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Norway-South facing 15% risk of power rationing in the event of interconnector disconnections

Eylert Ellefsen
Archived blog post. This blog post has been transferred from our previous blogging platform. Links and images may not work as intended.


The reservoir levels in Southern Norway are very low as we know. Politicians in Norway meanwhile, against the backdrop of exceptionally high power prices, are discussing the possibility of cutting all foreign power interconnectors to secure the power supply and avoid rationing.

Energy Quantified’s blog post from August 17th - about a possible supply squeeze towards next spring - concluded that the hydropower production needs to be reduced to about 85% of normal by the new year for reservoir filling levels to reach 60% - the level required to avoid any risk of rationing next spring.

Following on from that, this blog post will present a simulation based on cutting the foreign interconnectors towards Sweden, Denmark, the Netherlands, Germany, and Great Britain, to see how the reservoir filling and production level would develop. This is a scenario simulation based on inflows and consumption from the historical weather years 2001 – 2021.


The simulations show that there is a probability of around 15% that electricity could be rationed in Southern Norway for this coming spring if all foreign interconnectors were to be switched off from early September. The simulations are based on an approximate 6% reduction in consumption due to high spot prices and the inflow scenarios are based on the weather years 2001-2021.

Inflow scenarios 2001 – 2021

The inflow scenarios are based on the Swedish Meteorological and Hydrological Institute’s (SMHI) GWh-inflow concept. The first 15 days are based on the EC-Ensemble Mean simulation from midweek 35. From day 16 onwards, we simulate the inflows based on the historical weather years 2001-2021. We have a quality check comparing the simulated inflows for the Q2-23 period with actual statistics, and the simulation quality is very good.

The scenarios are shown as simulated average, high and low percentiles - compared to long-term normals in the charts below. According to these figures, we see that normal inflow levels cannot be reached before mid-October in this scenario.

Production scenarios 2001-2021

The power balance for Southern Norway assumes no external power interconnectors but does include 600 MW of fixed imports from NO3. Normal wind and Combined Heat & Power (CHP) production are assumed, as well as a 6% reduction in consumption due to high spot prices. The hydropower will then cover the required production in this non-external interconnector calculation. The graph below outlines the different scenarios.

Based on these conditions we have calculated this virtual power balance until week 30 2023 (the end of July). We call it virtual because we haven’t checked the reservoir curves yet.

The numbers show us that hydropower production will be significantly reduced if there is no possibility of foreign exchange, which we believe would actually help the supply situation.  The average production in this scenario reaches only 83% of the long-term normal.  The numbers show us furthermore that in a normal case, the net export will be about 7 TWh, no matter how many interconnectors are online.

The chart below details the weekly numbers. Note that the simulated average for Q1-23 is close to the average level we saw during Q1-22.

Reservoir scenarios 2001 – 2021

We have so far ignored the reservoir levels in this virtual simulation. The chart below shows the 21 scenarios from week 36 2022 until week 30 2023 (end of July). Evidently, several scenarios come out very low. In the “real world”, South Norway will require imports to avoid rationing at levels lower than about 5000 GWh (8% of max cap) we assume. It depends on how the reservoir filling is distributed geographically and the grid capacity in the different regions of South Norway.

The chart which shows percentage filling rates from week 1-2022, shows that the fifth percentile comes out at zero filling as early as week 12, and stays that way until week 19. Testing more percentiles shows us that if reservoir filling reaches about 7% before rationing occurs, there is a roughly 15% risk of rationing occurring by next spring should all foreign interconnectors from South Norway be shut down.

We believe that a 15% risk of rationing next spring is not a problem by mid-September. It still seems unrealistic that imports from Norway’s interconnected neighbors will not be available during the coming winter, but such a scenario can however not be ignored as the energy situation across Europe is severely threatened.

In a worst-case scenario, it seems like South Norway will require a net import of around 5-7 TWh until the end of April, which would most likely mean a production level lower than 80% of normal in such a dry and cold scenario.

Final words

EQ has created this scenario study of the reservoir filling and risk of rationing in the case that all foreign interconnectors to South Norway are taken offline. Inflow modeling is based on the SMHI HYPE GWh concept, and the power balance data is based on the database at Energy Quantified AS.

Please contact us at if you have questions about this blog post or other requests concerning our analysis platform at

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