With testing prohibited during the season, the teams have only a few track sessions left to satisfy themselves that their systems are reliable and safe. If in doubt, they could leave them out.
Most are reserving judgment, with even those considered furthest down the road on development still facing plenty of hurdles.
"We definitely haven't decided (whether to use KERS)," Williams technical director Sam Michael told Reuters. "The jury is still out on whether we start with it or not, not so much from a performance point of view, but more about reliability.
"It's about making sure we get the reliability worked on. That's the big challenge."
Formula One is divided between those, such as BMW-Sauber, who welcome KERS as a ground-breaking challenge and others who spit out the four-letter word with some resentment.
Renault team boss Flavio Briatore is in the latter camp, detecting potential danger and a gross waste of money at a time when the focus is on cutting costs in the face of global recession.
"I think it is a terrible mistake," the Italian said at the launch of his team's new car in Portugal last week.
Formula One's commercial supremo Bernie Ecclestone, at loggerheads with the governing body on a number of issues, agreed. "I have always been against KERS," he said recently. "It costs a lot of money when we are trying to save it." More at Reuters