IndyCar's Hybrid, Explained: The 60-Horsepower Boost Drivers Charge Themselves
Welcome to the Happy Hour Racing IndyCar Tech Breakdown - where we take one confusing part of IndyCar and make it make sense. No engineering degree required.
The Short Version
Since July 2024, every IndyCar has carried a hybrid system that recovers energy the car would otherwise throw away and hands it back as roughly 60 extra horsepower whenever the driver asks for it. It is not a battery, and it is not push to pass. The strange part, and the part that makes IndyCar different from Formula 1, is that drivers charge it themselves and choose when to do it. And four weeks ago, IndyCar turned the whole thing down.
What the Hybrid Actually Is
Two parts, and they live in one place. The first is the Motor Generator Unit, or MGU. It is one device doing two opposite jobs. Run it one way and it acts as a generator, stealing a little energy from the spinning driveline and turning it into electricity. Run it the other way and it acts as a motor, shoving that electricity back in as extra push. Same hardware, flipped around.
The second part is the Energy Storage System, or ESS. This is where people get it wrong. It is not a battery. It is a pack of 20 supercapacitors. A battery stores a lot of energy and gives it up slowly, like a water tower. A supercapacitor stores much less but dumps it almost instantly, like a bucket you can tip over in one motion. Racing does not need a big reservoir. It needs a hard shove out of a corner, right now. So IndyCar picked the bucket.
Both parts sit in the bellhousing, which is the housing that connects the engine to the gearbox. IndyCar's own rulebook defines the hybrid as the powertrain contained in the bellhousing, and the series has described the whole package as about the size of a milk crate. There is no big battery box anywhere on the car.
The Part F1 Fans Find Weird: Drivers Charge It on Purpose
In Formula 1, harvesting is largely automatic and the software runs the show. IndyCar handed the job to the driver.
The car does recover energy on its own under braking, and by reading the throttle when a driver lifts. But an IndyCar driver can also grab paddles and buttons on the steering wheel and command the system to charge whenever they want, including flat out down a straightaway. That is called regen on demand, and there is no free lunch: charging on a straight puts a drag on the driveline and slows you down a little right then, so you can go faster somewhere else. Deploying is a separate control, a latching button similar to the push to pass button drivers already knew.
So every lap is a puzzle. Where do I give up a little speed to bank energy, and where do I spend it. Alexander Rossi described watching rivals regenerate on the straights and then deploy through the corners to lift their average speed across the whole lap. He also put the stakes plainly: you can have the car balance perfect and the trim level perfect, and if your hybrid strategy is not, that can be the difference between third and 15th. Marcus Ericsson called it before the thing ever raced, saying the drivers with a lot of brain capacity would come out on top. Graham Rahal was blunter: there is a lot of thinking to do.
The Best Feature Has Nothing To Do With Speed
Before the hybrid, a stalled IndyCar was a dead IndyCar. It sat there, the AMR Safety Team drove out, and a race got neutralized because one driver spun and killed the engine. Now the MGU spins the engine back to life and the driver simply drives away. Fewer safety trucks, fewer cautions, fewer races decided by a yellow nobody needed.
One catch that gets missed constantly: this is a road and street course feature only. On ovals, IndyCar still sends the AMR Safety Team to every stalled car, because a car rejoining on its own at an oval is a genuinely bad idea. There was a growing pain, too. Colton Herta was penalized in 2024 for using the MGU to pull out of his own pit box before his crew was done. That incident pushed the series to rethink the pit lane rules, and self-starting in pit lane was allowed beginning in 2025.
Why IndyCar Turned It Down Last Month
Here is the current-season part most explainers have not caught up to yet. The hybrid has been failing. Alexander Rossi's Sonsio Grand Prix ended early with a hybrid failure in May. Scott Dixon's Detroit engine shut down in June. Across the first nine races of 2026 the series burned through so many replacement units that the spare pool started running dry.
Alexander Rossi's Sonsio Grand Prix race ended early due to a hybrid failure, leading him to criticize the system and IndyCar race control.
— IndyStar (@indystar) May 9, 2026
'That's frustrating' https://t.co/K9m9Thk6sj
So starting at Road America in June, IndyCar cut hybrid power by 10 to 25 percent, track by track, for the rest of this season. In the series' own words, the move is aimed to help reduce thermal load and aging of the ESS cells, which will help with robustness of the hybrid power unit, stabilize system fallout and assist with unit supply. Translation: the supercapacitors were cooking themselves, so the series backed off to make them last. IndyCar expects the lap time difference to be small enough to disappear into normal tire and temperature swing.
The drivers are not pretending to love it. Scott Dixon said that if you polled the drivers, it would be 100 percent, get rid of them. Rossi called it annoying to have a failure in the car because of a product the drivers did not ask for that does not improve the racing. That is unusually blunt talk about a piece of spec equipment, and it is worth knowing when you hear a hybrid failure called on the broadcast.
What You Will See On Track
Watch a road course restart and look for a driver who spins, sits for a beat, then simply drives off with no truck in sight. That is the MGU. Watch the timing screens on a long straight and notice a car that seems to give up a tenth for no reason, then rockets out of the next corner. That is regen on demand, paid for and cashed in. And when a car slows with no smoke and no contact, and the crew looks calm rather than panicked, there is a decent chance the bellhousing just quit.
The Bottom Line
Formula 1 hands harvesting to a computer. IndyCar handed it to the driver, then asked them to figure out where to spend it while also racing. That is the whole idea, and this season it comes with an asterisk: the system is turned down while the series keeps it alive. The 2.2-liter twin turbo V6 underneath, worth roughly 700 horsepower depending on boost, carries on until a new 2.4-liter formula and a bigger second-generation hybrid arrive in 2028.
If reading about the bellhousing made you want one on your shelf, the Colton Herta #26 Andretti 1:18 diecast is in stock, and Herta is the driver who found the pit lane loophole in the first place. There is more IndyCar gear over in the IndyCar collection, including the 109th Running Indy patch snapback and a few checkered flag tees. No pressure, we would rather you just enjoy the race.
