A Petroleum Electric Hybrid Vehicle (PEHV) is a vehicle using an on-board rechargeable energy storage system (RESS) and a fueled power source for vehicle propulsion. The HV pollutes less and uses less fuel during its useful life. The different propulsion power systems may have common subsystems or components. The HV provides better fuel economy than a conventional vehicle because the engine is smaller and may be run at speeds providing more efficiency. Other techniques may be used to recover or reduce waste energy (such as regenerative braking and shutting down the combustion engine).

PHEVs most commonly use internal combustion engines and electric batteries to power electric motors. Modern mass-produced hybrids prolong the charge on their batteries by capturing kinetic energy via regenerative braking. As well, when cruising or in other situations where just light thrust is needed, "full" hybrids can use the combustion engine to generate electricity by spinning an electrical generator (often a second electric motor^[1]) to either recharge the battery or directly feed power to an electric motor that drives the vehicle. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrids still require gasoline and diesel as their sole fuel source though other fuels such as ethanol or plant based oils have also seen occasional use.

The term hybrid when used in relation with cars also has other uses. Prior to its modern meaning of hybrid propulsion, the word hybrid was used in the United States to mean a vehicle of mixed national origin; generally, a European car fitted with American mechanical components. This meaning has fallen out of use. In the import scene, hybrid was often used to describe an engine swap. Some have also referred to flexible-fuel vehicles as hybrids because they can use a mixture of different fuels — typically gasoline and ethanol alcohol fuel.

Contents 1 History 2 Hybrids currently available 2.1 Automobiles and light trucks 2.2 Trains, trucks and buses 2.3 Locomotives 2.4 Other military vehicles 2.5 Taxicabs 3 Types 4 Engines and fuel sources 4.1 Gasoline 4.2 Diesel 5 Benefits 5.1 Incentives 5.1.1 United States 5.1.2 Canada 5.1.3 United Kingdom 5.2 Trade-offs 6 Hybrids vs. electric vehicles 6.1 Plug in 7 See also 8 External links 8.1 General 8.2 Hybrid powertrains 8.3 Hybrids in logistics 8.4 Hybrids in public transport 9 References

 

History

In 1898 Ferdinand Porsche designed the Lohner-Porsche carriage, a series-hybrid vehicle that broke several Austrian speed records, and also won the Exelberg Rally in 1901 with Porsche himself driving. Over 300 of the Lohner-Porsche carriages were sold to the public. However this is more an example of electrical transmission than a hybrid vehicle.

The 1915 Dual Power made by the Woods Motor Vehicle electric car maker had a four cylinder internal combustion engine and an electric motor. Below 15 mph (25 km/h) the electric motor alone drove the vehicle and above this speed the "main" engine cut in to take the car up to its 35 mph (55 km/h) top speed. About 600 were made up to 1918. ^[2]

There have also been air engine hybrids where a small petrol engine powered a compressor. Several types of air engines also increased the range between fill-ups with up to 60% by absorbing ambient heat from its surroundings.^[3]

In 1959 the development of the first transistor-based electric car—the Henney Kilowatt—heralded the development of the electronic speed control that paved the way for modern hybrid electric cars. The Henney Kilowatt was the first modern production electric vehicle and was developed by a cooperative effort between National Union Electric Company, Henney Coachworks, Renault, and the Eureka Williams Company. Although sales of the Kilowatt were dismal, the development of the Kilowatt served was a historical "who's who" of electric propulsion technology.

A more recent working prototype of the electric-hybrid vehicle was built by Victor Wouk (one of the scientists involved with the Henney Kilowatt and also brother of author Herman Wouk ). Wouk's work with electric hybrid vehicles in the 1960s and 1970s earned him the title as the "Godfather of the Hybrid"^[4]). Wouk installed a prototype electric-hybrid drivetrain into a 1972 Buick Skylark provided by GM for the 1970 Federal Clean Car Incentive Program, but the program was killed by the EPA in 1976 while Eric Stork, the head of the EPA at the time, was accused of a prejudicial coverup^[5]. Since then, hobbyists have continued to build hybrids but none was put into mass production by a major manufacturer until the waning years of the twentieth century.

The regenerative-braking hybrid, the core design concept of most production hybrids, was developed by Electrical Engineer David Arthurs around 1978 using off-the shelf components and an Opel GT. However the voltage controller to link the batteries, motor (a jet-engine starter motor), and DC generator was Mr. Arthurs'. The vehicle exhibited ~75 mpg fuel efficiency and plans for it (as well as somewhat updated versions) are still available through the Mother Earth News web site. The Mother Earth News' own 1980 version claimed nearly 84 mpg.

The Bill Clinton administration initiated the Partnership for a New Generation of Vehicles (PNGV)^[6] program in September 29, 1993 that involved Chrysler, Ford, General Motors, USCAR, the DoE, and other various governmental agencies to engineer the next efficient and clean vehicle. The NRC cited automakers’ moves to produce hybrid electric vehicles as evidence that technologies developed under PNGV were being rapidly adopted on production lines, as called for under Goal 2. Based on information received from automakers, NRC reviewers questioned whether the “Big Three” would be able to move from the concept phase to cost effective, pre-production prototype vehicles by 2004, as set out in Goal 3.^[7]

The program was replaced by the hydrogen focused FreedomCAR initiative^[8] of George W. Bush's administration in 2001. The focus of the FreedomCAR initiative being to fund research too high risk for the private sector to engage in with the long term goal of developing emission / petroleum free vehicles.

In the intervening period, the widest use of hybrid technology was actually in diesel-electric locomotives. It is also used in diesel-electric submarines, which operate in essentially the same manner as hybrid electric cars. However, in this case the goal was to allow operation underwater without consuming large amounts of oxygen, rather than economizing on fuel. Since then, many submarines have moved to nuclear power, which can operate underwater indefinitely, though a number of nations continue to rely on diesel-electric fleets.

Automotive hybrid technology became successful in the 1990s when the Honda Insight and Toyota Prius became available. These vehicles have a direct linkage from the internal combustion engine to the driven wheels, so the engine can provide acceleration power. The 2000s saw development of plug-in hybrid electric vehicles (PHEVs), which can be recharged from the electrical power grid and do not require conventional fuel for short trips. The Renault Kangoo was the first production model of this design, released in France in 2003. However, the environmental benefits of plug-in hybrids depend somewhat on the source of the electrical power. In particular, electricity generated with wind would be cleaner than electricity generated with coal, the most polluting source. On the other hand, electricity generated with coal in a central power plant is still much cleaner than pure gasoline propulsion, due to the much greater efficiencies of a central plant. Furthermore, coal is only one source of centrally generated power, and in some places such as California is only a minor contributor, overshadowed by natural gas and other cleaner sources.

The Prius has been in high demand since its introduction. Newer designs have more conventional appearance and are less expensive, often appearing and performing identically to their non-hybrid counterparts while delivering 50% better fuel efficiency. The Honda Civic Hybrid appears identical to the non-hybrid version, for instance, but delivers about 50 US mpg (4.7 L/100km). The redesigned 2004 Toyota Prius improved passenger room, cargo area, and power output, while increasing energy efficiency and reducing emissions. The Honda Insight, while not matching the demand of the Prius, is still being produced and has a devoted base of owners. Honda has also released a hybrid version of the Accord.

2005 saw the first hybrid sport utility vehicle (SUV) released, Ford Motor Company's Ford Escape Hybrid. Toyota and Ford entered into a licensing agreement in March 2004 allowing Ford to use 20 patents from Toyota related to hybrid technology, although Ford's engine was independently designed and built. In exchange for the hybrid licences, Ford licensed patents involving their European diesel engines to Toyota. Toyota announced model year 2005 hybrid versions of the Toyota Highlander and Lexus RX 400h with 4WD-i which uses a rear electric motor to power the rear wheels negating the need for a differential. Toyota also plans to add hybrid drivetrains to every model it sells in the coming decade.

For 2007 Lexus offers a hybrid version of their GS sport sedan dubbed the GS450h with "well in excess of 300hp". The 2007 Camry Hybrid becomes available starting Summer 2006 in USA and Canada. The initial batch of Camry Hybrids are built in Japan; starting October 2006, Toyota Motor Manufacturing, Kentucky (TMMK) will also produce these hybrids. Also, Nissan announced the release of the Altima hybrid (technology supplied by Toyota) around 2007.

An R.L. Polk survey of 2003 model year cars showed that hybrid car registrations in the United States rose to 43,435 cars, a 25.8% increase from 2002 numbers. California, the nation's most populous state at one-eighth of the total population, had the most hybrid cars registered: 11,425. The proportionally high number may be partially due to the state's higher gasoline prices and stricter emissions rules, which hybrids generally have little trouble passing.

Honda, which offers Insight, Civic and Accord hybrids, sold 26,773 hybrids in the first 11 months of 2004. Toyota has sold a cumulative 306,862 hybrids between 1997 and November 2004, and Honda has sold a total of 81,867 hybrids between 1999 and November 2004.^[9]

 Hybrids currently available

Main article: List of hybrid vehicles

See also: Upcoming Hybrid vehicles

 Automobiles and light trucks

A number of manufacturers currently produce hybrid automobiles and light trucks, including Ford, General Motors, Honda, Mazda, Nissan, Peugeot, Renault and Toyota. For a more complete list, see Production hybrid vehicles (organized by manufacturer).

Trains, trucks and buses

Main article: Hybrid Locomotive

In May 2003 JR East started test runs with the so called NE (new energy) train and validated the system's operability (series hybrid with lithium ion battery) in cold regions. In 2004, RailPower Technologies had been running pilots in the US with the so called Green Goats which led to orders by the Union Pacific and Canadian Pacific Railways starting in early 2005[1],[2],[3].

Also in 2005 GE introduced its hybrid shifters on the market. Toyota claims to have started with the Coaster Hybrid Bus in 1997 on the Japanese market. In May 2003 GM started to tour with hybrid buses developed together with Allison. Several hundreds of those buses have entered into daily operation in the US. The Blue Ribbon City Hybrid bus was presented by Hino, a Toyota affiliate, in January 2005.

In 2003 GM introduced a diesel hybrid military (light) truck, equipped with a diesel electric and a fuel cell auxiliary power unit. Hybrid light trucks were introduced 2004 by Mercedes (Hybrid Sprinter) and Micro-Vett SPA (Daily Bimodale). International Truck and Engine Corp. and Eaton Corp. have been selected to manufacture diesel-electric hybrid trucks for a US pilot program serving the utility industry in 2004. In mid 2005 Isuzu introduced the Elf Diesel Hybrid Truck on the Japanese Market. They claim that approximately 300 vehicles, mostly route buses are using Hinos HIMR (Hybrid Inverter Controlled Motor & Retarder) system.

New Flyer and Gillig produce hybrid buses using either ISE Corporation ThunderVolt or Allison's electric drive system. The Whispering Wheel bus is another hybrid.

A promising but as-yet unseen application for hybrid vehicle technology would be in garbage trucks, since these vehicles do stop-start driving and often stand idling.

 Locomotives

Main article: Hybrid Locomotive

Railpower^[10] offers hybrid road switchers, as does GE.^[11] Diesel-electric locomotives may not always be considered hybrids, not having energy storage on board, unless they are fed with electricity via a collector for short distances (for example, in tunnels with emission limits), in which case they are better classified as dual-mode vehicles.

Other military vehicles

The United States Army's manned ground vehicles of the Future Combat System all use a hybrid electric drive consisting of a diesel engine to generate electrical power for mobility and all other vehicle subsystems.

Taxicabs

Hybrid technology may be particularly appropriate for use as taxicabs, as in many locations they are used in predominantly urban environments; have intensive operating schedules, maximizing fuel savings over the life of the vehicle; and may spend considerable periods of time at idle, where the hybrid engine may allow for the combustion engine to be shut off (while retaining use of electrical accessories). Hybrid taxicabs are primarily based on production passenger vehicles, with modifications (often aftermarket) to meet specialized usage requirements and/or local regulations (security features, for example). Since vehicles in taxicab service may operate for 10-20 hours per day, the reduction in local pollution and noxious emissions may be more significant than that achieved by hybrids in private vehicle use.

In 2005, New York City added six Ford Escape Hybrids to their taxi fleet and city officials said the entire fleet of 13,000 vehicles could be converted within five years.^[12]

Types

Main article: Types of hybrid vehicle

There are many ways to create an electric-internal combustion hybrid. The variety of electric-ICE designs can be differentiated by the structure of the powertrain, the degree of hybridization and the mode of operation. The main categories are series hybrids and parallel hybrids, with combined hybrids having common characteristics of series and parallel designs.

Hybrids other than electric-internal combustion exist, for example hydraulic and pneumatic hybrids, where compressed fluids and compressed air, respectively, are used for energy storage with regenerative braking.

 Engines and fuel sources

 Gasoline

Gasoline engines are used in most hybrid designs, and will likely remain dominant for the foreseeable future. While petroleum-derived gasoline is the primary fuel, it is possible to mix in varying levels of ethanol created from renewable energy sources. Like most modern ICE-powered vehicles, hybrids can typically use up to about 15% bioethanol. Manufacturers may move to flexible fuel engines, which would increase allowable ratios, but no plans are in place at present.

Nowadays petroleum gasoline engines can use directly biobutanol (see direct biofuel).

 Diesel

One potentially interesting hybrid vehicle combination uses a diesel engine for power generation. Diesels have advantages when delivering constant power for long periods of time, suffering less wear while operating at higher efficiency. The Diesel engine's high torque, combined with hybrid technology, may offer performance in a car of over 100 mpg US (2.35 litres/100 km). Most diesel vehicles can use 100% pure biofuels (biodiesel), so they can use but do not need petroleum at all; if diesel-electric hybrids were in use, this benefit would likely also apply.

Diesel-electric hybrids with parallel drivetrains like the Prius may have a substantial cost disadvantage to other options. Diesel engines are generally more expensive than gasoline equivalents, due to the demands for higher compression (although this also makes diesels more durable). If this "diesel premium" is added to any additional expense for the hybrid, the diesel-electric combination may make the payback period for such vehicles even longer and less feasible for many consumers. In addition, the higher torque of diesel engines may obviate one of the advantages of the electric motors. As with regular diesel engines, diesel-electric hybrids may be more appropriate for high-mileage, intensive-use applications, such as buses, trucks, and delivery vehicles, and less appropriate for passenger vehicles. In addition, regular diesel vehicles may get similar mileage to gasoline-electric hybrids, for a smaller premium, and the marginal benefit of "hybridization" may not be viable.

Diesels are not widely used for passenger cars in the United States, as US diesel fuel has long been considered very "dirty", with relatively high levels of sulfur and other contaminants in comparison to the Eurodiesel fuel in Europe, where greater restrictions have been in place for many years. Despite the dirtier fuel at the pump, the US has tough restrictions on exhaust, and it has been difficult for car manufacturers to meet emissions levels as higher sulfur levels are damaging to catalytic converters and other emission control systems. However, ultra-low sulfur diesel was mandated and became widely available in the U.S. in October 2006 for highway vehicles, which will allow the use of newer emissions control systems.

Diesel-electric motors are common for use as locomotives, but using a serial hybrid design. In locomotives, the diesel engine is used to generate electricity for the electric drivetrain. This configuration allows the internal combustion engine to be operated at more efficient operating parameters, while removing the need for a separate transmission for the ICE unit and allowing the efficient delivery of torque from the electric motors. Such a system may need a smaller diesel engine and allow for better emissions controls, since the operating range of the diesel engine would be optimized for electric generation rather than power delivery through the mechanical transmission and wheels. There have been studies of this type of diesel-electric hybrid, but there are no confirmed attempts to commercialize such a vehicle for passenger use.

PSA Peugeot Citroën has unveiled two demonstrator vehicles featuring a diesel-electric hybrid powertrain: the Peugeot 307 and Citroën C4 Hybride HDi (PDF). VW made a prototype diesel-electric hybrid car that achieved 2 litres/100 km (118 mpg US) fuel economy, but has yet to sell a hybrid vehicle. General Motors has been testing the Opel Astra Diesel Hybrid. There have been no concrete dates suggested for these vehicles, but press statements have suggested production vehicles would not appear before 2009.

So far, production diesel-electric engines have mostly just appeared in mass transit buses. Current manufacturers of diesel-electric hybrid buses include New Flyer Industries, Gillig, Orion Bus Industries, and North American Bus Industries. In 2008, NovaBus will add a diesel-electric hybrid option as well.

 Benefits

Benefits of the hybrid design include:

• Current hybrid vehicles reduce petroleum consumption (compared to otherwise similar ICE vehicles) primarily by using three mechanisms: a) Reducing wasted energy during idle/low output, generally by turning the internal combustion engine off; b) Recapturing waste energy (i.e. regenerative braking); c) reducing the size and power of the ICE engine, and hence inefficiencies from under-utilisation, by using the better torque response of electric motors to compensate for the loss in peak power output from the smaller internal combustion engine.
• Hybrids may also make more aggressive use of other fuel-saving techniques, such as reduced weight; these are not advantages of the hybrid design, but engineering choices made for various reasons, including marketing to consumers conscious of these issues.
• Trade-offs include higher weight for electric motors and batteries, which may reduce fuel efficiency at highway speeds compared to otherwise equivalent ICE vehicles, or even result in lower fuel efficiency at highway speeds than in urban use; for this reason, hybrids may be considered to be particularly well suited to urban applications.
• The internal-combustion engine in a hybrid vehicle is smaller, lighter, and more efficient than the one in a conventional vehicle, because the combustion engine can be sized for slightly above average power demand rather than peak power demand. A standard combustion engine is required to operate over a range of speed and power, yet its highest efficiency is in a narrow range of operation—in a hybrid vehicle, the combustion engine operates within its range of highest efficiency. The power curve of electric motors is better suited to variable speeds and can provide substantially greater torque at low speeds compared with internal-combustion engines.
• Like many electric cars, but in contrast to conventional vehicles, braking in a hybrid is controlled in part by the electric motor which can recapture part of the kinetic energy of the car to partially recharge the batteries. This is called regenerative braking and contributes to the higher efficiency of hybrid cars. In a conventional vehicle, braking is done by mechanical brakes, and the kinetic energy of the car is wasted as heat.
• Hybrids' greater fuel economy has implication for reduced petroleum consumption and vehicle air pollution emissions worldwide^[13]
• Reduced wear on the gasoline engine, particularly from idling with no load.
• Reduced wear on brakes from the regenerative braking system use.
• Reduced noise emissions resulting from substantial use of electric engine at low speeds, leading to roadway noise reduction and beneficial noise health effects. Note, however, that this is not always an advantage; for example, people who are blind or visually-impaired, and who rely on vehicle-noise while crossing streets, find it more difficult to do safely.
• Reduced air pollution emissions due to lower fuel consumption, leading to improved human health with regard to respiratory and other illness. Composite driving tests indicate total air pollution of carbon monoxide and reactive hydrocarbons are 80 to 90 percent cleaner for hybrid versus conventional vehicles[4]. Pollution reduction in urban environments may be particularly significant due to elimination of idle-at-rest.
• Increased driving range without refueling or recharging, compared with electric vehicles and perhaps even compared with internal-combustion vehicles. Limitations in range have been a problem for traditional electric vehicles. Hybrids may have substantially longer "operating hours" per unit of petroleum in certain conditions than the mileage-rated fuel efficiency figures may indicate, due to the reduction of idle-at-rest.

 Incentives

In order to encourage the purchase of hybrid vehicles, several incentives have been made into law:

 United States

• Starting January 1, 2006, the purchase of hybrid cars qualifies for a tax credit up to $3400 on the purchaser's Federal Income Taxes. The tax credit is to be phased out two calendar quarters after the manufacturer reaches 60,000 new cars sold in the following manner: it will be reduced to 50% ($1700) if delivered in either the third or fourth quarter after the threshold is reached, to 25% ($850) in the fifth and sixth quarters, and 0% thereafter.
• Hybrid purchases before January 1, 2006 qualify for a tax deduction on the IRS 1040 form. In 2003 hybrid owners qualified for a $2,000 deduction; the deduction reduces by $500 each year until it reaches zero. HR 1308 Sec. 319 proposed the phasing out of the deduction to put on hold for the year 2004 and 2005; (i.e., hybrid car buyers can enjoy the $2,000 deduction before the phasing-out resumes at $500 in 2006).
• Many states give additional tax credits to hybrid car buyers
• Certain states (e.g., New York, California, Virginia, and Florida) allow singly-occupied hybrid vehicles to enter the HOV lanes on the highway. Initially, the Federal Highway Administration ruled that this was a violation of federal statute^[14] until August 10, 2005 when George W. Bush signed the Transportation Equity Act of 2005 into law.
• Some states, e.g. California, exempt hybrid cars from the biennial smog inspection, which costs over $50 (as of 2004).
• Hybrid cars can go on certain toll roads for free.
• The city of San Jose, California issues a free parking tag for hybrid cars that were purchased at a San Jose dealership. The qualified owners do not have to pay for parking in any city garage or road side parking meters.
• City of Los Angeles, California offers free parking to all hybrid vehicles starting on October 1, 2004. The experiment is an extension to an existing offer of free parking for all pure electrical vehicles.
• In October, 2005, the City of Baltimore, Maryland started to offer discount on monthly parking in the city parking lots, and is considering free meter parking for hybrid vehicles. On November 3, 2005, the Boston Globe reports that the city council of Boston is considering the same treatment for hybrid cars.
• Annual vehicle registration fees in the District of Columbia are half ($36) that paid for conventionally vehicles ($72).

 Canada

• Residents in Ontario, Canada can claim a rebate on the Provincial Retail Sales Tax of up to $2,000 CDN on the purchase or lease of a hybrid vehicle. ^[15]

United Kingdom

• Drivers of hybrid vehicles in the United Kingdom benefit from the lowest band of vehicle excise duty (car tax) which is based on CO₂ emissions. In London, these vehicles are also exempt from the £8 ($14) daily congestion charge in central London.

 Trade-offs

In some cases, manufacturers are producing hybrid vehicles that use the added energy provided by the hybrid systems to give vehicles a power boost, rather than significantly improved fuel efficiency compared to their traditional counterparts.^[16] The trade-off between added performance and improved fuel efficiency is mainly something controlled by the software within the hybrid system. In the future, manufacturers may provide hybrid-owners with the ability to set this balance (fuel efficiency vs. added performance) as they wish, through a user-controlled setting.^[17] Toyota announced in January, 2006 that it was considering a "high-efficiency" button.

It has been observed that the success of the hybrid systems comes despite the need to carry two complete power systems. In a poorly designed car this might increase the weight and size and therefore greater losses in acceleration and aerodynamic drag, although the Prius is lighter and more aerodynamic than many other cars. In fact, the relative desirability of this concept rests on the deficiencies of the two underlying systems: the unfavorable torque curve of the internal combustion engine, referred to above, and the lack of a system of storing and delivering electrical power with anything near the energy density of combustible liquid fuels, so that a fuel tank, internal combustion engine, and generator together still represent a better source of electrical power than the equivalent weight and volume of batteries. In the event of relatively large leaps forward in battery or fuel cell technology, the internal combustion portion of the hybrid will become superfluous. Somewhat less likely is the possibility of a change in the general popular mode of automobile use largely supplanting short trips by use of mass transportation, so that the majority of automotive operation becomes steady speed cruising rather than stopping and starting; this would eliminate the advantage gained from regenerative braking and the low rpm torque boost of the electrical portion of the hybrid, and allow very small forced induction internal combustion engines to become viable competitors of the heavier hybrid systems.^{[citation needed]}

Skeptics claim that mechanics are not fond of working on hybrid vehicles due to added complexity, but the Toyota mechanics in Atlanta and other U.S. cities say they are delighted by the cars, and hundreds of enthusiastic engineer-owners gather on the Internet and in clubs. The complexity may result in greater repair costs, although hybrid manufacturers typically encourage buyers with generous warranties so this has not yet affected end users. These vehicles have been available for ten years and the lifespan and resale values are good. In fact, the vehicle that has kept its resale value the best from 2004-2006 is a hybrid vehicle, and another two hybrids are in the top ten ^[18]. Hundreds of thousands are in use, but Toyota reports very few problems with battery packs. One additional problem is the lack of towing hook, the hybrid cars have limited power resources so often they can not be used for high power applications such as towing boats.

Disposal is an additional issue. By its nature, a battery must be made of reactive chemicals; the more power density the battery offers, the more reactive the chemicals it contains. However, all discarded hybrid vehicles will be returned for proper recycling and disposal; dealers and mechanics are trained for this, and rigorous regulations are in effect. Virtually all automobile batteries in the U.S. are recycled, and the environmental effects of leachates from the small number of hybrid battery packs that are not recycled will be no worse than they are from ordinary automobile batteries. (The Prius battery pack is only a little larger than the starter battery.)

Hybrid vehicles are more expensive than traditional internal-combustion vehicles. The trade-off between higher initial cost and lower fuel costs (often referred to as the payback period) is dependent on usage - miles travelled, or hours of operation, and fuel costs. Traditional economy vehicles may result in a lower direct cost for many users (before consideration of any externalities.

Finally, a two-year study by CNW Marketing Research^[19] could suggest that the extra energy cost of manufacture, shipping, disposal, and the short lives of these types of vehicle outweighs any energy savings made by their efficient propulsion system, thus their total dust to dust energy cost is potentially higher.

Hybrids vs. electric vehicles

Battery powered all-electric cars (BEVs) are more popular in Europe than in the U.S. (Most European electric vehicles are purchased from manufactures, while due to unavailibilty of manufactured vehicles, most U. S. vehicles are owner produced conversions of older conventional vehicles.) The major U.S. automobile manufacturers argue that customer demand for pure electric cars is small. In addition, the long suburban commutes common in the U.S. make range an important criterion for electric vehicle design. However, if advances in battery technology allow increased range at comparable cost to gasoline-powered vehicles, manufacturers will likely mass-market electric vehicles. The relative cost of gasoline to an equivalent amount of electrical energy will also be a critical factor in the electric vehicle market.

Another relevant factor is the ultimate source of power for the electric vehicles. In areas where older coal-fired generators are the source of electrical power, a pure electric vehicle will be responsible for more of some types of pollution, namely sulfates and particulates than a hybrid vehicle, while less of others, such as carbon monoxide and nitrogen oxide emissions (Table 1). Whether greenhouse gas emissions will be lower in such a case is still under debate [5] vs. [6]. In any event, the local pollution effects would be lessened by a fleet of electric cars, because the sources of the pollution would be outside of urban areas.

An advantage of the hybrid vehicle is in not requiring any upgrades to the electric power transmission grid. Since it can't be scaled larger and smaller at will, the grid is sized so as to carry almost the maximum load (i.e. summer air conditioning) with only occasional failures, and thus has much of its capacity idle most of the time. For the electric utilities, it would be advantageous to utilize that excess capacity and thereby generate a greater revenue for their fixed investment, by selling power to consumers to recharge their vehicles. However, this vision very pointedly does not allow for recharging of vehicles during peak usage times; to do so would require substantial upgrades to the capacity of the grid, and again leave the utilities with excess capacity most of the time. On the other hand, to require consumers to refrain from recharging their vehicles during certain times may not be an easy idea to sell to them.

For now, car manufacturers are focusing on fuel cell-based cars and hybrids. Fuel cell vehicles are being developed in a long-term research environment, rather than with expectations of production at any defiinite time. Toyota intends all of its vehicles to have a hybrid option by 2012.^{[citation needed]}

Plug in

After market plug in kits are available for some hybrids from third party manufacturers. These greatly increase mileage per unit of petroleum (although overall energy consumption may be the same). Cost savings, toxic pollution and greenhouse gas production will depend on the local electric regime. If electricity generation is located elsewhere, it may reduce local emissions of toxins, an advantage in urban areas. See Plug-in hybrid electric vehicle