Europe's appetite for Russian gas shows no sign of abating three days after Russia invaded Ukraine.

On Sunday morning, Gazprom said gas exports from Russia to Europe via Ukraine were going as planned.

European imports of Russian gas through Ukraine jumped by nearly 40% on Thursday, the day the invasion began, according to figures from the grid operator.

Western sanctions on Russia have not affected oil and gas.

Europe has continued buying Russian gas.

The continent came to depend on it

Europe used to have reliable gas supplies from the North Sea field. Russia has the largest reserves of natural gas.

The European Union relies on Russia for 40% of its gas, more than twice as much as Norway.

William Jackson, an economist at Capital Economics, estimated that Russia sold about $100 billion worth of oil and gas to Europe in 2011. According to the report, about a third of Europe's gas in 2020 was supplied by Gazprom.

Germany came to depend on it

Russia is the largest supplier of gas to Germany. Germany has been trying to build a new gas line to bring in more gas from Russia, as it has been phasing out nuclear power. This is the second part of the Nord Stream 2 project, which will follow a similar route through the Baltic Sea.

The project was suspended by Germany after Russia invaded.

The cost is comparatively low

Market forces pushed up the price of non-Russian gas, which led to increased European imports of Russian gas on the day of the invasion.

A gas analyst said on Thursday that non-Russian gas prices were well above the likely sales price for many Gazprom import contracts.

Russia is assumed to be a reliable commercial partner for the gas industry by the former chair of the Department of Energy Systems at the Institute for Energy Technology at Berlin University of Technology.

Lawmakers have eyes on consumer energy costs

Home energy bills have gone up due to soaring gas prices. European lawmakers are wary of scaring their voters with the possibility of more price increases.

Ursula von der Leyen, president of the European Commission, said that the EU would be able to cope with any disruption in gas imports.

Europe has been slow to shift to renewables

The EU has committed to using renewable energy but the buildout isn't happening fast enough to ease its reliance on Russian energy

Natural gas is 25% of the bloc's energy. Solid fossil fuels such as coal and renewable energy and biofuels make up the rest.

Tim Schittekatte, a research scientist at the MIT Energy Initiative, told CNBC that there is not enough grid capacity to take up more renewable energy in Europe.

Russian gas helps grow European crops

Europe uses gas to make key ingredients. Disruption to gas supplies can affect the ability to grow crops and feed the population.