Voters have endorsed a new energy law that aims to promote renewable energy, ban new nuclear power plants and lower energy consumption.
Final results show just over 58% of voters on Sunday coming out in favour of the Energy Strategy programme.
Supporters said the result is a "historic step for Switzerland", while opponents have warned of a shortage of energy supplies in winter.
The places closest to the country's five nuclear reactors, where residents would arguably have the most to lose with their shutdown, rejected the reform with clear majorities.
According to Claude Longchamp of the leading GfS Bern research institute, voters put their faith in the arguments of Energy Minister Doris Leuthard and the government over those of the opponents.
"After six years of debate in parliament and at committee level, a new chapter in Switzerland's energy policy can begin," said Leuthard at a news conference. "But there is still a lot of work to do."
She said efforts had to be increased to improve energy efficiency of buildings. She also said the country had to find solutions for the loss-making hydropower utilities and that underground storage sites for spent nuclear power rods still had to be found.
Energy Strategy 2050
The Energy Strategy 2050external link was approved by parliament last year, but the rightwing Swiss People's Party challenged it to a nationwide vote. The reform was also opposed by parts of the Swiss business community and some environmental groups.
Felix Müri, one parliamentarian opposed to the amended law, said on Sunday he is convinced the price of the reform is much higher for consumers than predicted.
The government initiated the policy change following the 2011 nuclear accident at Fukushima in Japan.
The output of solar, wind, biomass and geothermal energy will be increased and hydroelectric utilities can hope for additional subsidies.
May 21 vote
Nuclear power will be phased out gradually, starting in 2019. The country’s five reactors will be shut down if no longer deemed safe by the nuclear watchdog.
Nuclear power accounts for about 38% of energy produced in Switzerland.
Supporters said the law will make Switzerland less dependent on energy imports while maintaining its high supply standard. They argued it will also help reduce Switzerland’s energy-related environmental impact.
But opponents have warned of a potential energy shortage, and high costs for consumers as well as excessive bureaucracy.
During the campaign in the run-up to Sunday's vote, both sides accused each other of presenting misleading figures about the price an average household will have to pay if the strategy is implemented, ranging from an increase of CHF40 ($40.7) to CHF3,200 annually.
Nuclear and people’s power
It was the eighth time in recent history that Swiss voters had the final say on nuclear power in a nationwide ballot.
Last November, just over 54% of voters rejected a proposal to limit the lifespan of nuclear power plants to 45 years. This would have meant the end of nuclear energy production by 2029.
The issue is likely to remain on the political agenda regardless of Sunday's result.
Parliament is due to consider the introduction of special climate and electricity taxes as part of a second phase of the energy reform.
Earlier this week, a citizen’s committee started collecting signatures for a proposal to ban the production of nuclear power as well as financial participation in such power plants abroad exporting their output to Switzerland.
Campaigners have 18 months to collect at least 100,000 signatures to force a nationwide vote.