Back in February, when I was still eagerly awaiting the delivery of my new electric-powered BMW i3, I described how dramatically lower running costs was one of the main factors influencing my decision to “go green”.
Last week, with just under 4,000 miles on the odometer, I felt it was about time to see if those running costs really did meet the 2p per mile claim put forward by BMW and the Office for Low Emission Vehicles. But this was not as easy a task as I had imagined…
I had wrongly assumed that information on the amount of electricity put into my car would be easily available but, despite many phone calls, this turned out not to be the case. I have kept track of every drop of fuel that has gone into running the car’s range extender, which is all you would need (along with the record of total mileage) to calculate a regular car’s mileage per gallon, but the BMW does not keep a record of electricity input.
In the end it required a handy smartphone app called iRemote (which separates the car’s total mileage from the amount run on the battery), some information from the instrument display and the support of two very able Transport Systems Catapult engineering undergraduates to arrive at the figures below…
Starting with the range extender, I could see by using the app that 16.8% of my driving had relied on conventional fuel – meaning that the 59.72 litres of fuel I have pumped into the car since March has got me 666 miles, giving a better-than-expected average consumption rate of 50.7 mpg. Since I had kept receipts for all my fuel purchases, I was able to calculate that this equated to 11.78 pence per mile while using the range extender. That certainly compares favourably to the 20 pence per mile in fuel that I was spending on my previous (regular) car, but it’s worth pointing out that I now only need to use conventional fuel on longer journeys – often cruising at 60-65 mph, so fuel consumption is likely to be less efficient when using the range extender in urban areas.
Turning to the vital matter of the car’s electric running costs, I now knew that I had clocked up 3,290 miles on battery power (out of a total of 3,956 miles), but keeping a tally of the cost of that electricity is a good deal harder than collecting service station receipts. The difficulty lies in keeping track of the amount of battery charging done at home and the amount done at public charging points. As most of these charging points are, fortunately, still cost-free I try to minimise my charging at home, where I pay 13.4 p/kWh, and I have estimated that around 80% of my charging has been at free points.
My car display tell me that my actual average electricity consumption has been 15.2 kWhr/100 km which translates, in imperial measurements, to 4.1 miles per kWh on battery power. So to cover 3,290 miles, I have had to use 805 kWh’s, paying my home electricity provider for an estimated 161 of those kWh’s at a total cost of £21.57 – or 0.66 pence per mile. I hope that you’re still with me by the way…!
Combining the fuel cost and the estimated electricity cost (and bearing in mind the weighting of 16.8% fuel compared to 83.2% electric), I arrived at a total running cost of 2.53 pence per mile.
As I accumulate more mileage over the next few months, I will try to assess the accuracy of that estimated 80:20 split between free and paid electricity. Based on this first set of calculations, however, I would say that the real running costs are not too far removed from those given by the manufacturers, and are clearly much better than the fuel costs associated with conventional cars.
Of course, fuel is only one aspect of a car’s total running costs, and electric car owners still have a higher initial outlay to consider when purchasing their vehicle. It is good to know though that those lower energy costs – combined with road tax exemption and cheaper, or even free, parking in some areas – are helping electric car owners to claw back some of that initial investment cost.
Over time, I expect that more and more charging points will be paid for, which could of course make a big difference to the cost of running an electric car in the future. But that may be a price worth paying if it also leads to charging points that perform better and are more readily accessible. The UK government has already pledged that by the end of this year every motorway service station will be fitted with the new 50kW DC rapid charging systems – allowing drivers to recharge to 80% capacity in just 30 minutes.
That will certainly be a welcome development, provided that drivers can actually access the points, which hasn’t always been my experience to date. Indeed, the only rapid charge point that I have found near me (just off junction 14 on the M1) is constantly blocked by conventional cars that have been parked in a way that prevents access to the charge point. In order to avoid frustration and wasted investment, it is essential that charging points are always located alongside dedicated parking bays.
By Steve Yianni. Source
