"We're already there … savings this month have already surpassed the 15% target," said senior energy strategist from Goldman Sachs, Samantha Dart. Kenzo Tribouillard | Afp | Getty ImagesShe added that northwestern Europe's estimated August gas consumption was 13% below average. "We believe this is more than enough savings to go through winter without blackouts or a heating crisis," Dart said, assuming that the average winter weather scenario holds. "Achieving the 15% reduction target vs business as usual will be difficult, but not impossible," Gloystein told CNBC. A cold winter could make it difficult to achieve the demand reduction needed in Europe.

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