I asked AI to solve my commute. It saved me £1,600 a year.

I've been going back and forth on whether to drive to work or take the train. Two days a week, about an hour and forty-five minutes each way. The commute is the same either way. But the cost? I had no idea.

So I asked.

Not Google. Not a comparison site. I just opened a conversation with my AI and typed: "Work out whether driving or taking the train is cheaper. I have a Tesla and an Octopus home charger."

The prompt, in three parts

Work out whether driving or taking the train is cheaper. I have a Tesla and an Octopus home charger.

1. The ask

A clear job to do, not a vague topic.

2. The car

Specific. Not "an EV", a Tesla.

3. The tariff

The detail that made the maths possible.

What happened next is why I started this newsletter.

It didn't give me a generic answer. It went and looked up the actual ticket prices on Trainline for my route. It found parking rates near my office. It asked me one question I hadn't thought about: do you charge at home off-peak or use public chargers? Because that number swings the whole calculation.

I charge at home overnight on Octopus, around 7-8p per kWh.

So it ran the maths.

Train: £35 a day on Anytime returns, plus £6 on the Tube. Around £41 a day. Multiply that by 92 commute days a year and you get £3,220.

Driving: £1.38 in electricity for the round trip at home charging rates. Plus £16 parking. That's £17.38 a day. Annual cost: £1,600.

The gap is £1,620 a year, in favour of driving.

But then it asked me something that changed the whole conversation.

"Do you actually use the commute for anything? Reading, podcasts, thinking time?"

And I was honest. Mostly passive. Phone, music, zoning out. Then it told me about Grok, the AI assistant built into Tesla's software, which arrived in the UK earlier this year. You talk to it while you drive. Ask it questions. Think through problems out loud. It's not the same as writing, but it's not nothing either.

That detail shifted the answer from "probably driving" to "definitely driving." The commute isn't dead time anymore. It's Grok time.

The whole conversation took about ten minutes. The answer would have taken me an hour of tab-switching, rough maths on my phone, and I still probably would have guessed wrong.

What £1,620 a year actually is

In things you can picture.

2

long-haul holidays

flights and a week each

9

months of Claude Pro

at £15 a month, twice over

8

months of groceries

a couple's mid-range shop

1

decent ISA top-up

compounding for years

Here's what you can do right now. Pick any recurring cost you've never properly compared. A subscription, a commute, a weekly shop, an energy tariff. Open Claude, ChatGPT, or whatever you use. Tell it your specific situation. The actual numbers, the actual setup. And ask it to work it out.

The key word is specific. Vague questions get vague answers. The more detail you give, the more useful it becomes.

That's the whole trick. It's not magic. It's just faster than doing it yourself.