Drive the car, tuppence a mile!

(To the tune of the popular Mary Poppins song.)

How much does it really cost to drive an electric car? Well, I've had my BMW i3 for a few months, so I thought I'd crunch the numbers.

As part of the UK Government's OLEV scheme, there's a subsidy for installing car charging points at home. One of the conditions of the subsidy is that a smart meter is installed which reports back details about the energy used to charge the car (aside: wonder if that's available as Open Data?). This means I know exactly how many kWh the car has gobbled up at home.

OLEV Smart Meter

My car tweets its stats (thanks to some hacking).

I'm with Ovo Energy (join Ovo and get a £25 Amazon Gift Card). They charge me £0.1308 / kWh.


517kWh * £0.1308 = £67.62

£67.62 / 4,118 miles = 1.6 pence per mile

ZOMG! That's half as much as I originally predicted! For comparison, driving a fairly efficient hybrid was costing me 10.4 pence per mile.

I also have solar panels - they've been performing pretty well this year.

Solar Generation 2015-fs8

I got the car in September, between then and now they've generated ~930kWh. A little under double my car's consumption. So, from a certain point of view, I've been driving on free sunshine ☺


OK... So that's the costs to me, but what are the real costs?

There was one major up-front capital cost (which can be amortised) - installing a charging point in the garage. The normal cost is ~£200 but we had to dig a small trench in my garden for the wiring, so it came to around £300. The fine folk at EV Charging Solutions did a beautiful job of installing everything.

My i3 has a 9 litre petrol tank which kicks in if the battery is getting low. So far I've put in less than a fiver of unleaded.

There are a number of free charging networks in the UK. I occasionally use Ecotricity's Electric Highway for rapid charging on motorways.
Twice I've used Source London's chargers in car parks - that cost £5 for membership but is free for now.

But, the real subsidy comes from my employers. They're keen on reducing their employees' impact on the environment, so they offer free chaging at work. I can do my 75 mile round trip to work without charging, but more often than not I plug in for a boost (when the Pod-Points aren't broken).

As I'm an excellent driver (!) I average around 4.2 miles per kWh.

4,118 miles / 4.2mi/kWh = 980 kWh used

So I charge a little over half the time at home and the rest for free. If I were paying the domestic rate for the electricity, it would cost me around 3p per mile.

Final Thoughts

Electric cars are great! If you can afford the up-front price, the running costs are ridiculously low.

The only fly in the ointment is the proposed costs from some of the free networks. We've already started to see companies like ChargeMaster introduce minimum fees of £1.20 for their "free" network - that starts to make charging uneconomical.

The i3 costs around £2.50 to fill from empty to full on a domestic tariff. How much extra is it worth paying to charge away from home? At the moment, most of the networks are staying quiet on whether they'll charge per minute, per kWh, per connection, or something else.

As more houses get solar panels and take advantage of free power from the sky, asking people to pay a premium for an electrical connection becomes an increasingly hard sell.

Look at it this way, if you had an oil-well in your back garden, how much would you be prepared to pay for petrol at the pump?

4 thoughts on “Drive the car, tuppence a mile!

  1. Hi Terence, is there any reason that you don't utilise the Economy 7 tariff? you could reduce the cost to 6p / kWh at night with the daytime cost increased to around 18p (when not using solar).

    1. Only that our supplier doesn't have an E7 tariff, and we don't have an E7 meter. Not sure if the increase in the rest of the bills would be worth the evening savings.

      1. For anyone that does have access to an E7 tariff/meter (and is reading this) I would suggest doing a quick personal calculation. With my nighttime usage now surpassing my day usage (10kWh car charge every night) the saving for me is surprising. If you use more than 40% of your total electricity at night there are overall savings to be had 🙂

  2. Hi. I have a Vauxhall Ampera and soon after buying it swapped to E7 so I could charge it overnight as cheaply as possible. The fitting of the new E7 meter was free with EDF and there was no tie in period. I then swapped to Sainsburys energy , their E7 rate is 5.1 p/unit and daytime rate 12.5p/unit which is actually cheaper than the old EDF rate! So win win. My E7 to normal use is around 50:50. It definitely pays to shop around.

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