Chavez counts former Cuban President Fidel Castro as a friend and mentor, and his opponent, Henrique Capriles, had promised to change a relationship he described as financing Cuba's political model.
"I'm sure it's a big sigh of relief (in the Cuban government), because what they faced under Capriles was a certain renegotiation, at minimum, of the oil deal," said Philip Peters, a longtime Cuba observer at the Virginia-based Lexington Institute think tank. "It would have been a tough blow."
Cuba was hit hard by the collapse of the Soviet Union at the dawn of the 1990s and subsequent loss of billions in aid, and Chavez's election in 1998 resulted in a welcome ideological and commercial friend.
With polls showing Chavez facing the most serious electoral rival of his presidency, the Venezuelan race has been a constant fixture in Cuban state media for the last month and a half. Campaign news led TV broadcasts, topped the fronts of newspapers and was endlessly analyzed on roundtable shows.
Cuban television devoted hours to the election results on Sunday, covering the late-night announcement of Chavez's 10-point victory and shortly afterward reading out a congratulatory note from Cuban President Raul Castro.
"Your decisive victory ensures the continuity of the struggle for genuine integration in our America," Castro said.
There was no immediate comment from Fidel Castro, who left office permanently in 2008 and is rarely seen in public these days.
Ordinary Cubans also greeted the news, keenly aware of the country's special relationship with a man who visited frequently even before he began receiving cancer treatment from Cuban doctors.
"For us, it is a joy," said Rosa Hernandez, a 45-year-old Havana homemaker.
"In practical terms, for Cubans it means the continuity of a relationship that could have been interrupted," said Leonardo Juan, a state-run business worker. "It means a strengthening of very close ties."
According to government statistics, Cuba and Venezuela did some $6 billion in trade last year, or around 40 percent of all Cuban trade in commercial goods, most of that comprised of Cuban imports of oil and derivatives.
The figure does not include the legions of Cuban doctors and other professionals performing services in Venezuela, but it still far outstripped Cuba's No. 2 commercial partner, China, which accounted for $1.9 billion in trade with the island in 2011.
Cuba and Venezuela have also joined forces to rehabilitate the Cuban port of Cienfuegos, where they operate a refinery together.
Six more years of Chavez also means Havana can continue to count on Venezuelan support in international politics, a reliable friend to bang the drum for Cuban interests in the region and its disputes with Washington.
"It ties into Cuban foreign policy too," Peters said. "Cuba and Venezuela have their alliance and their vision that they're trying to promote in the Americas."
Havana surely is not alone in its relief.
Nearly 20 Caribbean and Latin American nations, including tiny and struggling economies like Haiti, benefit from the Petrocaribe program under which Venezuela provides oil and natural gas at preferential prices.
"In the Dominican Republic, they were ecstatic. ... The Dominican economy probably would have collapsed without the generous terms of Petrocaribe," said Eduardo Gamarra, a Latin American studies professor at Florida International University.
"In the Caribbean, (Chavez) has all this collection of little countries who are not important in terms of the economy ... they survive because of these subsidies from Chavez," Gamarra said. "But guess what they also do: They vote. ... They will vote very disciplined with Chavez when it comes to an important U.N. vote, an important OAS vote, and Chavez knows that."
Peter Orsi is on Twitter at www.twitter.com/Peter—Orsi
Associated Press writers Andrea Rodriguez in Havana and Ian James in Caracas contributed to this report.