A common topic in the news these days is the “eco-car,” an environmentally friendly automobile featuring high fuel efficiency and low-impact emissions. One of the more promising categories of the eco-car is the hybrid, an automobile equipped with two or more types of power sources, typically a gasoline engine and an electric motor. Although still relatively unknown in Europe, hybrid cars are carving out niches in the Japanese and U.S. auto markets as next-generation eco-cars.

When an ordinary gasoline-powered car brakes, the dissipated is lost. In a hybrid car, however, some of this energy is saved as electrical power and used to recharge the battery. Since the battery is charged while the car is running, there is no need to recharge it from an external power source, unlike a purely electric car. The electrical power saved in the battery is used when the car starts up and accelerates, thereby economizing on the use of gasoline. The energy savings are especially great in stop-and-go city driving, where drivers do most of their braking and accelerating.

Toyota Motor Corp. came out with the world’s first mass-produced hybrid passenger vehicle, the Prius, in 1997. Its fuel efficiency was double that of existing gasoline-powered cars. What’s more, it emitted only one-half the volume of carbon dioxide and just one-tenth the volume of nitrogen oxides emitted by conventional cars. Toyota followed with a hybrid minivan, the four-wheel drive Estima Hybrid, in 2001. In July 2003 it came out with another minivan, the Alphard Hybrid, and in September 2003 it introduced a new version of the Prius. Meanwhile, Honda Motor Co. used its own hybrid-car technology to launch the Insight in the autumn of 1999 and the Civic Hybrid in November 2001.

Hybrid cars can be divided into three broad categories according to their power system. The series hybrid system uses a gasoline engine to run a generator and an electric motor to drive the wheels. The parallel hybrid system uses both a gasoline engine and an electric motor to power the wheels, switching between them depending on the situation. And the Toyota Hybrid System, or THS, is a compound of the series and parallel systems, drawing on the strong points of both. THS uses a “power-split device,” which adjusts power generation and drive-power distribution between the gasoline and electric engines for maximum efficiency. Since the system supplies energy to drive the electric motor, it uses the motor to a greater degree than a series hybrid car.

The new Prius is a two-wheel-drive five-seater with a 1.5-liter engine, selling for JPY2.15 million–JPY2.57 million (US$20,000–US$24,000). It is a completely redesigned version of the inaugural Prius, which sold more than 120,000 units. Equipped with the THS II, the next-generation Toyota Hybrid System, the new Prius offers one of the world’s highest levels of fuel efficiency, averaging 35.5 kilometers per liter of gasoline, or 83.5 miles per gallon. It also boasts one of the world’s lowest levels of emissions for a vehicle of its size. And it produces 50% better output than the original THS by using a higher voltage (maximum 500 volts), which has dramatically improved performance.

The new Prius also comes with advanced electronic controls, including the world’s first Intelligent Parking Assist system, which guides steering in curbside parking and similar situations, and an electric vehicle drive mode, which allows the car to be driven on the electric motor alone. Priced relatively inexpensively considering its advanced features and performance, the new Prius sold about 17,500 units in its first month.

Honda’s hybrid cars use a system, called Integrated Motor Assist, that relies constantly on the gasoline engine for power, but with the electric motor providing additional power during startup and acceleration. For ordinary cruising, the engine alone powers the car. The motor, measuring just 60 millimeters in width, connects directly to the engine crankshaft for efficient power-delivery and regeneration. For power storage, it uses a 44-volt nickel metal hydride battery, weighing in at about 20 kilograms.

Honda offers two hybrid models. The five-seat Civic Hybrid has a displacement of 1.34 liters and sells for JPY2.12 million (US$19,626), and the two-seat Insight has a 1.0-liter displacement and sells for JPY2.10 million–JPY2.18 million (aboutUS$20,000). The models average 29.5 kilometers and 35 kilometers to the liter (69 miles and 82 miles per gallon), respectively.

In Japan, where gasoline can be quite expensive—as much as twice that in the United States, for example—fuel efficiency is an important consideration. If the prices of hybrids come down a bit further, they have good prospects of winning acceptance as ordinary cars for the mass market.

Another factor favoring hybrid cars is tax breaks offered by the government: New cars that meet fuel efficiency standards set for 2010 and are certified as low-emission vehicles earn a reduction of JPY15,000 (US$140) in the automobile acquisition tax and about 50 percent of the automobile tax payable in the first year thereafter.

Similar trends in high gas prices, tough emission controls and tax breaks could create promising exports markets for Japanese hybrids in other countries as well.

Turning to the future, one of the biggest hopes is for the development of hybrids in less efficient classes of vehicles, such as sport-utility vehicles (SUVs). It is also hoped that hybrid technology can be applied to Japanese fuel-cell cars, the ultimate eco-cars, which promise exceptionally low-impact operation.