Formula 1’s 2027 power unit rules will increase the usable battery energy window from 4 MJ to 4.5 MJ, before a further rise to 5 MJ in 2028. Combined with lower peak MGU-K deployment, greater energy recovery and increased internal combustion engine power, the change is intended to make battery management less critical and reduce the power unit’s sensitivity to how drivers use the throttle around different circuits.
The technical revolution introduced in 2026 is therefore already set to evolve from next season. Less than half a championship has been enough for the teams, the FIA and Formula 1 to conclude that the original concept required revision, moving gradually away from the equal 50-50 division between electrical and combustion power that was supposed to define the beginning of the new regulatory cycle.
Why the original 2026 power unit formula required an early revision
One point needs to be made clear: the original formula was not inherently wrong. The main problem was that it did not possess all the tools required to sustain itself effectively under every operating condition.
The removal of the MGU-H placed greater responsibility on the battery and MGU-K, while the permitted battery energy window remained essentially unchanged from the previous generation of power units. The FIA was consequently forced to accept compromises when defining the aerodynamic regulations, because the amount of drag and downforce generated by the cars directly affects how much electrical energy must be deployed and recovered around a lap.
The same relationship will remain important in 2027. Before the 2026 season has even reached its halfway point, some teams have already exceeded the downforce values that had originally been predicted for the end of the year. That demonstrates how much performance remains available through development, a subject that has also become increasingly important across Ferrari’s latest technical analysis.
For that reason, the FIA has approved aerodynamic modifications for next season that are intended to reduce downforce and ease the demands placed on the power unit. Those changes, which will be examined separately in greater detail, will accompany a series of progressive engine revisions designed to reach a 60-40 split in favour of the internal combustion engine by 2028.
In 2027, the ICE is expected to produce approximately 420 kW of maximum power, representing an increase of around 20 kW compared with the current figure. It should then rise to 450 kW in 2028, a step made possible by a 13 per cent increase in the permitted fuel-flow rate.
MGU-K deployment will fall as energy recovery increases
Those will not be the only significant changes. Some of the most important revisions concern the electrical side of the power unit.
As already established, the MGU-K’s maximum deployment power will fall from the current 350 kW to 300 kW. Reducing the highest deployment peak should make the system less energy-intensive at maximum output, while allowing teams to distribute electrical power more effectively along the straights and across an entire lap.
At the same time, maximum recovery power will increase. The limit will rise to 375 kW in 2027 before reaching 400 kW in 2028. By that stage, the electrical system will be capable of recovering 50 kW more than under the original 2026 specification.
These changes are significant because they are connected to other revisions that have received less public attention from Formula 1 and the FIA. Together, they will alter how teams harvest, store and deploy electrical energy around a lap, beginning with the permitted energy window of the battery.
F1’s 2027 battery energy window will increase to 4.5 MJ
The battery energy limit was one of the few major elements that did not change between the previous and current technical cycles. Both the 2025 and 2026 regulations set a maximum difference of 4 MJ between the battery’s highest and lowest permitted state of charge while the car is on track.
This does not necessarily mean that the physical battery pack is incapable of holding more energy. Instead, the 4 MJ figure represents the maximum usable state-of-charge variation allowed by the FIA during a session.
Reducing car weight was understandably one of the principal objectives for the 2026 regulations. The permitted energy window could have been increased immediately, but a larger battery risked adding mass, which would have contradicted the wider effort to make the new generation of cars lighter.
Formula 1 and Formula E batteries also have very different characteristics. Concepts cannot automatically be transferred from one championship to the other because the cars use, recover and deploy energy in fundamentally different ways.
Limiting peak electrical loads should also reduce stress and degradation within the power unit. The governing body’s original intention was to restrict each driver to only two power units for an entire season, before the allocation was increased to three to provide teams with at least some operational flexibility.
Although the units have changed physically, running 350 kW during both deployment and recovery inevitably places substantial stress on the system. The demands involved in managing that energy have already influenced how teams operate the new engines, including the energy-management concerns surrounding Ferrari’s SF-26.
More stored energy and lower deployment peaks provide greater flexibility
From 2027, the situation will change. If the power unit can recover more energy, it also needs more space in which to store it. Otherwise, increasing the maximum recovery rate would deliver limited practical benefit whenever the battery approached its permitted state-of-charge ceiling.
The usable battery energy window will therefore increase by 0.5 MJ next season, rising from 4 MJ to 4.5 MJ. It will then expand again to 5 MJ in 2028.
It is not yet clear whether the FIA will leave the maximum energy limits per lap unchanged. Those limits currently help prevent extreme superclipping, where electrical deployment falls away sharply before the end of a straight, and discourage teams from pushing drivers towards excessive lift-and-coast techniques simply to manage the battery.
Regardless of the final per-lap limits, a larger energy window combined with a lower deployment peak should allow teams to spread electrical power more effectively along the straights. The MGU-K should be capable of remaining active for longer rather than delivering a very high peak before rapidly exhausting the available energy.
Why the power units should become less sensitive to throttle use
The revised specification should also make power-unit behaviour less dependent on the driver’s use of the accelerator pedal. With the current high deployment peak, the exact moment at which a driver returns to full throttle can have a major influence on the way electrical energy is consumed.
Depending on the circuit, delaying or anticipating throttle application at corner exit can significantly change the power unit’s energy profile. That sensitivity means the most natural driving technique is not always the most efficient one, an issue explored further in the analysis of how energy deployment is affecting driver control in 2026.
At certain tracks, the current power units make it more efficient for drivers to attack the braking and corner-entry phase before delaying throttle application on exit. This can feel almost unnatural because it prioritises preserving electrical energy for the straight rather than immediately maximising traction out of the corner.
The objective is to avoid wasting too much electrical power while the car is still traction-limited and instead use more of it once the car is travelling in a straighter line. At other circuits, where the corner and straight profiles are different, this effect is less influential. The variety of layouts on the 2026 Formula 1 calendar helps explain why the same power unit can behave very differently from one weekend to another.
Aerodynamic development remains closely connected to energy recovery
All these factors will continue to interact with the aerodynamic development of the cars. The FIA will intervene for 2027, but teams will inevitably continue finding additional downforce as their understanding of the regulations improves.
More downforce generally means greater aerodynamic resistance and fewer opportunities to recover energy efficiently. Teams will consequently need enough battery capacity to store energy whenever harvesting conditions are favourable, which is another reason for expanding the usable state-of-charge window.
The connection between aerodynamic load and power-unit demand has already become visible during the opening part of the regulatory cycle. Ferrari’s performance at the Hungaroring, for example, demonstrated why downforce alone did not explain the SF-26’s limitations in Hungary.
Development will not stop merely because the FIA reduces the initial load targets. Teams will continue to recover performance through new floors, wings and bodywork concepts, just as Ferrari intends to maintain its race-by-race development programme rather than waiting exclusively for major upgrade packages.
Recharge limits will change for starts, Safety Cars and qualifying
Some of the confirmed limits will also become more permissive in specific situations. Drivers will be allowed to recover up to 10 MJ during the formation lap, reducing the risk of reaching the regulatory recharge limit before the start and then finding themselves with restricted boost when the race begins.
The same principle will be applied behind the Safety Car. During 2026, there have been restarts in which cars were unable to prepare the turbo fully because they had already exceeded the permitted recharge limits while circulating at reduced speed.
Changes will also affect qualifying out-laps. At present, the preparation phase before a flying lap can involve a complicated series of procedures designed to place the battery and turbo in the correct operating condition. More permissive limits should simplify that process and reduce the chance of a driver beginning a qualifying lap without the intended level of electrical deployment.
FIA has not published the new MGU-K speed curves
One important detail remains unavailable to the public. The FIA has not yet released the curves that will define how much electrical power may be used according to the car’s speed.
Until this season, the technical regulations contained publicly accessible formulas determining the permitted MGU-K power at different speeds. These curves were designed to control energy consumption and prevent teams from using maximum electrical output without restriction across an entire straight.
Modified versions of those formulas will remain part of the regulations in future. However, they will be incorporated into a separate document that, for the moment, can only be consulted by the teams.
The increase from 4 MJ to 4.5 MJ in 2027 is therefore not an isolated battery change. It forms part of a wider attempt to create a more sustainable balance between recovery, storage and deployment. With a larger usable energy window, reduced deployment peaks and stronger recovery, Formula 1’s power units should become more flexible across different circuit layouts and less dependent on highly specific throttle-management techniques.
The process will continue in 2028, when the battery window rises to 5 MJ, recovery reaches 400 kW and the regulations move towards the planned 60-40 balance in favour of the internal combustion engine.
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