By Stefan Kristensen
January 11, 2022

Formula 1 ERS Explained

Formula 1 cars have always been cutting-edge examples of automotive technology, and modern-day Formula 1 racers are no exception. These cars contain tons of tech to help them race faster and more efficiently. Some of the newest examples of this technology are the ERS (Energy Recovery Systems), a form of hybrid technology.

In this article, we'll be going over the two types of ERS found in the current group of Formula 1 cars, and we'll explain how they work and what they do in detail.

ERS Overview

ERS has been used in some form or another in Formula 1 since 2009. While all ERS are the same in terms of their basic concept (they allow the car to save and use energy sources that would otherwise be wasted), their design has changed a bit since their creation.

The first ERS introduced to Formula 1 was KERS (Kinetic Energy Recovery System). KERS used either a flywheel or a battery to store the car's kinetic energy that would otherwise be lost during braking and supplement the engine's power when needed.

These days, Formula 1 cars use two different ERS: the MGU-H, which harvests thermal energy from the car's exhaust/turbo, and the MGU-K, which is an evolution of the original KERS.

Let's now take a look at these two systems and explain what exactly they do and how they work.


The MGU-H (Motor Generator Unit - Heat) is one of the two ERS found in modern Formula 1 cars. The MGU-H works in conjunction with the turbocharger and can function as either a generator or a motor depending on the situation. 

To better understand how the MGU-H works, it probably helps to know a little bit about how a turbocharger works if you don't already. Basically, a turbocharger consists of two main components, a turbine, and a compressor, that are joined by a shaft.

The turbine of a turbo is connected to the car's exhaust, while the compressor is connected to the intake. Exhaust gasses flow through the exhaust system and hit the turbine, spinning it. The spinning turbine, in turn, spins the compressor, which sucks in air and compresses it before sending it down the intake.

By providing the engine with more air, enables the engine to burn more fuel at once, which increases power. Turbocharging also assists with more complete combustion, so turbocharged engines are more fuel efficient than naturally aspirated engines.

Now, the MGU-H. In a Formula 1 car, the MGU-H is basically an electrical motor/generator that is attached to the turbocharger in between the turbine and the compressor. So the MGU-H contains a series of magnets, which spin around each other when exhaust enters the MGU-H. This is what actually generates electrical power. This power is then sent to the car's energy store, where it sits until it is needed again.

When the car is charging the battery, the car flashes red lights at the back of the car so the car behind is aware that the car ahead is harvesting energy and thus limited in power output which slows the car relative to cars not charging.

When the MGU-H functions as a motor, however, it isn't used to power the wheels; rather, it provides supplementary power to the turbo. When the driver steps on the gas pedal, it usually takes a second or two for the turbine to spin up; this is what's known as "turbo lag." While turbo lag occurs engine usually makes a lot less power than usual.

The MGU-H can compensate for this by using its alternative function as a motor to keep the turbo's compressor spinning even when the driver isn't on the gas. As a result, this more or less entirely eliminates turbo lag.

It's worth mentioning that these are the final years of the MGU-H in Formula 1; as of 2026, teams will stop using the MGU-H in their cars, mainly because the units are very complex and extremely expensive to use.


The MGU-K (Motor Generator Unit - Kinetic) is the second ERS used by Formula 1 cars. This ERS does basically the same thing as the MGU-H, but it works with different components of the car and is active at different times. 

The MGU-K is attached to the crankshaft, and when the driver is on the gas, the MGU-K acts as a small electric motor, adding its own power on top of the engine's power. When active, the MGU-K adds a maximum boost of up to 120KWH or equivalent of about an extra 161 horsepower to the car's total power output. The drivers can only use the MGU-K for a short amount of time each lap - approximately 33 seconds per lap.

When the driver steps off the gas or applies the brakes, the MGU-K switches its function and becomes a generator. Instead of powering the car, it uses the kinetic energy from the still-turning crankshaft to generate electrical power using magnets, much like the MGU-H. The resistance of the MGU-K also helps slow the car down slightly faster.

Energy Store - The F1 ERS battery

The Energy Store is F1-lingo for the lithium-ion battery used to store the harvested energy from the MGU-K and MGU-H. The battery weighs between 20-25 kilos.

The energy storage can deploy 4MJ per lap to the MGU-K, which provides an additional boost of up to 120KWH (161 BHP) to the Power Unit through the MGU-K. However, it can only recover 2MJ from the MGU-K per lap. But there is no limit on how much energy the ERS system can harvest from the MGU-H. This is so the manufacturers are free to utilize the maximum of this new MGU-H technology.

There is no limit on the maximum energy the battery can hold - so it can hold more than 4MJ. However, the difference between the maximum and minimum state-of-charge must not exceed 4MJ while racing. You might consider this a bit silly, but there is a good reason for this. It basically means that you do not need to change the battery immediately once it starts to deteriorate in storage capacity.

How Is ERS Used in a Race?

So, we know that ERS provides extra power to key components of the car. But in practice, how are these devices actually used? Are they always active, or can the drivers activate them whenever they want during a race?

Well, it's actually quite a complicated system depending on many things. The MGU-H is, in some ways, always active, as it's also there to eliminate turbo lag. And the MGU-K is harvesting energy while braking.

However, the harvesting and deployment of energy is actually very complicated. Because when is the best place to deploy energy through a lap? Or maybe you need to use the ERS tactically in a race to overtake or defend against a competitor?

Before the start of each race, teams choose what sections of the circuit they will activate the MGU-K and for how long it will stay active. Drivers don't have to use all of the power available to them in one go; for example, they can use 2 seconds of the MGU-K's power on one section of the track and 1 second of its power on another section.

However, during a race, some things can change quite fast, and you might need to deploy energy in certain situations to improve your chances of a great result. For instance, if you are in direct competition for position and need to overtake the driver in front, you might need to deploy the energy where you have the biggest chance of overtaking. And likewise, if you are defending against a driver that is trying to overtake you, you must perhaps deploy energy tactically so the other driver can get past you.

Therefore drivers have different modes they switch among during a race. These are what you hear race engineers refer to as "strat modes" or "SoC-modes" (State-of-Charge) to the drivers over the radio during a race. A strat-mode or SoC mode refers to predetermined power unit modes that the drivers can switch between. This varies a bit from team to team. But essentially, there are at least 3 different modes concerning the ERS system:

  • A mode where the ERS harvests more energy from the MGU-K and MGU-H than being deployed. Charging the battery
  • A neutral ERS mode where the amount of energy being deployed and harvested is more or less the same. And the battery level remains the same.
  • A mode where the ERS deploys more energy from the battery than being harvested. Sometimes referred to as "Party mode." or qualifying mode.

Typically the drivers also have an "Overtake" button that can give them a boost in specific situations where they need more power to overtake or urgently defend against a competitor.

Using the MGU-K adds another level of strategy to a race since it can give drivers an advantage over other drivers on certain track sections.

If the ERS components fail, teams might incur some penalties; read my post on engine penalties here.

Written by Stefan Kristensen
I have been passionate about motorsports ever since I was a little boy. Back then, I cheered on the racing cars simply based on their colors. Later I fell in love with the many technical features, strategic plays, humans and their stories that all together drives this amazing sport to make it as interesting as it is.
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