People are stealing about 60% of the electricity generated in Liberia annually by making illegal connections to their homes and businesses, the state-owned power utility has said.
The theft caused annual losses of about $35m (£27m), Liberia Electricity Corporation officials told state radio.
This was robbing the utility of cash for extending power supply, they said.
Liberia is trying to rebuild its power sector, destroyed during a civil war which lasted from 1989 to 2003.
The US is giving financial and technical aid to the West African state to increase connectivity, as part of the Power Africa initiative launched by former US President Barack Obama to bring electricity to 50 million people in sub-Saharan Africa by 2020.
But up till now only 12% of Liberians - and less than 20% of residents in the capital, Monrovia - have electricity, one of the lowest access rates in the world.
The government has set itself the target of rolling out electricity to 70% of Monrovia's population of more than one million by 2030.