Meridian Energy Ltd could have a decision from the Environment Court on its new Waitaki River power scheme before its Project Hayes wind farm.

Judge Jon Jackson, with commissioners, heard both Environment Court appeals on Project Hayes on the Lammermoor Range and the north bank tunnel concept power scheme on the Waitaki River between the Waitaki dam and Stonewall.

The Project Hayes hearing finished in mid-February and the Waitaki River hydro electricity scheme hearing on Tuesday.

At the conclusion of the Waitaki power scheme hearing, Judge Jackson reserved a decision, but indicated to Meridian counsel Jo Appleyard the north bank decision may come first.

Judge Jackson did not specifically refer to Project Hayes, but was replying to a comment from Ms Appleyard that she was aware he had "one or two other decisions to write, as well".

Judge Jackson replied: "Yes. You may get a decision first."

Judge Jackson did not indicate when the Waitaki scheme decision would be out, but the latest indication from the court was the Project Hayes decision might be by the end of August.

The north bank tunnel concept hearing, originally set down for up to five weeks took only 11 days, because four of the five appellants withdrew.

The Project Hayes hearing took more than 30 days.

Judge Jackson also indicated the Waitaki scheme decision might be in two parts.

He said during the hearing that if - emphasising the word "if" - the court decided to grant water from the Waitaki River for the north bank scheme, that would be followed by parties being involved in formulating the conditions which would be attached.

The north bank scheme is estimated to cost Meridian almost $1 billion.

It would take up to 260cumecs of water from an intake just west of the Waitaki dam into a 34km long tunnel with one powerhouse contributing up to 1400GWh of electricity a year.

The outfall would be at Stonewall.

Project Hayes, estimated to cost $2 billion, would have up to 176 wind turbines on the Lammermoor Range, capable of producing up to 630MW of electricity