity IRR

*Based on a high level assessment while varying the debt leverage between 70% and 80%

Why does it matter?

  1. Availability of electricity is becoming he key factor, This project allows to align supply and demand of green energy.

  2. The Parliament is working on new regulation to favor these kind of green batteries more as these are crucial for the growth of clean energy and its availability.

  3. Wind and solar have the challenge that tey are available when nature says so. Demand for electricity does not follow the same pattern. Wind and Solar are therefore dependent on a green storage for their electricity.

Hi tech storage of green energy in batteries and other modern storage technologies very often involves rare earth metals and other challenges to nature. 

Is it supported by the community?

  1. English regulation is changing to even support these kind of projects more actively

  2. The project is located in an area where there are many wind farms in development. There is little economic activity in this area and the local communities largely support this project

  3. The project is supporting the local community and it is supporting local environmental initiatives to protect the landscape and integrate the facility to the local ecosystem.

Is this proven technology? 

  1. We know what we are doing as we are using only long term tested and proven hard ware. These pump storage projects have been successful in the alps and in Switzerland for many decades. 

  2. In the UK we see 5 new such projects being implemented as the old one have proven very reliable and profitable. 

  3. Hydro power has been around for 200 years. The technology we are using is only more modern but follows the same principle. 

  4. The new part in this project is not the technology. It always have been there and it always have been reliable. The new part on this project is that we use it for clean energy and focus on the storage of electricity from Wind and Solar

Where is the project actually located?

  1. The project is in north Wales

  2. It is next to Windfarms well next to the most windy parts in Wales, on the west coast. 

  3. The Project is close to the consuming industry for green power in the Manchester and Birmingham area

  4. The location in for the project is Ober Altstadt 10, 6300 Zug, Switzerland

Who is the person I can talk to about this project:

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