Hot and Sandy

Travel writing, pictures and stuff for people I know. Quite a lot of cycling talk, and some semi-controlled ranting. Hiking, outdoor and two-wheeled stuff, perhaps a little computing when it's worth talking about. Meandering thoughts.

Wednesday, February 24

Cost of a full tank

18.8kWh x 11.93p TCR = £2.24 charge from "empty" (battery size is 22kWh but users can't deplete it fully). I've charged the battery almost 160 times. If each charge lasted 80 miles, this is a practical minimum cost of 2.8p/mi. Blimey.

Tuesday, February 23

i3 REX Additional Savings

Oops. It was pointed out to me the other day that my figures are even more pessimistic than I thought. At least half of the 'away-from-home' charges I've done were at the brilliant and totally free Ecotricity rapid charge points; I was using them daily at one stage (so I reckon about about 400kWh). This means that I've saved at least an additional £60 and the car is costing more like 3.3p/mi.

As well as this, I should have probably factored in the road fund licence (car tax) I have to pay on my old Audi, which would increase it's running cost to 13.5p/mi. Amazing!

Sunday, February 21

i3 REX Ownership Update

Well, the i3 is still a pleasure to use. It's fast and efficient, and I will never get tired of walking out of the house to a car that's warm, demisted and magically full of fuel!

Make no mistake: my use of the i3 was a marginal case when the minimum journey between charges was 100 miles. If I tried, I could hypermile around with the heater off, refuelling once every 5 trips (translation: empty the battery with about 20 miles of my commute left, refuelling with unleaded was buying me about 100 miles range per fill).

My journey profile is also a challenge: 52 miles each way consisting of motorways and dual carriageways - average speed has to be 50mph+ for an hour, and motorway sections 'flow' at 75mph.

Now though, my employer has installed electric vehicle charge points! They are mostly for fleet vehicles but I have an RFID card and have always bagged a space. On one occasion all of the points were down for maintenance, but I can still drive home using some petrol.

Let's talk BMW i3 REX cost of ownership / running costs:

Contrast these with the stats at 5400 miles (no work chargers):

Although the accounting for electricity is still in beta, I can make some inferences of how much I've used based on the delta between total consumption of the car and the smart-meter reading on my home charger. So far I think I've used about 830kWh of employer's electricity for which they have charged me £18, pre-tax *(see update). This is a huge bargain, considering the same charge would have cost about £95 on my home tariff - including VAT and the service charge.

So the numbers. Well my REX does 49mpg when it's running on petrol - much better then most online reviews claim. Normally this is 65-70mph on a dual carriageway. It's covered 13,432 miles and 84% of those have been electric. On electric I am averaging just over 3.8mi/kWh, slightly better than the BMW-published average.

In terms of running cost, I haven't paid any tax or maintenance yet and the numbers are 3.69p/mi combined and 3.13p/mi on electric. Actually there are a couple of reasons this is pessimistic: firstly I have modelled all electricity use at my domestic TCR, which is 11.95p/kWh. Since my employer's electricity is cheap this overstates the cost. Secondly I've been using the car since January 2015 so we've had a year of use containing most of two winters and one summer. Winter is the least efficient time in the UK for EVs, so this is probably a worst-case scenario. I would expect that the real running cost (excluding depreciation of course) would be below 3p/mi.

13.5k miles. One year of ownership. £1120 saved in fuel alone. Brilliant, practical and efficient vehicle. Delighted!