In 2008, a fairly glowing report written for BERR (the Department of Business, Enterprise and Regulatory Reform) predicted that the energy use of electric cars would be 0.26kWh (kilowatt hours) per kilometre by 2010. That implied very low running costs and significant CO2 savings compared with petrol or diesel.
More recently, a study published in April by the Department of Energy and Climate Change (DECC) claimed that in the light of soaring oil prices it is cheaper to run an electric car over four years than it was to rely on an internal combustion-engined one.
On the basis of these findings, the DECC sanctioned the construction of 11,000 charging points in supermarkets, street and car parks at a cost of £400million over the next 18 months.
The point of the exercise makes sense: to demonstrate that the high initial outlay for an electric car can be recouped over time. Unfortunately, the DECC doesn't appear to have made a proper analysis, instead using a very selective calculation designed to show electric cars in the best light.
First, it compared its electric car (the Nissan Leaf family hatchback) with a petrol-engined rival, rather than one of the new super-efficient diesels that combine good fuel economy with zero road tax.
Second, unlike most analysis of running costs, it ignored the extra capital costs of the electric car, which allows for interest on the capital assuming it had been invested in a good savings account and taxed at the basic rate.
Thirdly, DECC assumes that cheap overnight electricity at rock-bottom domestic prices is mostly used to charge the electric car in question, which is unlikely if commercial charging points are used during the day.
And finally, the calculations gloss over the fact almost 60 per cent of the current price of petrol and diesel is tax, which will inevitably clobber the presently untaxed electric motorist in some form or other as the take-up of electric vehicles increases and the revenue from fossil fuels diminishes.
For a fair comparison, it makes more sense to compare the £30,995 Leaf with a diesel rival such as the £18,665 Volkswagen Golf Bluemotion TDI. The revised calculation shows that the electric car works out £850 a year more expensive to run than the diesel – enough to buy more than 600 litres of fuel for 9,000 miles or so of motoring.
And, while CO2 emissions are undoubtedly lower for the Leaf compared with petrol cars, they are the same as those of the very latest diesels. For a true answer, however, a more in-depth analysis is required than this simple DECC approach.
We'll start with CO2, for although electric cars are often given the "zero emissions" moniker, unless they are run on electricity produced entirely from renewables they merely shift pollution elsewhere – from city centres to power stations.
When testing the Leaf, the US Environment Protection Agency (EPA) found that its average range over varied driving conditions was 73 miles after an eight-hour charge, with average energy consumption at 0.34 kW per kilometre. This is about 35 per cent greater than the BERR prediction but still about half the energy use of the 1.6-litre diesel-engined VW Bluemotion (0.65 kWh per mile).
You might think that because the Leaf is twice as energy efficient as even the most efficient diesel car, its CO2 emissions must be lower. However, when you take into account the fact that most of the UK's electricity is still generated by fossil fuels, that is not the case.
We need to look then at the amount of CO2 produced by power stations in the UK. This varies according to demand, which in turn varies with the time of day and season, but in 2009 averaged 544g of CO2 per kWh. Using the EPA's 73-mile range figure, this translates to CO2 emissions of 126g/km for the Leaf.
The VW Golf Bluemotion has a quoted CO2 output of 99g/km. If this is inflated by 10 per cent to account for a more realistic economy for those who do a lot of city driving, it becomes 110g/km. To be completely fair, the diesel figure should also be adjusted to account for CO2 produced getting the diesel to the pump, from extraction through to refining and distribution – losses of about 10 per cent.
This gives the so-called "well to wheels" (WTW) figure, which for the Golf is about 121g/km – more or less the same as the electric Leaf.
Another important factor is the considerable extra drain on the battery in an electric car when using the heater during cold weather, which can reduce the range considerably. In petrol and diesel cars, heating the cabin is free, using waste heat from the engine.
Using the simplest calculations and based on electricity alone, the Leaf costs about 1.7p per mile to run if charged at off-peak rates (which currently bottom out at 5p per kWh). Using peak rate electricity at 12p per unit pushes the cost up to a still modest-sounding 4.1p per mile.
This compares with a cost of 9.6p per mile for the diesel Golf, assuming a price of £1.42 for a litre of fuel. However, to be completely fair you have to consider that the actual cost of diesel, when duty and VAT is removed, is less than 60p per litre, representing a "real fuel" cost of only 4.1p per mile.
Why does this matter? Well, if there is a significant take-up of electric cars the government is unlikely to forgo a chunk of the £40 billion raised every year from motoring taxes. Nor could it tax electricity in general, in the process clobbering households using it for heating and cooking, so the most likely way this tax could be recouped is by the introduction of road pricing, which would have to average about 10p-15p per mile for tax neutrality.
Not only this, but the current tax-free perks associated with electric cars could well disappear, and while oil prices are probably going to escalate, the last few years have shown that electricity prices are quick to follow suit, having doubled since 2007.
Strain on the grid
If everyone were to switch to electric cars immediately, there would be an average increased demand on the National Grid of about a third of the UK's peak electricity generation. This assumes that everyone would charge their cars at random times, equalising the load on the grid. In practice there could be huge surges if lots of people decided to charge their cars at the same time – just after getting home form work, for example.
If everyone were to charge their vehicle overnight during the "Economy 7" period for the cheaper tariffs, the demand would be around three times greater – or almost the entire current UK peak winter electricity use.
To put this in perspective, even a 50 per cent take-up of electric cars, spread over the next 10 years or so, is unlikely. The figures quoted illustrate the infrastructure and logistics needed to prepare for the change-over.
Even during the small hours, between 40 and 50 per cent of our power stations are currently working flat out during the winter, therefore the amount of spare capacity is limited. If more people are using off-peak power, the price is also likely to increase.
A so-called "smart grid" would have to be built to allow for extra power to flow within urban areas at peak times. Smart meters, which monitor households' power use minute by minute and feed information back to the power companies, will help to control charging times and prices. And, of course, all those electric car charging stations will have to be established.
The conclusion from all of this is unavoidable: the panacea of electric motoring for all isn't as clear cut as some would like you to believe, to the point where it's almost impossible to see how it could become a viable option, certainly in the shorter term and without massive investment.
Perhaps ultimately hydrogen will become a serious option, or scientists will work out how to harness nuclear fusion for our day-to-day mobility requirements.
In the meantime, you begin to realise how good petrol and diesel are. If they didn't exist already, we would probably have invented them.