What about hybrids and 'plug in' hybrids (PHEV's)

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Hybrids are electric cars which generate their own electricity from a petrol engine, with some energy stored in a small battery which allows small distances to be driven without  running the engine.  

• Lower fuel consumption and CO2 Emissions especially in stop/start driving with  fuel consumption of a petrol model similar to that achievable by a diesel engine model but without the high emission of unhealthy particulates (PM2.5's etc) .
• No gearchanges or hill starts necessary - Most Hybrids offer an 'Automatic Transmission' as standard.

• More complex machine with engine plus motor/generator and an advanced battery system , however reliability and life of Toyota Prius is outstanding, showing well engineered examples perform well.
• Some issues arising with pollutants that arise as petrol engines run cold; these are as yet unregulated.       Hybrids found to emit higher levels of harmful emissions than diesels | This is Money 
• Overall CO2 reduction possible with a Hybrid is small, one can expect to save 3 times as much CO2 emissions switching to an Electric Car. following link includes some good data: How much CO2 can electric cars really save? (transportenvironment.org) 

MILD HYBRIDS (48 Volt Hybrids)

These are a further class of Hybrids which use a small battery and electric motor to assist the engine, giving efficiency improvements and slightly lower CO2 emissions. These cars are sometimes known or badged as 48V Hybrids - by Hyundai in particular. They are a halfway house between a conventional car and a hybrid, and are available with a manual gearchange (or 'stick shift' in the USA). There was a school of thought that 'Mild Hybrids' would make a significant contribution to reducing carbon emissions in transport, however this was only ever a 'stepping stone' on route to low carbon transport , and Joe believes that this technology is now by-passed by more efficient and lower carbon alternatives. 

Plug in Hybrids incorporate a larger battery than Hybrids, and allow this battery to be charged with mains electricity from a home or public charger. Once charged (either from the petrol engine or from the mains) they can drive some distance (15-50 miles) without the engine, i.e. on electric power.

• No 'Range Anxiety' car has very substantial range, and can be refuelled at a petrol station in minutes to allow continuous driving.  
• If battery is charged from the mains, rather than by the petrol engine, the vehicle is efficient and has low emissions when running on electric  power for its  range of 15-50 miles. If vehicle is used for short runs and is charged only with mains electricity, it is efficient and has low emissions. 
• For Manufacturers and Dealers PHEV's use the components and skills they have built up over decades selling, manufacturing and servicing petrol and diesel cars. Many service items  and much regular servicing (oil changes etc)  is needed, maintaining  their current service staff and business model. 

• Low efficiency when operating on the petrol engine, as less than 40% of the energy consumed in a petrol engines can be turned into electricity to drive the car.  Mains power generated (in the UK anyway) is produced more efficiently with lower CO2 emitted. 
• Vehicle includes most of the parts of a petrol car and those of an electric car, giving a heavy  and complex machine with much 'embedded' CO2.   
• Carbon footprint is likely to be lower than that of similar sized petrol car, but around three times higher than that of an equivalent electric car. Calculations from 'Transport and Environment" show Hybrid and PEV emissions compared with those of an electric car.

Operating only on mains electricity by limiting range to that possible on battery only, and recharging on home or public chargers could allow efficiency and CO2 footprint close to that of an electric car, however in reality few owners will operate them this way. Will the 'trouble' of putting a car on to charge seem worthwhile in a PHEV for range of just 20-50 miles? 

Official data being published by manufacturers about their PHEV's fuel consumption, electric range  and carbon emissions are highly misleading see Joe's Blog here with links to analyses.

Where electricity is generated mostly from fossil fuels - particularly coal, such as some states in America, Hybrids and Plug in Hybrids can approach the carbon efficiency of Electric Cars, however in the UK and most of Europe this is not the case.