Can someone check my math on this? It feels… wrong:

After cycling a little over 8000km on our e-bike, our battery died. Rather inconvenient, but thankfully we had a variety of cycle shops nearby and one of them was able to find us a replacement.

Ours is a Bicicapace Just Long a fantastic cargo bike with a Shimano motor and battery. The battery that we originally purchased with the bike was no longer available, so the replacement battery is a newer model. It is however a legit Shimano battery rather than a cheap knockoff prone to exploding.

The total cost, just for the battery was £600. Interestingly, this is roughly what I paid for my entire road bike about six years ago.

The steep price tag got me thinking though: if all I can expect to get out of this battery is 8000km, what is the “mileage” of my e-bike? Math is not my strong suit, but the number I arrived at is not inspiring:

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If we take the cost of travelling 8000km and ignore the marginal cost of electricity for the sake of my sanity, the cost per kilometre is:

£600 ÷ 8000km  = £0.075/km

That feels… high. My kid’s school is almost 5 kilometres from our home, so every day we take her to school, we’re effectively paying £0.75 for the return trip and again to go pick her up, so £1.50. That’s £7.50/week (not including the weekends which are busier).

Given this, I wondered what it’d cost to do this with a car — only counting the fuel mind you — and the result wasn’t inspiring.

The average milage in the UK for a diesel car is 43MPG. I opted for diesel for this exercise 'cause that’s what it seems like everyone is driving here. Converting this to metric, you get:

1gal → 4.5461L
43mi → 69.2018km

69.2018km ÷ 4.5461L = 15.22 km/L

With this value, we can calculate how many litres of diesel one might use to travel 8000km:

8000km ÷ 15.22km/L = 525.62L

Finally, with the price of diesel currently here in Cambridge hovering at around £1.569/l, that means that the price to pay for the diesel alone for the same distance I travelled on that £600 battery was only a couple hundred bucks more:

1.569 * 525.62 = £824.70

That’s… not inspiring. It’s really hard to convince people that cycling is cheaper when the costs of regular use are so high compared to the ridiculously low cost of fossil fuels. Sure, the electricity cost is negligible, and there are many many other costs associated with cars, but having just bit the bullet on £600 battery after such a short time, let me tell you, that taste is bitter.