The first day of the final session of a public inquiry into plans for five wind farms and an overhead electric line was held in Welshpool yesterday, with members of The Alliance campaign group warning against the "sheer scale" of planned development.
Government targets for onshore wind have also already been met, Dr John Constable, of the Renewable Energy Foundation, told the hearing at the Royal Oak Hotel.
Dr Constable said: "Onshore wind is already at or above a reasonable level. There is no further need for further consents for on-shore wind."
Peter Minto, from Natural Resources Wales backed Dr Constable's claims, saying: "There is not a great need to pepper pot Wales with these developments."
The Alliance attempted to submit a new document to the inquiry, which spokesman Brett Kibble said showed the full impact of both existing and planned wind farms in Mid Wales, but planning inspector Andrew Poulter told them it was too late.
Mr Kibble said: "We did not feel there was anything you could pick up to see the sheer scale of how further development would affect Mid Wales, so we developed a tool which would allow the secretary of state to see where there is already development and where planned developments are.
"It is important that the secretary of state sees the impact everything would have on Mid Wales."
But Mr Poulter said if he accepted the new document, he would have to allow all other parties the chance to look into it and prepare responses, so refused to accept it as further evidence.
He added: "I have to ask myself if I have enough information on cumulative impact in front of me and the answer is - yes I do."
The inquiry, which started last June and is expected to formally close on May 30, is into proposed wind farms in Llanbadarn Fynydd, near Llandrindod Wells; Llaithddu, near Newtown; Llandinam, near Llanidloes; Llanbrynmair, near Machynlleth; Carnedd Wen, near Machynlleth; with a 132kV overhead electric line connection from a Llandinam wind farm to the Welshpool substation.
The plans are being fought by The Alliance group, which is made up of 21 organisations together with Powys County Council.
If the plans are given the go ahead by Mr Poulter, it is expected to pave the way for the National Grid's Mid Wales Connection Project, which would see a 33-mile power line built to carry energy from generated by proposed Mid Wales windfarms from Cefn Coch, near Llanfair Caereinion, to a national network substation at Lower Frankton, near Oswestry.
Next week the developers and The Alliance will all give closing statements, before Mr Poulter retires to consider his verdict, which will be given later this year.