The most powerful onshore wind farm in the UK, which has cost £50m to build, has officially opened in mid Wales.
The mountain plateau of Cefn Croes, near Aberystwyth, is home to 39 turbines, up to 328ft (100m) high.
It has the capacity to supply 42,000 homes with electricity, which is 20% of all onshore wind power in Wales.
But Campaign for the Protection of Rural Wales (CPRW) said it spoiled the landscape and described it as "a quick energy fix".
Developers Falck Renewables said wind farms with fewer but more powerful turbines were the future for green energy.
The Italian company said the equivalent of four million tonnes of carbon dioxide emissions would be saved by the wind farm in the Cambrian Mountains during its 25-year lifetime.
It added that noise from the site and the visual impact were minimal.
The Welsh Assembly Government expects 10% of electricity generated in Wales to come from renewable sources by 2010.
Economic Development Minister Andrew Davies, who performed the opening ceremony, said: "Wind power is currently the only viable option to provide the bulk of our renewable energy needs, and with excellent wind resources in Wales, sensitively designed wind farms can play an important role in achieving these objectives".
The CPRW said the wind farm would not help to significantly reduce carbon dioxide emissions and its benefits were outweighed by turbines' visual impact.
Director Peter Ogden said: "We think Wales' landscape is being traded for a quick energy fix.
CEFN CROES FACTS
39 turbines varying in height from 294ft-328ft (89m - 100m)
58 megawatt capacity and 500m above sea level
It can supply enough power to meet needs of 42,000 homes
Estimated 4m tonnes of CO2 emissions will be saved over 25-year lifetime
There are 20 onshore wind farms in Wales and 395 turbines
"The government should be developing offshore and marine technology which is much more effective."
Roger Jones, asset manager for Falck Renewables, said power generated at Cefn Croes was nearly double the output of the largest wind farm in Wales, a 103-turbine site at nearby Llandinam, built in the early 1990s.
"We believe this is an example of the future of green energy production in Wales," said Mr Jones.
"This is the most powerful onshore wind farm in the UK and ultimately sites like Cefn Croes will have an impact on greenhouse gas emissions".
He said the wind farm could not be seen off the nearby main road and the nearest property was nearly two miles away.
There are nine wind farms and 277 turbines in mid Wales alone, which has led some to dub the region "Europe's windfarm capital".
Martin Wright, spokesman for the Cambrian Mountains Society and former chairman of a group opposing Cefn Croes, said: "Cefn Croes can been seen from the top of Plynlimon, in fact you can see about 300 turbines from there".
He said further plans included 180 400ft turbines above Tregaron and up to 150 turbines at Nant y Moch, both near Aberystwyth.
Last year, the assembly government said building more onshore wind farms was the "only viable option" to meet Wales' clean energy targets.
It identified areas in north, mid and south west Wales as places that could accommodate more windfarms.