Kejriwal, who took oath Saturday, also suggested an audit into the power companies in the capital, giving them time until Wednesday morning to file their objections if any.
In the meantime, he said that those consuming up to 400 units -- 0 to 200 units and 201 to 400 units -- of electricity a month would get 50 percent subsidy.
The new power rates will go into effect from Wednesday -- Jan 1.
This would benefit some 28 of the 34 lakh households in Delhi, he added after a cabinet meeting, describing the intended beneficiaries as the poor and the middle class.
Tuesday's decision came a day after he announced that 667 litres of water would be provided free to all households in the capital who have metered connections.
Kejriwal, whose AAP made providing water and drastically cutting power rates its main election promise, also met Comptroller Auditor General (CAG) Shashi Kant Sharma to seek an audit of the power companies.
Kejriwal told the media that his government would wait for the responses from the companies before taking a final decision on audit.
"By tomorrow evening we will decide whether to go for audit or not," he said.
He estimated that the revision in electricity tariff would cost the government Rs.200 crore but Rs.140 crore of this would be borne by the power companies against their outstandings.