Interested parties now have until 1pm (local time) on 27 July to present offers for the 20-year contracts, the National Energy Commission said. The deadline was originally scheduled for April.
It will be the largest held since Chile introduced tenders to secure power purchase agreements (PPAs) for regulated clients a decade ago.
Contracts for 13.75TWh will be on offer annually, equivalent to a third of demand from the country's regulated clients.
In order to give them sufficient time to permit and build new capacity, winners of the contracts do not have to begin supplying electricity until 2021.
As with two previous tenders, this year's process includes special rules to encourage the participation of alternative renewable energy such as daytime-only blocks for Chile's growing solar power sector.
Generators will also be able to take advantage of new transmission lines bolstering capacity between northern Chile and the centres of consumption around the capital Santiago, which are due for completion in 2018.
Wind projects dominated the previous tender, held in October last year, winning more three quarters of the 1.2TWh annually on offer.
Increased competition between conventional and renewable generators and lower fuel prices have seen dramatic falls in the electricity prices secured in recent contracts.
Last October's tender secured an average price of US$79.30/MWh, down 40% from just two years earlier.