The French car marker has helped Red Bull clinch four consecutive drivers' and constructors' titles, and will again power the team in 2014 when turbo engines will return to F1.
Renault famously introduced a turbo engine in F1 back in 1977, becoming the first team to win with a turbocharged car two years later.
"Renault has got a great track record and we have achieved some phenomenal things with them," Horner told AUTOSPORT.
"They perhaps don't have the budget of some of the others but they have been prudent in how they spend it.
"We are pretty confident that we will have a competitive power plant.
"There's an awful lot a hearsay that goes round at this time of year but as always, what is important is what happens when the flag drops in Melbourne."
Horner said Red Bull's relationship with Renault means the French manufacturer will do everything possible to adapt its engine to next year's car.
"The status we have as their works partner means that the maximum effort is going into optimisation of the engine and the Red Bull car," he said.
"It's going to be a big element of grand prix racing next year.
"Renault has worked very closely with us on the installation of the engine and we have concentrated where they can.
"They [have their] specialist area, our area is the chassis, so it has been a collective effort over the last couple of years to integrate the engine."