The Spaniard returned to single-seaters in 2014 after two years racing in the DTM with Mercedes, and he won three races to fight for the FR3.5 championship with the inexperienced Zeta Corse team.
While his 2014 campaign could be considered a good foundation for another title push this year, Merhi told AUTOSPORT that he would like to move on from the series.
"It's a pretty hard situation, but I don't plan to stay [in FR3.5]," said Merhi, who made three Formula 1 free practice appearances with Caterham late in the year.
"We had a really strong year, and I feel ready to do the next step.
"I don't feel comfortable to stay for another year."
Merhi paid tribute to the efforts of the Russian-owned Zeta squad, which he took to fourth in the teams' standings.
"This team more or less is new," he added. "They are up against experienced professional teams like DAMS and Arden, and it's good that we can fight with them.
"The year overall has been really good, and to get to the last round of the season fighting for the championship is very good."
Merhi went into the final weekend of the FR3.5 season with an outside chance of snatching the title from Carlos Sainz Jr, and he admits that it was an opportunity missed as his fellow Spaniard failed to score all weekend at Jerez.
"It's a shame that we didn't score any points at Jerez, I feel bad for that," Merhi said.
"We missed our chance. It was possible to do something and put Carlos in a hard situation.
"But it was a nice championship fight, and I'm happy with the year I had."
The 2015 Formula Renault 3.5 season will be notable for being the last with the French company's backing but also produced a worthy champion in Oliver Rowland. PETER MILLS evaluates this year's crop of drivers
Last year's field was extraordinary and hard to match, but the Formula Renault 3.5 grid will still have plenty of talent this season. Glenn Freeman runs through the field ahead of this weekend's season opener
Landing the Fortec seat that took rising star Robin Frijns to the 2012 FR3.5 title was already a good sign for Stoffel Vandoorne. Then McLaren took him under its wing. Peter Mills tells Vandoorne's story so far