What is a hybrid car and how do they work?

What is a hybrid car and how do they work?

A hybrid car is powered by an electric motor and an internal combustion engine (ICE).

As hybrid cars are partially driven by their electric motors, they typically offer greater fuel efficiency and produce less emissions than pure ICE vehicles. Despite being partially or fully dependent on a combustion engine, hybrid cars are often classed as electric cars.

In this guide, we’ll explain what constitutes a hybrid car. We’ll also take a look at the history of hybrid cars, how they work – and the different types of hybrid cars on the market today. Finally, we’ll explore whether it’s worth buying a hybrid.

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What is a hybrid car?

For those unfamiliar, the word ‘hybrid’ originates from the Latin term ‘hybrida’, which refers to the offspring of a domestic pig and a wild boar. Today, ‘hybrid’ can refer to anything that comprises two different elements.

The term ‘hybrid car’ refers to a vehicle that is propelled partly by an electric motor and partly by a petrol or diesel combustion engine. It has been popularly used since 1997, when the Toyota Prius, the first hybrid to achieve mainstream success, arrived on the market in Japan.

The overwhelming majority of hybrid cars have petrol engines. Mercedes-Benz is currently the only major manufacturer that offers diesel hybrids. Therefore, in this article, we will use the term ‘hybrid’ to refer to petrol-electric hybrid cars.

How do hybrid cars work?

A hybrid car captures energy through a process called ‘regenerative braking’. Whenever the driver uses the brakes, the kinetic energy created is then used to power the electric motor. This reduces the reliance on the combustion engine, improves efficiency and reduces CO2 emissions.

Many modern HEVs and PHEVs allow you to select the strength of the regenerative braking force. These controls are usually built into the steering wheel. The optimal braking strength will depend on the type of road you’re driving on.

A weaker regenerative braking setting is ideal for motorways, as it will provide a smoother driving experience. However, a stronger setting can improve your car’s efficiency when driving through the city due to the stop/start nature of urban motoring.

Types of hybrid cars

There are three main types of hybrid cars on the market. In this section, we will clarify the differences in how they work.

HEVs/self-charging hybrids

HEVs (also known as ‘self-charging hybrids’) can’t be plugged into a home or public charger. Instead, the batteries are charged by the petrol engine, which acts as a generator – or by power recovered from braking, which is converted from kinetic to electric energy through the regenerative braking process.

HEVs can only run solely on electric power for very short distances (around a mile) and at lower speeds (up to around 25mph).

So, you probably wouldn’t be able to complete your morning commute (or the school run) without producing CO2 emissions. In a practical sense, a HEV’s electric motor exists to support the petrol engine.

Plug in hybrids (PHEVs)

Much like HEVs, plug-in hybrid electric vehicles (PHEVs) have an engine and an electric battery/motor combo. However, as the name suggests, PHEVs’ batteries can be charged using a socket. Due to their more sophisticated technology, PHEVs are typically priced higher than comparable HEV models.

A PHEV has more in common with a BEV than a HEV, as it can complete some journeys on electric power alone. PHEVs have larger batteries and more powerful electric motors than HEVs, allowing them to travel solely on electric power for longer distances (20-80+ miles) and at higher speeds (70mph or more).

PHEVs are often used as company cars. Due to their lower CO2 emissions, PHEV company car drivers typically pay low rates of Benefit-in-Kind (BIK) tax than PHEV or ICE car drivers.

Mild hybrids (MHEVs)

Mild hybrid electric vehicles (MHEVs) cannot be classed as hybrids in a conventional sense. Whilst they do have (very small) electric motors and batteries, MHEVs cannot run solely on electric power.

Instead, the small battery and motor can assist the engine whilst the car moves from stationary. The engine also switches off when the car is coasting downhill, whilst the electric battery keeps crucial systems such as the power steering running.

In a sense, MHEV technology is more of a sophisticated start/stop system than it is a hybrid powertrain.

MHEVs are generally cheaper than both HEV and PHEVs. Despite lacking some of the benefits associated with hybrids, they’re still more economical to run than many ICE models. Modern mild hybrids will also qualify for exemption from most emission zone charges in the UK.

Pros and cons of hybrid cars

In this section, we’ll list the key benefits and drawbacks of different hybrid car types to help you decide which option best suits your needs and budget:

HEVs/self-charging hybrids


  • Favourable fuel economy compared to ICE and MHEV cars.

  • Zero-emission driving is possible for short distances at low speeds.

  • HEVs tend to deliver a smooth driving experience.

  • No need to plug in to charge.

  • Cheaper than PHEVs.

  • May be a good option for drivers without home charging and poor access to public charge points.


  • Mostly reliant on a petrol or diesel engine.

  • Zero-emission driving is not possible for full journeys and is limited to low speeds.

  • Less favourable BIK tax rates than PHEVs and BEVs

  • Some drivers feel that a HEV provides a less engaging experience.



  • Zero-emission commutes are possible for many drivers, providing the battery is topped up.

  • Zero-emission driving is possible at all legal speeds.

  • Good performance and driving economy.

  • Favourable road tax and BIK tax rates.

  • PHEVs are lighter than BEVs (due to having smaller batteries) but still offer many of the same benefits.


  • Fuel economy can be poor if the battery is not topped up on a regular basis.

  • Expensive compared to HEVs, MHEVs and ICE cars.

  • Some uncertainty over resale value with the impending 2035 ICE ban.

  • Repairs and maintenance can be expensive.

Are hybrid cars worth it?

When deciding whether a hybrid car is worth your money, it’s important to factor in your budget, preferences and driving habits:

  • If you regularly make short journeys in town, either a PHEV or a HEV could provide a smooth and economical driving experience.
  • PHEVs are better suited to motorway commutes.
  • Upfront costs for hybrids are typically higher than ICE cars, but you can still find many great used hybrids at affordable prices.
  • If your mileage is very high (e.g. 40,000+ per year), you may be better off with a diesel due to their longevity.
  • If you’ve been offered a company car, consider a PHEV or a BEV, due to the lower BIK and road tax rates.
  • All hybrid and fully electric cars have automatic gearboxes, providing a simple, hassle-free driving experience.
  • PHEVs are on the expensive side and if you can afford one, you should also examine whether a BEV would better suit your driving needs.
  • Although range anxiety has deterred many prospective BEV drivers in the past, most modern BEVs have ranges of 200-300 miles. The Mercedes EQS has a range of 452 – the longest available on the UK market.

The evolution of hybrid vehicles

Early years (1899-1920)

  • The very first hybrid car, dubbed the ‘System Lohner-Porsche Mixte’ was built in 1899 by the engineer Ferdinand Porsche. The Mixte utilised a gasoline engine, which supplied power to an electric motor that drove the front wheels.
  • The Mixte was relatively successful – and more than 300 units were produced.
  • However, around 1904, when Henry Ford began mass producing solely petrol-powered cars at low prices, interest in hybrid motoring began to decline.
  • Hybrids based on the Mixte were produced into the 1910s, but they sold poorly compared to more powerful pure petrol models, whilst also costing more.
  • As a result, hybrid motoring faded into obscurity for almost 50 years.

New attempts to revive hybrid motoring (1960-1996)

  • In the 1960s, the United States Congress introduced new legislation to tackle air pollution and encourage more widespread adoption of electric vehicles.
  • Whilst the US Government tried to gain support for hybrids, public interest remained low.
  • However, this changed in 1973 when the Arab oil embargo drastically reduced the availability of gasoline and drove up prices.
  • Over the following years, automotive manufacturers spent billions of dollars researching and developing new hybrid technologies, although many struggled to produce low-emission cars that could compete with their ICE rivals on price and performance.

The age of the modern hybrid car (1997-present)

  • A small number of fully electric Battery Electric Vehicles (BEVs) were introduced in the late 1990s, including the Toyota RAV 4 EV – and the GM EV 1. However, these early entrants to the electric car market failed to generate much interest and were soon dropped from production.
  • However, it was Toyota’s flagship hybrid, the Prius that ushered in the age of the modern hybrid car when it launched in Japan in 1997.
  • The first-generation Prius was the world’s first mass-produced hybrid electric vehicle (HEV). Between December 1997 and February 2000, a total of 37,425 units were produced at the Takaoka plant in Toyota, Aichi.
  • The Prius won two coveted awards in Japan: the 1997 Car of the Year Award – and the 1998 Automotive Researchers’ and Journalists’ Conference Car of the Year Award.
  • In 1999, the Honda Insight became the first HEV to reach the US market.
  • However, it was ultimately the first Toyota Prius sedan, which arrived in the US the following year, that helped to make HEVs a permanent fixture on the global automotive market.
  • Ever since its US launch, the Prius has become synonymous with the word ‘hybrid’ - and is to date the most popular HEV ever produced.
  • Numerous automakers around the world have since used its technology as a basis for their own HEV offerings.

The future of hybrid cars

  • Growing numbers of automakers are now offering hybrid versions of their most popular models. Some of the best-selling models on the UK market include the Kia Sportage, Honda Civic, Kia Niro Hybrid and the Renault Clio.
  • All types of electric cars, including HEVs, Plug in Hybrids (PHEVs) and BEVs all now have larger market shares than diesel powertrain cars in the UK.
  • According to the latest data from the Society of Motor Manufacturers and Traders (SMMT) in February 2024, BEVs had the largest market share of all electric car types (17.7%), followed by HEVs (12.7%) and PHEVs (7.2%).
  • Today, hybrid drivers in the UK can enjoy favourable road tax rates – and exemption from many emissions-based zone charges, including the Ultra Low Emission Zone (ULEZ) in London and the Clean Air Zone (CAZ) in other various cities.
  • London’s congestion charge now applies to all hybrid cars. Whilst some PHEVs were once exempt from the charge, only BEVs are now exempt.
  • Some see hybrid powertrains as a transitional technology. From 2035, the sale of new ICE vehicles, including hybrids (which incorporate combustion engines) will be banned in the UK. This legislation will not prevent used hybrids from being bought and sold.