CNBC -- Russian gas accounts for some 40% of Europe's total consumption and EU gas imports from Russia have fluctuated between 200 million to 800 million euros ($880 million) a day so far this year.

The possibility a change of currency could throw that trade into disarray sent some European and British wholesale gas prices up around 15-20% on Wednesday.

The Russian ruble briefly leapt to a three-week high past 95 against the dollar before settling close to 100 after the shock announcement.