Formula 1 does not put a limit on engine power. It puts a limit on how quickly fuel can get into the engine: a maximum of 100 kilograms per hour, measured continuously.
Power is what comes out. Fuel flow is what goes in. Cap the input and you have capped the output without ever writing a horsepower number into the regulations.
It is one of the more elegant pieces of rule-writing in the sport, and in its first season it got a driver disqualified from a podium.
Why does F1 limit fuel flow instead of power?
Because a race fuel limit on its own does not do the job.
Since 2014 there have been two separate fuel restrictions: a total allowance for the race, and an instantaneous flow limit of 100kg per hour.
Without the flow limit, a team could hold back fuel through the parts of a lap where power matters less, then dump it in enormous quantities where it matters most. Same total consumption across the race, far more power exactly where it counts. The race allowance would be respected and completely defeated at the same time.
