Horse Powertrain, via its Horse Technologies division, and Repsol have unveiled a next-generation hybrid powertrain that they say achieves ultra-high efficiency and low fuel consumption, operating on 100% renewable gasoline.
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The development comes as the auto industry in Europe eyes a longer phase-out timeline for fossil fuel powered new vehicles, including hybrids.
The Horse H12 Concept engine introduces enhancements to the combustion system and reductions in internal losses, achieving 44.2% peak brake thermal efficiency (BTE) while reducing vehicle fuel consumption by 40% (in comparison with 2023 average passenger car new registration in Europe)1 to below 3.3 litres per 100 kilometres, according to standardised European testing (WLTP).
Maximizing efficiency directly results in lower fuel consumption and lower CO2 emissions in equal proportions, the companies claim. They say that when using the 100% renewable fuel, a mid-sized car equipped with the Horse H12 Concept powertrain and driving an average of 12,500 kilometres per year, will emit 1.77 tons of CO2 per year less than a vehicle with a traditional fuel and combustion engine.
The hybrid powertrain system incorporates the Horse H12 Concept engine, an evolution of the HR12 engine that includes an innovative combustion system designed at a 17:1 compression ratio, a new-generation exhaust gas recirculation system (EGR), an optimized turbocharger, a high-energy ignition system, and an improved hybrid gearbox with optimized energy management, as well as reduced internal friction enabled by new Repsol lubricants.
The project, led by teams from the Horse Technologies Division in Valladolid and the Repsol Technology Lab in Madrid, has produced its first two prototypes and validated performance. The first demonstrator vehicle is expected to be presented in early 2026.
This, the companies say, is the first step towards industrial production of highly-efficient hybrid engines.
The project, they point out, contributes to the mobility sector’s transition to net zero, applying the principle of technology neutrality, and demonstrates how innovation can provide near-term CO2 reduction solutions.
Horse points out that more than 97% of Europe’s current vehicle parc (ACEA) is still combustion-based, so delivering solutions capable of reducing CO2 emissions today – such as highly efficient engines and alternative fuels – play a complementary role alongside electrification, hydrogen, and other emerging technologies on the road to mobility net zero.
For these solutions to scale, it is essential that the current revision of CO2 standards for light-duty vehicles includes a clear, long-term framework. It should recognise the role of highly efficient engines powered by renewable fuels in road-transport decarbonization, ensuring a technology-neutral approach beyond 2035 to support innovation and necessary industrial investments.
Luis Cabra, Executive Managing Director of Energy Transition, Technology, Institutional Affairs and Deputy CEO of Repsol, said: “This collaboration shows that decarbonisation can be accelerated through innovative and accessible technological solutions. The use of 100% renewable fuels is a net zero emission solution, complementary to electric vehicles, for decarbonising the transport sector. Supporting clear and ambitious regulation that drives investment in renewable fuels and highly efficient engines is essential for Europe to reduce transport emissions faster in a more competitive and effective manner.”
Patrice Haettel, Chief Operating Officer at Horse Powertrain and Chief Executive Officer at Horse Technologies, adds: “The Horse H12 Concept is an example of how highly efficient engines and renewable fuels can reduce emissions today, without waiting for future solutions. As a company, we believe that relying on a single technology is not the fastest way to cut emissions. This is why we advocate a technology neutral approach that enables innovation across all solutions – electric, hybrid, range extenders and low-carbon fuels.”
In October, Repsol achieved a technological milestone by producing gasoline of 100% renewable origin at industrial scale at its Tarragona facility. This new product is compatible with existing gasoline vehicles, with no modifications required. Nexa 95, Repsol’s highest-quality 95-octane renewable gasoline, is already available at 30 service stations in Spain.
The company also offers renewable diesel at close to 1,500 service stations in Spain and Portugal, making it the largest distribution network of renewable fuels in Europe.
Repsol is the leading producer of renewable fuels in the Iberian Peninsula with the first industrial plant dedicated to the production of 100% renewable fuels from waste, in Cartagena (Spain). The company will start operations at a second plant in Puertollano in 2026. Additionally, Repsol will also launch a demonstrator e-fuels plant in Bilbao in 2026.
