Community Windpower said the 22 turbines would produce electricity more than 40 per cent of the time, powering the equivalent of nearly 60,000 homes.
The firm based its claims on new turbine technology and “exceptionally high” average wind speeds at the site, seven miles south east of Dunbar.
By contrast, Scotland’s onshore wind farms have operated for an average of about 22 per cent of the time in recent years, despite being expected to average some 30 per cent.
Community Windpower claimed productivity levels would be comparable to some gas-fired power stations – but that was challenged by other groups.
The new 80 megawatt (MW) development, called Wester Dod community wind farm, would comprise an extension to the existing 16-turbine Aikengall site, which opened three years ago.
The firm said no Scottish wind farm with more than 10MW capacity had achieved a long-term productivity rate, or load factor, of more than 40 per cent.
It said Aikengall, which has a 48MW capacity, had achieved 37 per cent productivity this year.
Community Windpower said the project would produce an average of £250,000 a year for community projects over its expected 25-year lifespan.
Five permanent maintenance jobs would be created, along with some 100 temporary construction posts.
The firm expects ministers to announce the fate of the plans shortly following an inquiry.
Senior project manager Gillian Cropper said: “Aikengall is one of the best-performing wind farms in Scotland and the Aikengall II extension is likely to perform even better, due to higher wind speeds captured by the temporary meteorological mast and more efficient wind turbine technology.
“We are projecting over 40 per cent capacity, which compares favourably with some gas turbine generation and could make Aikengall II the most efficient large-scale wind farm in Scotland.
“Situating turbines in locations such as Aikengall II means they perform much better, we need fewer of them to meet our targets and they have less impact on towns and villages.”
The Renewable Energy Foundation, which publishes data on the energy sector, agreed that Aikengall was already a good performer, but said the comparison with gas plant was misleading.
Director Dr John Constable said: “Our own data, based on subsidy certificate claims and presumably very accurate, certainly suggests that Aikengall has performed well in comparison with many sites.
“This puts it in the top 15 sites, though others attain figures in the higher 30s [per cent], and one, the wind farm in North Rhins [near Stranraer] appears to have exceeded 40 per cent in 2011.”
However, he added: “It is somewhat misleading to compare these results with those of a conventional, fully controllable generator.
“Wind power stations sell all the energy they can generate, when the wind blows, but conventional power stations must follow the variations in daily and seasonal demand for electricity, and stabilise the system.”
The Scottish Community Foundation said that funding for community projects from wind farms was now well established.
It currently works with eight wind energy firms and more than 80 community councils which are benefiting.