Horner has laid part of the blame for the fact Red Bull are currently lagging behind the likes of Mercedes and Ferrari at the door of power-unit supplier Renault, and in particular the new-for-2014 ERS (energy recovery system).
As part of the latest revamp of the regulations, the ERS features two motor generator units that store wasted energy under braking and from the turbo, providing an additional 33-second power boost.
Up until this season Renault, as an engine manufacturer, had barely played any part in developing the old KERS (kinetic energy recovery system) when that was introduced in 2009.
Flavio Briatore, as team principal of the former Renault team that is now Lotus, took a decision back then that KERS would be developed in-house rather than by the French company.
When Renault, as an F1 team, exited the sport soon after and simply became an engine supplier, there was a knock-on effect.
It resulted in Red Bull, as a Renault customer, having to develop their own KERS unit, as they have done for the last three years.
But with the introduction of the power units, that incorporates ERS, development has switched to the engine manufacturers themselves, and that has left Renault playing catch up.
Horner said: "If you look at the situation at Renault, Flavio made the decision years ago that energy recovery and KERS would be dealt with by the race team, not the engine manufacturer.
"Renault then sold the race team and we picked up KERS and developed our own system that we ran within the gearbox.
"Now, on the new powertrain, energy recovery has gone back to being the responsibility of the engine supplier.
"That is where it should sit, but they (Renault) have had a steeper learning curve than perhaps Mercedes or Ferrari who have a few years of experience."
Horner concedes Red Bull's engineers have had to provide a helping hand to those at Renault.
Speaking to Autosport, Horner added: "We have been supporting them with our experience on the whole energy recovery side of the package.
"That's where we can contribute the most and that's where the biggest issues are at the moment.
"We have had a limited involvement, and are getting more and more involved."