ESI Super and SPEC Super have agreed to merge and create a $3.4 billion fund.

The merger was flagged in April this year and is expected to be completed by March next year.

The decision follows Corrs Chambers Westgarth, Minter Ellison and KPMG completing a legal and tax due diligence process on both funds.

The merged fund will adopt SPEC Super's administration model while ESI Super's funds management and financial services team will be used to manage assets.

In a joint statement, the funds said the merger would provide a number of benefits including more funds under management, which would present more investment opportunities at a lower cost and cost savings of around $2 million a year.

These cost savings will come from sharing services and economies of scale.

"On the surface, ESI Super and SPEC Super share many common attributes … while we both maintain a focus on employees in the energy industry, we are also public offer funds which can accept membership from the general public," said Bob Henricks, chair of ESI Super and SPEC Super.