You get the best of both worlds with a hybrid car, a petrol engine and electric motors.

Hybrid cars have a conventional petrol engine with an electric motor, are economic and reduce carbon dioxide emissions. Most hybrid cars can run in electric-only mode and when they do, they emit zero carbon dioxide. Hybrids are useful cars to drive in urban areas or when you are stuck in traffic.

How do hybrid cars work?

The energy used by the electric motors is stored in rechargeable batteries. An onboard computer system decides whether to use the petrol engine or electric motors based on maximum efficiency.

Not all hybrid systems are the same. A study conducted by Channel 4, reveals that different hybrid systems use different combinations of energy sources. The study says, 'The Honda Insight, for example, will use the petrol engine only when moving off from rest and at low speeds, but when accelerating, its computer asks the electric motor to chip in with extra help. As cruising speeds are reached, the electric motor is turned off, leaving petrol power only. As the driver starts to slow down – and this is the clever bit – the electric motor becomes a generator and transfers the kinetic energy of the car into the battery as electric power.

This is called 'regenerative braking'. Whenever the car comes to a stop, the computer turns off the engine to save fuel and CO2 emissions.'

Green ratings

Electric and hybrid cars are at the top of the Department of Transport’s A and B rating bands. They have CO2 emissions that are below 100g/km (Band A) or between 101 and 120g/km (Band B). The rating bands range from A, the most environmentally friendly cars to G, cars with the highest CO2 emissions.

There is a downside to driving green

It’s not easy driving green, here are some of the disadvantages:

• Hybrids can be more expensive than conventional cars

• If you drive mainly on the motorway, hybrids are not as economical

• City driving can drain battery power. When the battery runs out of energy, the petrol engine takes over.

• There’s not a lot of boot space. Most of it is taken up by the electric-power train and batteries.

• Beware of battery toxicity. Most modern hybrids use recyclable NiMH batteries instead of NiCad.

How much does a hybrid cost?

Hybrid cars are holding their resale value due to their current popularity. However, as the Channel 4 study points out, 'Overall, given the high purchase costs compared to a mainstream car, a comparable diesel-engine model is often cheaper to run – and emits less carbon dioxide.'

Maintenance costs are comparable to conventional cars. However, dealer service centres usually charge more for servicing a hybrid car. Experts say that the overall maintenance on a hybrid car should cost less than its petrol and diesel counterparts. This saving is due to less wear and tear on the engine and braking system.

Hybrid battery packs are designed to last between 150,000 and 200,000 miles. If you calculate the saving over the life time of the car, you save on the total running costs. Plus, you qualify for lower tax bandings and could be exempt from London’s congestion charge.

What does the future hold?

Technology is improving every day. Hydrogen fuel cell technology could eventually replace the hybrid car as the most environmentally friendly vehicle on the road. Unfortunately, most experts will tell you that it’s not likely to happen for another 10 to 20 years. The first hydrogen-powered cars will most likely have more than one energy source, so will in effect, be hybrid cars too.

Whether you decide to go green and drive a hybrid or stick with what you know and drive a car powered by petrol, make sure you have adequate car insurance. You never know when you will need it.