Activists from the "We Want Accountability" campaign linked arms outside the building in Beirut's Corniche al-Nahr district, preventing employees from entering.
A scuffle broke out when security forces tried to pull protesters away from the entrances, resulting in several windows being broken.
Demonstrators lifted a massive banner outside the ministry that read "One bill, not two!" in reference to payments for government-provided electricity, as well as to local generator companies.
Lebanon is plagued with frequent power cuts because of outdated and damaged infrastructure.
Local generator companies have filled the gap by providing power when state electricity cuts off -- but they often charge exorbitant prices.
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The poor condition of the state's power infrastructure has been a major source of public frustration, and featured prominently in recent protests that saw thousands gather in central Beirut.
The "We Want Accountability" campaign has played a major role in those demonstrations, which were sparked by a rubbish collection crisis but later broadened to protest against electricity and water shortages and rampant corruption.
"This ministry does what other ministries do: steal the Lebanese public's money for the past thirty years," one protester said on Tuesday.
Activists pledged additional demonstrations at other ministries and called for a sit-in on Saturday outside the government's electricity centre in Beirut.
"It's not just the ministry of energy that our movement will target, but every single ministry. We will hold every corrupt person accountable," one protester said.
"We will surprise the authorities at a new centre of corruption every time, and we will continue to demand accountability for corrupt officials," said another.