Impact on PHEVs and HEVs Fuel Efficiency
- Variation from Official Ratings: PHEVs often show substantially lower fuel efficiency in real-world driving compared to official fuel economy ratings. For example, consumer group testing found that PHEVs were on average 61% less fuel-efficient in real driving conditions than the official lab-based fuel ratings suggested.
- System Power and Energy Consumption: Real-world fuel consumption and CO2 emissions for PHEVs decrease by approximately 2%–4% with every additional 10 kW of system power taken from the vehicle’s hybrid system. This suggests that more powerful electric systems can improve efficiency under real-use conditions.
- Dependence on Ambient Temperature and Driving Mode: Studies show energy consumption for PHEVs varies strongly with ambient temperature and the mix of driving modes (electric vs. internal combustion engine). For example, energy use ranged between 233 to 1170 Wh/km in combustion engine mode, but only 135 to 420 Wh/km in electric motor mode. Average consumption was about 894 Wh/km for the combustion engine and 208 Wh/km for the electric motor under real driving conditions.
- Battery Charge State and Driving Patterns: PHEVs that are not regularly charged tend to rely more on their internal combustion engines, resulting in higher fuel consumption and emissions. Additionally, real-world driving scenarios—such as stop-and-go traffic, highway speeds, and ambient conditions—affect how much the electric motor versus the combustion engine is used, influencing fuel efficiency.
- Weight Penalty: PHEVs generally have higher curb weights due to larger batteries compared to standard HEVs or conventional vehicles, which negatively impacts fuel consumption if the battery is not charged or used optimally.
- Emission Reductions in Real Conditions: Despite these challenges, PHEVs tested on-road have shown to emit regulated pollutants well below Euro 6d limits and even have reductions in greenhouse gases when operated in charge-sustaining modes compared to conventional gasoline vehicles.
Summary
Real-world driving conditions such as ambient temperature, driving style, charging frequency, and vehicle load cause fuel efficiency of HEVs and PHEVs to deviate from laboratory estimates. PHEVs tend to be less fuel-efficient in real-world conditions if the electric motor is underutilized (e.g., insufficient charging), partly due to their additional weight and reliance on the combustion engine. However, when driven in a way that maximizes electric use and charged regularly, they achieve significant energy savings and emissions reductions. The efficiency of HEVs and PHEVs in actual driving conditions is therefore highly dependent on user behavior and environmental factors.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-do-real-world-driving-conditions-affect-the-fuel-efficiency-of-hevs-and-phevs/
