Hybrid Electric Vehicles

• 10 Mar 2026

Source: IE 

Why in News? 

Delhi's upcoming Electric Vehicle (HEV) policy plans to extend road tax and registration fee exemptions, currently available for battery electric vehicles (BEVs), to hybrid electric vehicles (HEVs) as well. 

What are Hybrid Electric Vehicles?  

• About: A Hybrid Electric Vehicle (HEV) is an automobile that combines a conventional internal combustion engine (ICE) with an electric propulsion system to achieve better fuel efficiency and lower emissions, operating without the need for external charging. 
  • It seamlessly switches between or combines these power sources to optimize efficiency, leveraging the engine for extra range, and the motor for instant acceleration and noise-free driving. 
• Self-Charging Capability: Unlike pure electric vehicles (EVs), a standard hybrid's battery is self-charging. It does not need to be plugged in; it is replenished automatically through regenerative braking and, in some designs, by the gasoline engine acting as a generator. 
  • During braking, the electric motor acts as a generator, converting the vehicle's kinetic energy (which would otherwise be lost as heat) into electricity to recharge the battery.  
• Types of Hybrid Configurations: 
  • Parallel Hybrid: Both the engine and the electric motor are mechanically connected to the wheels, allowing them to power the vehicle either independently or simultaneously. While some short electric-only driving is possible, the motor typically acts as an assist to the engine. 
  • Series-Parallel (Power-Split) Hybrid: It can intelligently switch between modes—running on electric power alone, using the engine to generate electricity for the motor (series mode), or having both power sources drive the wheels directly (parallel mode). 
  • Plug-in Hybrid Electric Vehicle (PHEV): Its defining characteristic is the ability to be recharged externally via a plug, in addition to being charged by the engine and regenerative braking. PHEVs can use any hybrid architecture (parallel, series, or series-parallel) and offer the dual benefit of electric commuting and unlimited hybrid range for longer trips. 
• Advantages: Hybrids deliver excellent fuel economy—especially in city driving—and lower emissions through features like regenerative braking, while eliminating the range anxiety associated with pure electric vehicles. Additional benefits include reduced brake wear and, depending on the type and location, potential eligibility for government incentives such as tax credits. 
• Disadvantages: Hybrids carry a higher initial cost than conventional cars due to their complex technology, and some drivers find them less engaging to drive. Additional drawbacks are high battery replacement, and the fuel economy advantage is most pronounced in city driving rather than on the highway. 

Other Possible Alternative Technologies to HEVs 

• Battery Electric Vehicles (BEVs): These vehicles are powered solely by large rechargeable batteries and electric motors, producing zero tailpipe emissions. They depend entirely on external charging infrastructure and face range limitations based on battery capacity. 
• Fuel Cell Electric Vehicles (FCEVs): These vehicles use hydrogen fuel cells to generate electricity on board, powering an electric motor with water vapor as the only byproduct.  
• Hydraulic Hybrids: These systems capture braking energy in hydraulic accumulators using fluid pressure, rather than storing it in batteries, to assist with propulsion. 
• Conventional Vehicles with Alternative Fuels: This category includes vehicles that retain internal combustion engines but run on non-petroleum fuels, such as flex-fuel vehicles (compatible with ethanol blends like E85), Compressed Natural Gas (CNG), or biofuels, offering emission reductions without electrification. 

Frequently Asked Questions (FAQs) 

1. What is a Hybrid Electric Vehicle (HEV)? 
An HEV combines an internal combustion engine (ICE) with an electric motor and battery to improve fuel efficiency and reduce emissions, typically without requiring external charging. 

2. How does regenerative braking work in hybrid vehicles? 
During braking, the electric motor acts as a generator, converting kinetic energy into electricity and storing it in the battery. 

3. How are Battery Electric Vehicles (BEVs) different from hybrids? 
BEVs run entirely on electric batteries with zero tailpipe emissions, while hybrids combine electric propulsion with an internal combustion engine. 

UPSC Civil Services Examination, Previous Year Questions (PYQs)  

Q. With reference to green hydrogen, consider the following statements : (2023)

1. It can be used directly as a fuel for internal combustion.  
2. It can be blended with natural gas and used as fuel for heat or power generation.  
3. It can be used in the hydrogen fuel cell to run vehicles.  

How many of the above statements are correct?  

(a) Only one  

(b) Only two  

(c) All three  

(d) None 

Ans: (c)

Q. In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index? (2016)

1. Carbon dioxide 
2. Carbon monoxide 
3. Nitrogen dioxide 
4. Sulfur dioxide 
5. Methane 

Select the correct answer using the code given below: 

(a) 1, 2 and 3 only 

(b) 2, 3 and 4 only 

(c) 1, 4 and 5 only 

(d) 1, 2, 3, 4 and 5 

Ans: (b)

Q. Hydrogen fuel cell vehicles produce one of the following as “exhaust” (2010)

(a) NH₃  

(b) CH₄  

(c) H₂O  

(d) H₂O₂ 

Ans: (c)