With automotive battery capacity currently scarce, expensive, and suffering supply problems, the deployment of this limited resource is critical to maximizing carbon dioxide reduction. And the most effective way to reduce global vehicle emissions for the foreseeable future is not full battery electric vehicles (BEVs), but mass adoption of hybrid vehicles.

That’s the conclusion from Emissions Analytics, the world’s leading independent specialist for the scientific measurement of real-world emissions. The global testing and data specialist that measures real-world emissions and fuel efficiency in vehicles says the slow adoption of BEVs, lack of infrastructure, and concerns around an economical supply of batteries mean that the best way to reduce emissions would be to optimize the industry’s available battery capacity thus recommending the prioritization of hybrids now over full-electric vehicles in the future.

This finding was backed up by extensive real-world testing where they’ve found that hybrids, whether in gasoline or diesel form, offer the highest emissions reduction per kWh across all electrified powertrains.

Using mild, full, and plug-in hybrid real-world emissions test data, from both European and US vehicles, Emissions Analytics compared hybrids with their internal combustion engine equivalents. Using the company’s standardized on-road cycle, it determined the average CO2 reduction from hybridization was 23 percent for the EU and 34 percent for the US, with an average of 30 percent across all pairings.

Emissions Analytics then calculated the distance-specific CO2 reduction per unit of battery size (capacity), in g/km/kWh, for mild, full, plug-in hybrids, and BEVs. The results indicated that mild hybrids are the most efficient way to reduce CO2, given limited global battery capacity. With a reduction of 73.9g/km/kWh, the technology was a clear favorite, with full hybrids coming in second at 50.5g/km/kWh.

Due to their disproportionately large batteries, BEVs were the worst of the available options, with a mere 3.5g/km/kWh reduction. The size of BEV batteries tends to be large to accommodate infrequent, extreme use cases—like high-mileage trips, not often undertaken by average drivers—and do not make the best uses of limited supply.

The calculations did not take into account the upstream CO2 in fuel extraction, refining, and transportation, or the production and distribution of electricity. Some studies suggest the upstream CO2 of electricity is greater than for gasoline, but the relative efficiency calculations here implicitly assume they are equal.

While electrification has proved to be a promising path to reducing tailpipe emissions, the most extreme form of the technology—fully-electric vehicles—are found to be a highly inefficient way to achieve an urgent and meaningful emissions reduction. This is also hampered with supply chain issues and consumer acceptance challenges causing Emissions Analytics to find an alternative use of the world’s limited battery supply.

Improving the air quality in cities is another popular reason for those championing BEVs. It is, however, a false assertion that they are needed to fulfil this purpose. Existing technology is more than capable of bringing cities within compliance, the primary polluters being vehicles with older internal combustion engine technology.

Emissions Analytics proposes two possible solutions. One is a switch from gasoline to diesel, reducing CO2 by 11 percent, coupled with a mild hybrid system, providing a further six percent reduction. A final swap to full hybrids would deliver an addition 16 percent reduction for a 34 percent total. Alternatively, switching directly from gasoline to gasoline mild hybrids provides an 11 percent reduction, with a further 23 percent from the move to full hybrid.