The journey towards accurate emissions reporting for Plug-in Hybrid Electric Vehicles (PHEVs) challenges conventional methodologies with its unique blend of fuel and electricity consumption. At Scopes Data, we delve deep into the intricacies of PHEV operations, acknowledging that standard NEDC and WLTP assumptions do not fully capture their environmental footprint. Our dedicated process for assessing electricity efficiency alongside fuel consumption is designed to unveil the true CO2 emissions of PHEVs, ensuring your fleet's sustainability metrics are as precise and reliable as possible.
Balancing Fuel and Electricity Consumption
Traditional testing frameworks often apply a generic 70% electricity and 30% fuel use ratio for PHEVs, a simplification that overlooks real-world variability. Scopes Data adopts this ratio as a starting point but goes further to refine emissions estimates by closely analyzing vehicle-specific data on fuel and electricity usage, ensuring a more accurate reflection of each vehicle's environmental impact.
Fuel Consumption
For the combustion component of PHEVs, we calculate CO2 emissions by integrating the fuel emission factor with the actual proportion of fuel used. This method acknowledges the diversity in fuel consumption patterns among PHEVs, influenced by factors such as driving behavior and operational conditions.
Electricity Consumption
When assessing the electric side of PHEVs, our analysis extends beyond mere availability of electricity efficiency data. We generate electricity efficiency figures based on battery capacity and driving range, then combine these with the emission factors (EF) specific to each country—or states within countries, such as the US—to calculate the CO2 emissions attributable to electricity use. This level of detail ensures that our emissions reporting accurately reflects the impact of electrical energy consumption on the environment.
Delving Deeper into the Real-World Performance of PHEVs under WLTP Standards
Development of the average real-world and type-approval fuel consumption of private and company car PHEVs in Europe over vehicle build year. Shaded areas represent 95% confidence interval from sample size uncertainty[Ref. 1].
The Worldwide Harmonized Light Vehicles Test Procedure (WLTP) sets the standard for vehicle fuel consumption and emissions testing. Although it was believed that the WLTP would present a more accurate depiction of Plug-in Hybrid Electric Vehicles (PHEVs) performance, recent evidence suggests notable deviations between real-world and type-approval results.
A study analyzed the performance of approximately 9,000 PHEVs in Europe, focusing on those certified under WLTP. Findings revealed that real-world fuel consumption for these vehicles was significantly higher than WLTP type-approval values, with private vehicles consuming an average of 4.0–4.4 L/100 km and company cars even higher at 7.6–8.4 L/100 km. This is in stark contrast to the projected 1.6–1.7 L/100 km by WLTP. Furthermore, actual CO2 emissions were much higher than the type-approval values, especially for company cars.
Interestingly, the disparity between real-world and type-approval values has been increasing yearly since 2012. Newer WLTP-certified cars showed even higher real-world fuel consumption than their predecessors.
The electric driving share, which measures the distance driven using only the electric motor, also deviated from expectations. Real-world data displayed an electric driving share of 45%–49% for private cars and 11%–15% for company cars, whereas WLTP assumed figures between 70% and 85%.
These deviations underscore the need for an overhaul of the WLTP assumptions to more accurately mirror real-world PHEV usage.
