“This is a happy day in difficult times,” said Mr Macron after taking a boat ride to the offshore Saint-Nazaire site.
But he added: “This took more than 10 years. That cannot be entirely satisfactory. We have to reduce delays.”
The offshore wind farm is France's first, but Mr Macron has set a goal of building 50 by mid-century to enable a huge expansion of domestic electricity production.
France has long relied on its large fleet of nuclear power stations to produce electricity, but many have been down for maintenance in recent months, exacerbating the energy crisis linked to the war in Ukraine.
A draft bill to be presented to the Cabinet next month would aim to speed up future renewable projects by dealing with local objections more quickly and connecting them to the grid as soon as they are ready.
“We need a massive acceleration,” Mr Macron said. “I want us to go at least twice as fast for renewable energy projects. Our neighbours often managed to do more, better and, above all, faster.”
Addressing the Russian gas cuts that have led to high prices across Europe, he said: “For the first time, energy has become a weapon of war.”
France aims to offset the shortages with a plan for “energy sobriety” that aims to reduce consumption of gas and electricity by 10 per cent over the next two years.
Mr Macron announced backing in February for a new generation of nuclear power plants, and electricity company EDF aims to restart most of its existing reactors by the end of December.
In the longer run, the new measures aim to reduce delays in building offshore wind farms from 10 to 12 years now, to about six years, and large solar farms from six years to three years, Mr Macron said.
The new wind park has 80 turbines and is located 12 kilometres off the coast of Brittany. Mr Macron was meant to formally open it on September 5 but was forced to reschedule due to bad weather.
The construction schedule also slipped back after former president Nicolas Sarkozy visited Saint-Nazaire in 2011 and said the wind farm would be up and running by 2020.