(Bloomberg) -- A halt of Russian gas supplies to the European Union could potentially reduce its gross domestic product by as much as 1.5% if the next winter is cold and the region fails to take preventive measures to save energy, according to new estimates from the bloc.

The European Commission is set to warn that, in the event of an average winter, a cut-off of gas shipments from Moscow would reduce the GDP by between 0.6% and 1%, says a draft EU document seen by Bloomberg News. The EU’s executive arm is planning a set of recommendations to member states -- including reductions to heating and cooling use and some market-based measures -- to mitigate the impact of a possible full disruption by Russia, its biggest source of imports. 

“An EU coordinated response before the winter and in solidarity between member states would limit the negative impact on GDP and jobs of a possible major disruption,” the commission said in the draft document, titled “Save gas for a safe winter.” It estimated taking early action to reduce demand in the case of an average winter could limit the negative impact of a supply cut-off on GDP to 0.4%.

The EU’s biggest challenge this winter is to ensure sufficient gas reserves to get through peak demand for heating and power. While storage levels last year were 10 percentage points lower than in the 2016-2018 period, they are currently in line with the historic average, above 63%, or equal to 46 days of winter consumption, according to the EU document, which may still change before publication set for Wednesday.

The EU remains worried that Russia will decide to shut off supplies to the bloc in retaliation for multuple rounds of sanctions. It has currently closed the Nord Stream 1 pipeline for maintenance. The pipeline was only flowing at about 40% capacity before the repairs began, and it’s not known at what volume the pipeline may resume later this week. 

Read more: EU Plans Steps to Cushion Impact of Sudden Russian Gas Halt

Simulations by the commission and gas system operators show that a cut-off of Russian imports in July would mean the EU reserves would be filled to 65-71% at the start of November, below the 80% target. That indicates a gap of 30 billion cubic meters of gas during the winter under normal weather conditions and continuously high liquified natural gas supply, implying a very high risk of storage running empty in several member states in April 2023, the draft showed.

“Assuming persistently tight international gas markets, replenishing storage in the summer of 2023 would be very challenging and that would in turn impair preparations for the following winter season,” the commission said. “Storage filling levels in October 2023 would only be 41%.”

Curtailments in Russian shipments have affected 12 member states and prompted Germany to raise its gas-risk alert to the second-highest “alarm” level last month. Overall flows from Russia in June were less than 30% of the average from 2016 to 2021, according to the document.

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