I’ll be honest with you. When I first seriously considered switching to an electric car, I thought I had the economics worked out. “Electricity is cheaper than petrol, job done.” Then someone asked me exactly how much cheaper, per mile, and I realised I had absolutely no idea. I knew it was less. I just couldn’t tell you by how much. Given that I now drive a Tesla Model 3, plugged into a wall charger in my driveway every night, that felt like a fairly embarrassing gap in my knowledge.
So I sat down and actually worked it out. The answer, it turns out, is “it depends a lot on your tariff.” Which is either very helpful or deeply annoying depending on how much you like spreadsheets.
What You’re Actually Paying Per Kilowatt-Hour
Before we get to pence per mile, you need to know what you’re paying for electricity in the first place, because this is where most people are fuzzy.
As of April 2026, if you’re on a standard variable tariff under the Ofgem price cap, you’re paying 24.67p per kWh on average across England, Scotland and Wales. That figure dropped from 27.69p in Q1 2026, so there’s been a small but welcome reduction. It’s still not cheap, and it changes every quarter, so don’t tattoo it on your arm.
Economy 7 is the older off-peak tariff that splits your day into two rates. During roughly seven hours overnight (typically 00:30 to 07:30), you pay a lower rate. The current Ofgem average for that night rate is 13.89p per kWh. The day rate on Economy 7 is actually higher than standard variable, sitting around 29.73p per kWh, so the maths only works in your favour if you’re genuinely shifting a lot of usage overnight. The rule of thumb is that 40% or more of your consumption needs to happen in those off-peak hours. Otherwise you might be better off on a flat rate.
Then there’s Octopus Go, which is a different beast entirely. This is a tariff designed around EV drivers. You get a fixed cheap window from 00:30 to 05:30 every night at 8.5p per kWh. Its smarter sibling, Intelligent Octopus Go, works with compatible EVs and chargers to automatically schedule charging when the grid has surplus renewable energy. From April 2026, rates on both tariffs dropped significantly. In many regions, Intelligent Octopus Go night rates fell by around 39%. Here in Hampshire, that means rates dropped from 9p down to 5.49p per kWh for Intelligent Octopus Go, and from 10.5p to 6.99p for standard Octopus Go. Some parts of the country are seeing rates below 4p per kWh. That is genuinely extraordinary.
One thing worth flagging: Octopus recently updated Intelligent Octopus Go so that the super-cheap smart-charging rate now applies for a maximum of six hours per session. If your car needs longer than that to hit its target charge, any time beyond six hours gets billed at the higher “Boost” rate. It’s a significant change from how the tariff used to work, so it’s worth factoring in if you have a larger battery or tend to charge from very low.
Both Octopus EV tariffs require a smart meter. Octopus will install one for free, so that’s not a blocker.
The Pence-Per-Mile Bit (The Part You Actually Wanted)
Right, here’s where it gets concrete. The standard benchmark for EV efficiency is around 3.5 miles per kWh. That’s not a law of physics. It varies depending on your car, how you drive, whether you’re hammering down the motorway or doing school-run stop-start. Heavier SUV-style EVs might do 2.5 to 3 miles per kWh. More aerodynamic models can hit 4-plus. But 3.5 is a fair working number.
Run the numbers across the different tariffs and here’s what you get:
| Tariff | Rate per kWh | Cost per mile (at 3.5 mi/kWh) |
|---|---|---|
| Standard variable (Q2 2026) | 24.67p | ~7.0p/mile |
| Economy 7 night rate | 13.89p | ~4.0p/mile |
| Octopus Go off-peak | 8.5p | ~2.4p/mile |
| Intelligent Octopus Go (Hampshire, April 2026) | 5.49p | ~1.6p/mile |
Now let’s put that up against petrol. The exact comparison depends on current pump prices and your car’s efficiency, but as a rough guide, a reasonably efficient petrol car is going to cost you significantly more per mile than any of those EV figures. Even on the standard variable tariff at around 7p per mile, home-charged electric motoring comes in at comfortably less than half the cost of a typical petrol equivalent. On Intelligent Octopus Go with the new April 2026 Hampshire rates, you’re getting close to 1.6p per mile. That’s not a typo.
How This Actually Plays Out at Home
I charge my Model 3 overnight every night using a Tesla Wall Charger. I’m on a tariff that gives me cheap overnight electricity, and the car is scheduled to charge in the small hours when rates are lowest. I don’t think about it. I wake up, the car is full, and I didn’t stand on a petrol station forecourt in the drizzle.
For a family doing a realistic 10,000 miles a year, here’s what the annual home-charging cost looks like on each tariff, at 3.5 miles per kWh:
- Standard variable: around £700 per year
- Economy 7 (night rate): around £400 per year
- Octopus Go: around £240 per year
- Intelligent Octopus Go (Hampshire, April 2026 rates): around £160 per year
The savings compared to petrol are substantial, particularly on the smarter tariffs. For a working family, that difference adds up fast over a year.
The caveat with Economy 7 is worth repeating. You need to actually use those off-peak hours. If the kids are running the dishwasher at 2pm and the tumble dryer after school, your daytime usage at 29.73p per kWh will eat into those savings fast.
Should You Care About This Right Now?
If you already have an EV, yes, absolutely. Moving to a smart EV tariff like Octopus Go is one of the highest-impact financial decisions you can make. If you’re still on a standard tariff and charging at home, you’re leaving real money on the table every month. If you’re considering an EV and wondering whether the economics actually work, these numbers should give you some confidence. They worked for me.
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If You Want to Have a Go
The simplest entry point is to check whether you have a smart meter. If not, contact your supplier about getting one fitted (Octopus does this for free). From there, compare Octopus Go against your current tariff using their online comparison tool. It takes about ten minutes.
If you want to get more hands-on, a decent home EV charger makes a genuine difference to charging speed and scheduling. My Tesla Wall Charger handles the scheduling automatically, but for other cars a unit like the Ohme Home Pro or Zappi integrates well with smart tariffs.
A plug-in energy monitor is also a cheap way to understand your home’s baseline electricity usage before you commit to any tariff change.
If this kind of breakdown is useful, I write about tech for real family life every week over at the Tech Dads Life newsletter. No fluff, no jargon, just the stuff that actually matters. Come and join us at techdadslife.beehiiv.com and I’ll see you there.
