(Adds final results, quotes from Pinera, supporter)

By Dave Sherwood and Felipe Iturrieta

SANTIAGO, Dec 17 (Reuters) - Conservative Sebastian Pinera won Chile's presidential election by a wider-than-forecast margin on Sunday, pledging to jump-start economic growth in the world's top copper exporter and opt for more business-friendly policies than his center-left predecessor.

Chile's electoral authority called the election for former president Pinera, who won 54.58 percent of votes compared with 45.42 percent for the center-left Alejandro Guillier, in a race that had been considered a toss-up.

In the end, the 68-year-old Pinera, who governed from 2010 to 2014, won more votes than any president since Chile's return to democracy in 1990. It was also the biggest ever loss for the center-left coalition that has dominated Chile's politics since the end of Augusto Pinochet's dictatorship.

Neither Pinera nor Guillier marked a dramatic shift from Chile's long-standing free-market economic model, but Pinera's victory underscores an increasing tilt to the right in South America following the rise of conservative leaders in Peru, Argentina and Brazil. He is due to be sworn in on March 11.

"Despite our great differences, there are large points of agreement," Pinera said of Guillier as his supporters waved Chilean flags in downtown Santiago. In the streets of Santiago's wealthy neighborhoods, where Pinera took some 90 percent of votes, residents blared their horns in support.

In his concession speech, Guillier called his nine-point loss a "harsh defeat" and urged his supporters to defend the progressive reforms of outgoing President Michelle Bachelet's second term.

Pinera defeated Guillier, a former TV anchorman and current senator, by painting his policies as extreme in a country known for its moderation, and likening him to Venezuela's socialist President Nicolas Maduro. Guillier had championed Bachelet's agenda of reducing inequality by making education more affordable and overhauling the tax code.

The investor favorite in the $250 billion economy, Pinera's proposals are seen as pro mining in a country where copper is king. He has pledged support and stable funding for Chile's state-run miner Codelco, and has promised to slash red tape which had bogged down projects under Bachelet.

The campaign exposed deepening rifts among Chile's once bedrock center-left, an opening Pinera leveraged to rally more centrist voters around his proposals to cut corporate taxes and double economic growth.

After a far leftist party made unexpected gains in November's first round, Pinera seized on the division, campaigning on a platform of scaling back and "perfecting" Bachelet's tax and labor laws.