Emissions from PHEVs vs. BEVs
Tailpipe Emissions:
- BEVs have zero tailpipe emissions at all times because they run entirely on electricity and do not use an internal combustion engine (ICE) at any point.
- PHEVs produce zero tailpipe emissions only when operating in all-electric mode; however, when their ICE is engaged (using gasoline), they emit tailpipe pollutants, including CO2.
- PHEVs can also produce evaporative emissions even when the engine is off because of the gasoline fuel system.
Real-World Emissions Performance:
- Studies have shown that PHEVs can emit significantly more CO2 in real-world driving conditions than official test ratings suggest, sometimes five to seven times more CO2 when the gasoline engine is running. This is partly because many PHEVs were originally designed as conventional ICE vehicles, with batteries added primarily to improve test cycle results.
Life Cycle Emissions (Cradle-to-Grave):
- Life cycle emissions consider not only tailpipe emissions but also upstream emissions from fuel production (electricity or gasoline), as well as emissions from manufacturing and disposal of the vehicle and battery.
- BEVs have no tailpipe emissions but their total emissions depend substantially on the electricity generation mix. In regions with clean electricity sources, BEVs have a large emissions advantage; in areas with high-emission electricity generation, the advantage diminishes but still typically remains.
- PHEVs’ life cycle emissions depend on how often they are driven in electric-only mode versus gasoline mode, and the carbon intensity of the electricity they use.
Comparative Life Cycle Emissions Insights:
- Contrary to common assumptions, some analyses suggest that PHEVs may produce lower lifetime greenhouse gas emissions than BEVs in the current U.S. context due to having much smaller batteries (approximately one-sixth the size of BEV batteries), thus lower emissions from battery production.
- Because PHEVs rely less on grid electricity and supplement with gasoline, their use phase emissions are higher than BEVs but lower than conventional vehicles.
- The smaller battery size in PHEVs means they have lower embodied carbon from battery manufacturing, which can lead to better overall climate performance, especially when the grid is still dominated by fossil fuels.
- BEVs gradually narrow the life cycle emissions gap as vehicle mileage increases and the electricity grid becomes cleaner, but within typical vehicle lifespans (around 125,000 miles), PHEVs often maintain a life cycle emissions advantage.
Summary Comparison
| Factor | Battery Electric Vehicles (BEVs) | Plug-in Hybrid Electric Vehicles (PHEVs) |
|---|---|---|
| Tailpipe Emissions | Zero at all times | Zero in electric mode; significant emissions when using gasoline |
| Real-world Emissions | Low, dependent on electricity mix | Higher than official ratings; substantial CO2 emitted when engine runs |
| Battery Size/Production Impact | Large battery, high embodied emissions | Smaller battery, lower embodied emissions |
| Life Cycle Emissions | Low where grid is clean; can be higher where grid remains fossil-fueled | Potentially lower due to smaller battery and hybrid operation, especially on current grids |
| Dependence on Electricity Grid | Fully dependent | Partial, supplemented by gasoline |
In conclusion, BEVs are unequivocally zero-emission at the tailpipe and can achieve very low life cycle emissions with clean electricity. However, PHEVs can sometimes outperform BEVs in overall life cycle greenhouse gas emissions because of their smaller batteries and flexibility in fuel use, especially in regions with carbon-intensive electricity generation or during the current grid transition period. Nevertheless, PHEVs do emit tailpipe pollutants when running on gasoline, making BEVs cleaner in use-phase emissions.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-do-plug-in-hybrid-electric-vehicles-phevs-compare-to-battery-electric-vehicles-bevs-in-terms-of-emissions/
