The auditors will review power purchase cost, revenue billed, revenue collected, overhead and maintenance expenses, non tariff income, finance costs, reconciliation of pension trust charges, and subsidy for 2016-17, DERC said in a statement.
"The assignment will be for regulatory audit of books of account of the distribution licensees (BRPL, BYPL, TPDDL and NDMC) for True Up (reconciliation of accounts) of the financial year 2016-17," it said.
The information gathered through the audit will be used for 'True Up' of 2016-17 while finalising the tariff order for 2018-19.
BRPL that supplies electricity to south and west Delhi has 2.34 million registered consumers. BYPL has 1.58 million consumers in central and east Delhi.
TPDDL supplies power to around 1.5 million consumers in north and north west Delhi.
The discoms are 51:49 per cent joint venture between the private companies and the Delhi government.