Leon wrote:

Hi SuperM,

Maybe this (fuel/electricity cost analysis is of help.

Your BMW:

Just looking at fuel costs of your daily commute. 30 miles in a car that does 60 mpg will cost you half a gallon. A gallon is 4.54609 litres. With fuel at £1.10/litre a 30 mile drive will cost you £2.49.

Audi A3 e-tron:

Assuming that an e-tron will get you 25 miles on a fully charged battery, you will have to use the petrol engine for the remaining 5 miles. At 11p/kWh a full charge of 8.8 kWh will cost you about £1. The remaining 5 miles will cost you £0.42 (again fuel at £1.10/litre and assuming 60 mpg: £0.083/m). Total cost (electricity and fuel) for your 30 miles stretch would be £1.42.

Conclusion: compared to your BMW the Audi A3 e-tron will be £1.07 cheaper per one-way commute of 30 miles. If you go to the office for 200 days, you will save £428 per annum on fuel cost alone. Note: this does not tale into account other cost and depreciation of course.

Another way of looking at it. If you manage to get 25 miles out of a charge at a cost of £1.00 for the electricity, you will save £1.08 on fuel compared to a car doing the same distance at 60 mpg with fuel at £1.10/l (again using £0.083/m fuel costs). Energy in is energy out. It doesn't really matter if you drive 25 miles or 300 miles, if you start with a fully charged battery any journey will save you £1.08. Perhaps the advantage is slightly more if you use the EV mode selectively, but not by much.

Bottom line: every time you fully charge and drive at least 25 miles you save about a pound. If you manage to charge the car at least every day and drive minimum of 25 miles per day you will save a minimum of £365 per year.

Makes sense? Any flaws in my thinking?

Thank you.

Almost, there are some flaws in your reasoning

.

* Diesel is less expensive than Gasoline in Belgium (0,15€/l), although the government will start reducing the gap

* The first miles with an ICU are the most expensive (cold engine), so I reckon I will be rather doing 40 mpg on those 5 miles I will use the ICU for my daily commute.

* I would no longer lease a 520d estate, but a smaller BMW (320d probably), the facelifted 320d should be at 4,1l /100 // 70 mpg on my daily commute, and 60mpg as a total average (compared to 51 mpg for the 520d today).

As a consequence, the difference in fuel cost will be smaller. The main issues are the long commutes. When driving towards the centre of France, averaging at 47 mpg with my 520D today, I will probably be rather at 40 mpg with the e-tron and 51 mpg with a 320d..

I will be charging the car twice a day btw

But for me the economics are not that important. I don't pay my fuel (company car). I just want to minimize my ecological footprint.

With my actual assumptions, I will produce 183 gr CO2/km with the e-tron compared to 193 gr CO2 for the BMW 320d (assumptions 688 gr CO2/kwH electricity and 1,62 kwH electricity/l for crude oil refining). But while I'm sure of my assumptions for the 320d (60 mpg overall), I'm less sure on my estimate for the e-tron (83 mpg + 15 kwH /mile).