BMW Sauber team boss Mario Theissen says his squad is not yet sure if KERS will return to its car for the British Grand Prix.
The German squad was one of the primary advocates of the regenerative device, and one of the few teams to use KERS at the start of the season.
But when BMW introduced major revisions of its chassis to include its own version of the double diffuser, it temporarily shelved KERS as it would not have been able to package the system properly in the dramatically different car.
BMW initially planned to use KERS again from Turkey, but decided to postpone its reintroduction so that it could properly analyse how the aerodynamic upgrades performed. It is also uncertain whether to use the device in Britain.
When asked whether KERS would be back for Silverstone, Theissen replied: "Not definitely. We will discuss it now next week, and then decide."
He said it was difficult to determine what effect the system would have on the revised car without being able to test.
"What we can quantify is the lap time advantage that you get on the straight," said Theissen. "What we cannot quantify is the difficulties that you experience on Friday trying to put all the things together."
FOTA announced on Sunday that it had agreed to shelve KERS next year, a decision that Theissen said he fully accepted despite his team's enthusiasm for the technology.
"We have voted in favour of KERS but as all the other FOTA decisions so far we will go with the majority," he said.
Despite the uncertainty over KERS, Theissen is confident that BMW is now making progress back up the field and is optimistic about the British GP.
"I think what we have seen here is a solid step forward so it should work as well at Silverstone," he said.