Steve Walker
26/04/2011 08:14 | By Steve Walker

Hybrid cars – pros and cons



Hybrid cars - should you be driving one? (© Honda)

You'll probably have heard about hybrid cars, they're big news at the moment with most manufacturers either developing hybrid technology or already offering it to customers.

Hybrids have generated yards of column inches, been endorsed by nightclub loads of celebrities and are routinely pushed forward as the most viable short-term answer to the motor car's environmental woes.

The question is whether or not you should consider taking the plunge and choosing a hybrid as your next car. As part of our Green Car Guide, we're attempting to provide the answer. Here goes...

Green Car Guide

The top hybrid cars on sale

C
ars that avoid road tax

What are hybrids?

Porsche Cayenne Hybrid (© Porsche)

The main problem with conventional cars is that they burn fossil fuels. The main problem with electric cars is that they have a limited range. The hybrid car is a halfway-house solution to these issues which combines an electric motor with an internal combustion engine.

The electric assistance allows the conventional engine to work less hard, so less fuel is burned and emissions are reduced. Hybrids use the car's kinetic energy to recharge their batteries so they can maintain their power reserves, ready to muck in when the driver puts the pedal to the metal.

Are all hybrids the same?

Lexus GS450h (© Lexus)

There are various different types of hybrid: at one end of the scale, some cars are marketed as hybrids when the kinetic energy they recover only helps to run the electrical systems in the car. In models like the Smart Fortwo MHD (Micro Hybrid Drive), there's no electric motor to provide motive force but much of the strain of charging the battery is removed from the engine, saving fuel.

Many manufacturers, notably BMW and MINI, fit these systems to their cars but leave the term 'hybrid' out of the equation. You'll see the technology described as 'regenerative braking' or a 'kinetic energy recovery system' so buyers should make sure they know what they're getting.

The majority of hybrid models on sale around the world are 'parallel' or 'mild' hybrids - cars like the Honda Insight and Civic Hybrid. They offer electric assistance to their internal combustion engines under acceleration but in current models neither the electric motor nor the internal combustion engine can drive the wheels without the other assisting.

The more advanced 'series/parallel' or 'full' hybrids like the Toyota Prius, the Porsche Cayenne Hybrid and the Lexus RX450h can theoretically run on any combination of petrol and electric power.

Honda Insight (© Honda)

In practice, to get enough power to run as an electric vehicle for a meaningful distance, full hybrid models are increasingly becoming available as so-called plug-in hybrids. These vehicles have larger battery capacities and give owners the option of charging the car from a mains power supply. This provides a power boost that theoretically means they'll only have to resort to their internal combustion engine on longer journeys.

Yet another variation on the theme is the 'range extender' hybrid. These cars are driven exclusively by an electric motor but have an internal combustion engine on board too. That engine is only used as a generator to charge the batteries from which the electric motor and other systems then draw power.

Somewhere between a hybrid and a full electric vehicle, range-extender models like the Vauxhall Ampera aim to answer concerns over range and long charging times that make today's electric cars problematic for anything other than short-trip urban use.

How green are they?

Toyota Prius plug-in hybrid (© Toyota)

The green credentials of a hybrid car depend greatly on what kind of hybrid it is and how it's used. By taking the strain off the internal combustion engine, the electric motor will always reduce fuel consumption to an extent but the batteries add weight to the vehicle, forcing the drivetrain to work harder.

There's also the issue of recharging the batteries. Hybrids recover kinetic energy when coasting or under braking. When driving for prolonged periods in stop/start traffic, they don't get as much opportunity to do this and so the electric motor can't always provide the same level of assistance.

To deliver their best economy and emissions, hybrids need journeys with enough downhill coasting and braking to charge their batteries or a plug-in system to keep the batteries topped up. On long, high speed motorway trips that force hybrids to lean more on their internal combustion engines, the fuel economy benefits are limited.

Lexus CT200h (© Lexus)

The batteries themselves are something of a sticky environmental issue. Not only will the increased demand for hybrid vehicles put pressure on the raw materials needed to make batteries, dangerous metals and chemicals in the batteries must be disposed of at the end of the car's life. The more hybrids on the road, the bigger these problems become.

The hybrid cars you can buy today overwhelmingly use petrol engines but models mating diesel engines with electric motors like Peugeot's 3008 HYbrid4 are starting to emerge. Diesel hybrids should achieve even better fuel economy figures by virtue of the inherent efficiency of diesel cars.

Eventually, hybrid cars may not have internal combustion engines at all. Most prototype fuel cell vehicles are hybrids of a kind with power from a hydrogen fuel cell stack and a brake-energy regeneration system both used to charge their batteries.

Should I buy a hybrid?

Peugeot 3008 HYbrid4 (© Peugeot)

As you may have gathered from all this, the term hybrid is more complex than it might appear at first glance. As a result, the question of whether you should buy one is too.

Brake-energy regeneration and stop-start technology are already commonplace in all kinds of cars that we wouldn't class as hybrids and they're only going to get more so. If we limit our definition of hybrid to cars with wheels that are driven exclusively or in part by electric motors, the choices are much more limited but again, that's changing fast.

The official fuel economy figures for these vehicles are undeniably attractive but how close owners get to them in real-world driving depends greatly on how and where they drive - much more so than with a conventional car.

Many motorists will find that they achieve better fuel economy in a car powered by one of the latest diesel engines than they do with a hybrid.

What won't vary from owner to owner are the CO2 emissions levels. In this case, the official figures are gospel and so hybrids yield big tax advantages over equivalently powerful conventionally engined cars. Low levels of hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases also help the hybrid's environmental standing.

Volkswagen Touareg Hybrid (© Volkswagen)

Hybrid cars won't be for everyone, at least not yet. We haven't seen a hybrid go on sale that will fully satisfy the keen driver, although sportier models like the Honda CR-Z hint that such a car probably isn't too far away.

Those who adopt a more relaxed driving style and appreciate low-speed refinement will feel more at home in the affordable hybrids currently on the market. Manufacturers like Lexus and Porsche have also used hybrid technology to make their powerful luxury saloons and SUVs greener and more affordable to run.

In all cases, the greater complexity of hybrids means they're priced above conventionally powered cars so the crucial point for most buyers will be whether or not the tax and fuel savings make a hybrid a viable option for them.

Pros: Low emissions, fuel economy, refinement
Cons: Price, not suited to all journey types

 
CarPricecombined MPGCO2 (g/km)0-62mph (s)
Honda Insight 1.3 IMA SE£16,67564.210112.5
Toyota Prius T3 1.8 VVT-i£20,69572.48910.4
Honda CR-Z 1.5 V-TEC S£17,36056.51179.9
Porsche Cayenne Hybrid S£59,05834.41936.5
Lexus LS 600h£93,85030.42186.3


Green Car Guide

Petrol or diesel?

Electric cars

Fuel cell cars

Biofuels - should your car be using them?

The most economical cars in each class

Car fuel economy - the truth about MPG

CO2 and other car emissions explained

Range anxiety - the curse of the electric car?

How to save fuel - green driving tips


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3Comments
28/04/2012 21:55
avatar
Think I can speak for a fair few Prius drivers. The main attraction is the very low benefit in kind when having this as a company car. I switched recently from a VW Jetta and halved my benefit in kind. The MPG is only great if you drive reserved, I don't drive mine too much different from my Diesel Jetta so do struggle to get good MPG on A roads and Motorways.
28/04/2012 13:41
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personally I drive a 2003 Honda Civic ima, not a bad car, comfortable, frugal, road tax £30, exempt from the congestion charge, I found out that it doesn't like Hardknott Pass though.
28/04/2012 10:27
avatar

Toyota Prius Vs Golf TDI ?

 

Better mpg ,less impact on enviroment, and credibility.

Why buy a Prius?

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