As argued by both BMW's Motorsport Director Mario Theissen and Renault's Technical Head Pat Symonds, it would be useless to fit their cars with KERS on the Monte Carlo street circuit, as it's dominated by low-speed corners and lack of long straights. Therefore, the charging and deployment of the unit would not be very effective.
When hearing rivals McLaren and Ferrari are considering the unit for the aforementioned race, Symonds commented: “I would like to see the simulation (showing) that in Monaco you are faster with KERS,” as quoted by Germany's Auto Motor und Sport.
Renault have already announced they've scrapped KERS from their F1 campaign until September this year, as they'll focus more on the development of the double diffuser and other aerodynamic tweaks in the meantime. In addition, they argued most of the tracks to Italian GP's Monza are not compliant with the characteristics of the unit.
BMW Sauber, in turn, have confirmed that a newly-developed KERS unit will make its way into the F1.09 from as early as the Turkish Grand Prix, scheduled on June 5. According to Theissen, the technology has been updated for the European rounds of the F1 calendar, but was left aside during the Spanish Grand Prix as the team wanted to fully focus on their new aerodynamic package.