The last working reactor, ordered closed by the EU because it is considered too similar to the one that exploded at Chernobyl in 1986, boasts a capacity of 1,320 megawatts, making it one of the largest nuclear reactors in the world.
Lithuania, one of the two most nuclear-energy dependent nations along with France, had been hoping that the EU would allow it to keep the plant open for another two to three years, but Brussels, which demanded the reactor's shutdown as part of Lithuania's membership agreement, flatly refused.
The Ignalina plant supplied over 70 per cent of Lithuania's electricity needs, only France receives more of its kilowatt needs from nuclear power.
The Baltic nation of 3.4 million people will cover the shortfall by buying power on the open market from Estonia, Belarus, Ukraine and Russia.
By 2013, Lithuania hopes to build a new natural-gas power plant, but that would not be enough to meet its own energy needs.
Many Lithuanians are worried that they will become dependent on Russian gas supplies, which they fear may stop without warning given Russia's snap decisions in the past to shut off supplies to Ukraine.
However, Andrius Kubilius, the prime minister, does not share the view.
"Lithuania could have done its homework better preparing for the closure, but it won't be left without energy next year. I believe our country, together with its Baltic neighbours, will have an energy market similar to the Nordic countries and other EU regions," he told Lithuanian Radio.