The F1 hybrid system, explained: brake to boost
Every lap is a battery cycle: brake hard, bank the energy, then decide exactly when to spend it back.
By Indy GillWatch the throttle trace on any onboard replay this season and you'll catch the moment the graphic dips before the braking zone, not because of traffic, not because of a flag, but because the dash is telling the driver the battery is nearly empty and full throttle right now would be the slower option. That's the hybrid system doing its job in public.
The system is a loop. Kinetic energy that would otherwise vanish as brake heat gets converted to electricity, stored in a battery, then fired straight back at the rear axle as a power boost the internal combustion engine can't provide on its own. Formula 1 calls the whole package the ERS, the Energy Recovery System, built around a motor generator unit on the driveline (MGU-K) and, until this season, a second one bolted to the turbocharger shaft (MGU-H). The battery itself has an FIA name too: the Energy Store.
It matters because this loop is no longer a bolt-on. Electrical power used to supply roughly a fifth of a power unit's output; the 2026 rules pushed that toward half, which means a driver who mismanages the loop isn't losing a nice-to-have boost, they're losing half the car. The old units drew around one-fifth of their total power from the electrical side; the target for this generation of engine is to push that closer to fifty-fifty between petrol and battery.
The two-motor loop that ran from 2014 to 2025
For twelve seasons the harvesting side had two separate jobs working in parallel. Under braking, the MGU-K pulled kinetic energy off the driveline and pushed it into the battery. Meanwhile the MGU-H lived on the turbo shaft itself, doing double duty: any exhaust energy that would otherwise be dumped through the wastegate got skimmed off and turned into electricity, and the same unit could work in reverse, spooling the turbo up before the driver even asked for throttle so there was no lag to hide.
The two units weren't treated equally by the regulations, and that asymmetry is the whole reason energy management became a driver skill rather than an engineer's afterthought. The MGU-K had a hard ceiling, capped at 120 kW of deployment and a strict 2 MJ harvested and 4 MJ deployed per lap, while the MGU-H answered to no such limit and could shuttle energy to and from the battery all day long. That gap between a heavily-capped MGU-K and an uncapped MGU-H meant the turbo unit was doing quiet, constant top-up work all lap long, refilling a battery that the kinetic side alone could never keep full on a circuit with light braking. It's also why, historically, drivers effectively got one meaningful deployment window per lap rather than several small ones.
The 2026 rewrite: one motor carrying the whole hybrid load
This season tore that architecture up. The MGU-H is gone entirely, and the MGU-K has been scaled up to do the job both units used to share. Deployment power from the single remaining motor has nearly tripled, jumping from 120 kW to 350 kW, specifically to sharpen overtaking and top speed now that the turbo's free electricity has vanished. The FIA's own reasoning was partly cost, partly relevance: the MGU-H had no equivalent in road-car technology and was one of the biggest barriers stopping new manufacturers joining the grid.
With the turbo's free top-up gone, everything now runs through braking and lift-off events, and the ceilings have moved to compensate. The battery can now bank up to 9 MJ of recovered energy per lap, double the old limit, which is a genuinely huge chunk of energy to be handling purely through braking and lift-off, the sort of jolt you'd need to hurl a loaded family hatchback up to motorway speed from a standing start. Deployment has changed shape too. Rather than one release valve per lap, the car can now fire several bursts, each drawing the battery down hard: a single burst can spend up to 4 MJ, which is close to twelve seconds of the electric motor running at full power, and a car can take as many of those bursts in a lap as its battery can actually sustain, not just one. There's also a fresh tactical layer built specifically for wheel-to-wheel moments: a driver within a second of the car ahead at the detection point can trigger an overtake boost, unlocking a further half a megajoule of recharge and a taller power ceiling to hold that speed longer through the move.
Why lifting off can be faster than flooring it
Here's the counterintuitive part a casual fan feels but rarely has named for them: sometimes the fastest way round a lap involves easing off the throttle when nobody's forcing you to. The battery only refills through braking, coasting, or a light-throttle trim, so a driver who spends every available watt early risks arriving at the next big straight with nothing left, and an F1 car running on internal combustion alone is a different, slower animal than one running the full hybrid package.
Teams now have named techniques for exactly this trade-off. Lifting off the throttle a fraction early into a corner buys extra harvesting time at the cost of some entry speed, and it closes the car's active-aero flap early too, so the driver is trading a sliver of straight-line efficiency for battery charge. The other tool, known in the paddock as super clipping, works the opposite way round: the driver stays planted at full throttle right to the end of the straight and only trims the electric contribution for a beat, so the active aero never has to close and the car keeps its low-drag shape the whole way down. Get the balance wrong and you get clipping in the bad sense, the car simply running dry of electric assist mid-straight and losing raw speed exactly where it's most visible. Watch a car go noticeably softer on top speed with no obvious reason and there's a decent chance you've just watched a flat battery, not a tow that ran out.
That's the calculus running in an engineer's head every single lap: not "how fast can this car go right now" but "what does the battery need to look like in ninety seconds, at the corner where the move actually happens." A driver who bags the fastest theoretical sector by holding the throttle a beat too long can arrive at the real overtaking zone with an empty tank and get eaten alive by a rival who lifted early three corners back.
Where you'll actually see this play out
Watch the battery percentage graphic broadcasters now overlay on selected cars and you're watching this loop in real time. Radio calls asking for a specific "recharge mode" or complaining about "no energy" out of a corner are drivers and engineers talking through exactly the trade-off above. Low-braking circuits, the Monza-style tracks with long, flat-out sections and few heavy stops, are where the battery struggles hardest to refill, and you'll see more visible lift-and-coast there than at a stop-start street circuit where braking zones do the harvesting for free.
Understanding this loop also reframes what "overtake mode" and defensive driving mean in 2026. A driver defending isn't just holding a racing line, they're deciding whether to spend their last reserve of boost now or save it for the DRS zone that used to be automatic and now isn't.
For the mechanics of each half of this loop in more depth, the individual explainers on the MGU-K, the now-retired MGU-H, and the Energy Store itself go deeper on the hardware; the wider ERS and power unit explainers cover how this all bolts onto the rest of the car.