Horse Powertrain, the Renault-Geely joint venture founded in 2023-2024 to develop next-generation low-emission powertrains, has presented a new ultra-compact range extender system at IAA Mobility 2025, the Horse C15.
Why does it matter? REEVs (Range-Extended EVs) offer a pragmatic middle ground between battery-only and hybrid drives, with a gasoline engine used as a generator only to produce electricity. It allows for extending the range of an EV substantially without adding large, costly battery packs.
Briefcase-size
“No larger than a briefcase, Horse C15 integrates an engine, generator, and inverter into a unit compact enough to be fitted within existing battery electric vehicle (BEV) platforms with little to no modification,” Horse Powertrain claims.
“This allows OEMs to easily and efficiently convert a BEV platform into a range extended EV (REEV), allowing them to expand their product line-ups to meet local market demands.”
Horse Powertrain presents itself as a global powertrain supplier, similar to Bosch, Magna, or Continental, not just an internal supplier to Renault and Geely. The Horse C15 is explicitly designed as a “plug-and-play” solution for multiple OEMs.
Half of the battery cost
The C15’s sweet spot is budget cars, small EVs, and light commercial vehicles, where a big battery is too expensive, but buyers still want long range. The cost of today’s EVs is dominated by the battery pack, which represents 20 to 40% of the total vehicle cost.
Large packs (80 to 100 kWh) are expensive and sensitive to lithium prices (LFP), and rare metals like nickel and cobalt (NMC batteries). REEVs with something like Horse C15 can use a smaller, cheaper battery (40-50 kWh) while still delivering long range.
The compact extender, which measures just 500 x 550 x 275 mm in its naturally aspirated version, adds cost, but it’s far less than doubling battery capacity.
How does it work?
The C15 is a series hybrid range extender. The engine never drives the wheels; instead, it spins a generator at a steady RPM. That generator produces electricity to recharge the battery or directly power the e-motor if needed.
Because the engine doesn’t follow accelerator pedal input, it can run only at its most efficient speed and load, which means lower emissions and fuel use compared to traditional ICE driving.
Horse hasn’t published exact curves yet, but based on similar extenders like the pioneering BMW i3 REx, the GM Volt genset, or Nissan e-Power, it typically operates in a narrow band around 2,000-3,500 rpm, where efficiency and NVH (noise, vibration, harshness) are optimal. This “fixed-RPM window” means the engine runs quietly and avoids inefficient revving cycles.
It is designed for Euro 7 compliance (including China 7 and SULEV 20), the press release states. “Horse C15 will be available in naturally aspirated form for B- and C-segment vehicles, with maximum engine power of up to 70 kW.”
“For larger D-segment vehicles and LCVs, the addition of a turbocharger increases power output up to 120 kW.” The unit will be able to run on gasoline, ethanol, and methanol flex fuels, and synthetic fuels as well.
What about fuel consumption?
Horse says the C15 is tuned for efficiency at a constant load, but detailed g/kWh numbers are not yet public. Claimed to be more efficient than small 2-cyl units thanks to steady-state tuning, this is likely to be 220 to 240 g/kWh brake-specific fuel consumption (BSFC), which translates into 30 to 35% efficiency, depending on fuel type.
In practice, this would mean 5 to 6 liters/100 km equivalent when driving purely on the extender, but since most daily driving is electric, average consumption is far lower.
To compare, the BMW i3 REx (0.65 liters, 2-cyl) uses 0.6-0.7 liters of gasoline per 10 km when the range extender is running, which means 6 to 7 liters/100 km when the battery is depleted.
Lifetime CO2 footprint?
And how does the REEV compare to a fully electric BEV over its entire lifespan? The C15 generator is a practical transitional technology, cutting battery size, lowering the production CO2 footprint, and solving the general public’s ‘range anxiety’, but it won’t beat BEVs in long-term sustainability once charging infrastructure is universal.
Regions with weak charging infrastructure, such as those in southern or eastern Europe, with cost-sensitive markets, and vehicles that require high uptime, like vans, are likely to benefit the most from the C15 technology. Still, it is the next-best alternative to the BEV, considering its environmental impact from cradle to grave, as assessed by the standardized Life Cycle Assessment (LCA).
Life-Cycle CO₂ Emissions (g CO₂-eq/km over lifetime)
| Vehicle Type | EU (clean grid) | US (mixed grid) | China (coal-heavier grid) |
|---|---|---|---|
| BEV (75 kWh battery) | ~70–90 | ~140–160 | ~180–220 |
| REEV (40 kWh + C15 extender) | ~95–110 | ~150–170 | ~170–200 |
| OHEV (Nissan e-Power) | ~120–150 | ~150–180 | ~170–210 |
| HEV / PHEV (real-world use) | ~140–170 | ~170–200 | ~190–230 |
| Conventional ICE (gasoline) | ~200–220 | ~220–250 | ~240–270 |
OHEV are ‘Optimized Hybrid Electric Vehicles’, used by brands as Nissan (e-Power) or Honda (e:HEV). OHEVs burn fuel all the time, since their small battery (2 to 5 kWh) can’t cover daily commutes. REEVs burn fuel only occasionally on longer trips, resulting in lower lifetime CO₂ emissions if users charge regularly.
Compared to BEVs, there are still other tailpipe emissions, such as NOx, small particles, and CO, but they’re tightly controlled. Meeting Euro 7, China 7, and SULEV 20 emission standards means the C15’s emissions should be comparable to the cleanest combustion engines on the road today.
