European Commission President Ursula von der Leyen described a complete cut-off of Russian gas as a "likely scenario."
"Russia is blackmailing us," she said. "Russia is using energy as a weapon. And therefore, in any event, whether it's a partial, major cut-off of Russian gas or a total cut-off of Russian gas, Europe needs to be ready."
Disagreements over energy have been building between Moscow and Brussels since the war in Ukraine began in February.
So far, 12 EU member states have been hit by a cut in gas supply from Russia. The Baltic states have chosen to stop importing Russian gas altogether.
Not all countries are on board with the plan to reduce energy usage.
Poland has already been bolstering gas reserves in preparation for a difficult winter, with storage in the country at 98 percent of capacity.
Across the EU, storage is at 64 percent of capacity. The EU is aiming to hit 80 percent by November 1.
Countries with warmer climates, like Spain and Portugal, have also been reluctant, as they would be less affected by supply disruptions.
EU leaders are urging solidarity, insisting that an economic crisis would hit all countries in the bloc triggered by a halt in gas supplies.
They say taking steps now will mitigate the impact of any future cut-off.
Individuals urged to help
It will be down to individual governments to determine where to make the cuts, but EU officials assured households that they would be protected.
Although industry and the public sector are likely to account for most of the reduction, Frans Timmerman, EU Commissioner for Climate Action Policy, urged individuals to do their bit in cutting consumption.
The EU has been working to diversify its gas supply, signing agreements with Norway, Algeria, Egypt, Azerbaijan, and the Gulf States.
That process, however, will take time to implement.
In the meantime, Russia has been threatening to cut supplies further.
State-owned energy company Gazprom warned customers this week that it cannot guarantee gas supplies.
The warning comes as Gazprom carries out maintenance on its Nord Stream 1 pipeline, which runs from Russia to Germany, but gas flows were already falling before that began.
Moscow says it does not use energy as a tool of political pressure.