Ukraine now needs power generators as much as military gear, President Volodymyr Zelenskyy told European leaders on Tuesday.
Mr Zelenskyy was promised more than €1 billion ($1.06 billion) in aid by a donor conference in Paris as the long Ukrainian winter draws breath.
It came as Britain announced it was imposing new sanctions on Russia for its attacks on Ukraine’s energy grid.
The damage done by Russian missiles is aimed at making Ukraine “the darkest place in Europe”, Mr Zelenskyy said.
“That is why generators and uninterruptible power sources have now become as necessary in Ukraine as armoured vehicles and bulletproof vests."
UN Secretary General Antonio Guterres said the 10-month war was a "relentless humanitarian nightmare".
Russia acknowledges shelling Ukraine’s energy network in strikes that Mr Zelenskyy said had left 12 million people without power.
Instead of his usual appeals for tanks and missiles, he urged allies to buy energy-efficient LEDs to help limited power supplies go further.
European Commission President Ursula von der Leyen said the EU would meet this request with €30 million ($31.6 million) to buy LEDs.
She said the EU was looking into Mr Zelenskyy’s call to allow more enable more electricity exports between Ukraine, Moldova and EU members.
“In these times of literal suffering and darkness, it is so important to bring light to Ukraine,” she said.
French President Emmanuel Macron, hosting the Paris summit, urged support from a broad alliance of donors as he echoed Mr Zelenskyy's call for humanitarian aid to be co-ordinated like military aid.
“You don’t need to be a western country to be convinced of the need to support Ukraine over the long term,” Mr Macron said.
He announced a new online mechanism under which people in Ukraine can request emergency aid such as clothing, food and water from donors.
Addressing the conference by video link Mr, Guterres said the scale of the destruction called for more than immediate humanitarian aid.
"We must invest in recovery and reconstruction to prevent the crisis from cascading into poverty, hunger and destitution for millions of Ukrainians," he said.
Germany meanwhile announced €50 million of new funding to help Ukraine through winter.
Foreign Minister Annalena Baerbock said heart operations were taking place by the light of smartphones because of power cuts in Ukraine.
It comes despite donations of generators by Ukraine’s allies to keep hospitals running during the strikes.
Ukraine conflict - in pictures
Russian President Vladimir Putin “wants to break Ukrainians with his tactic of freezing them to death. We will not allow that,” Ms Baerbock said.
As well as LEDs, Mr Zelenskyy said Ukraine needed transformers and gas supplies and called for international observers to monitor power plants.
He warned European leaders of a possible fresh wave of migration if they do not address the winter crisis.
Mr Zelenskyy added: “We do not yet have such a modern air defence system that can shoot down Russian missiles and drones 100 per cent.
“However, we can create such a decision-making system that can 100 per cent make Russia's terrorist tactics meaningless.”
EU border agency Frontex said on Tuesday that 225,200 Ukrainians entered the bloc in the past week, a number that has held broadly steady for weeks.
Britain separately announced it was imposing sanctions on 12 Russian military officers over what it called “evil attacks” on civilians.
The commanders of Russia’s airborne and strategic missile forces were among those hit with asset freezes and travel bans.
Another four people and entities were sanctioned in Iran for alleged involvement in supplying drones to Russia.
“Russian forces’ calculated attacks on cities and innocent civilians in Ukraine will not go unanswered,” UK Foreign Secretary James Cleverly said.