Energy is the main pillar of the Kremlin's budget. The Russian government got an average of 43% of its revenue from oil and natural gas between 2011 and 2020.
While the price for Russia's main export benchmark to Europe, Urals crude, has been discounted by $35 a barrel compared with international benchmark Brent, Russia's revenue losses have so far been limited because of generally higher oil prices.
The latest sanctions would likely to have a "significant impact" on Russia's ability to keep funding the war because of its dependence on the European oil market, said John Lough, associate fellow with the Russia and Eurasia program at the Royal Institute of International Affairs in London.
"Further reductions of federal tax revenues on top of an already anticipated 5-10% decline in GDP from existing sanctions will have huge consequences for government spending across the board and may generate serious social discontent," he said.
But he warned the embargo also carried risks: "A sharp rise in the oil price could mitigate the effects on the economy if Russia is able to divert crude to non-European markets."
Meanwhile, Russia will try to exploit differences among EU countries, which could be worsened by high energy prices.