It was up from 2.3 billion units in May.
"Delayed arrival of monsoon and soaring temperatures in parts of the country led to an increase in volumes traded in the spot power market at IEX in June 2014," the exchange said in a statement.
The daily average cleared volume in June rose to 87 million units, an increase of nearly 16 per cent over 76 million units traded in the previous month.
Tamil Nadu and Kerala were worst affected as they could import only an insignificant amount of power, IEX said.
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The much awaited second line of Raichur-Solapur transmission interconnection was commissioned on June 30.
Following that, IEX said it hopes to serve stakeholders better once the system operator -- National Load Despatch Centre (NLDC) -- starts firm scheduling on the interconnection and allocate capacity to the exchanges.
Increase in demand coupled with transmission constraints led to the firming up of prices on the exchange.