Eight pence a kilowatt-hour at home looks almost trivial until you put it next to what motorway rapid chargers actually bill. The RAC’s Charge Watch snapshot from July 2024 put the average UK rapid DC rate at 75p/kWh — nearly ten times an overnight home rate of 8p. For a driver covering about 12,000 miles a year, that gap is not a rounding error. It is the difference between a modest monthly energy bill and something that starts to feel like old-school petrol money again.
Most of the “EVs are cheap to run” conversation still skates over where the electricity comes from. Home off-peak, flat-rate household power and public rapid are three different products at wildly different prices, and in 2026 that split is still the single biggest lever on what a UK EV actually costs to run — bigger than badge, bigger than battery size. What follows is an inspectable monthly energy-cost model, and every pence figure in it is a published July 2024 rate: rates in, pounds out. Treat those figures as a worked baseline, not gospel, because the Ofgem cap, the EV tariffs and the RAC’s rapid average all move every price-cap quarter. The discipline is simple: drop today’s numbers from the linked sources into the same arithmetic before you bank on any total. The structure is what lasts. The inputs are what you refresh.
July 2024 tariffs on a Tesla Model Y home-charge night vs public rapid
Three established home EV products sat in a tight overnight band. Octopus Intelligent Go listed 7.5p/kWh in a typical six-hour overnight window (23:30–05:30), with a peak rate of 30.5p/kWh. OVO Charge Anytime marketed scheduled sessions at an effective 7p/kWh, against a standard household unit of 28.6p. EDF GoElectric put off-peak EV charging at 8p/kWh across a seven-hour night window, with a day rate of 32p.
The flat-rate comparator is the Ofgem July–September 2024 price cap standard variable unit at 28.6p/kWh — what many drivers still pay if they never switch to an EV-friendly overnight product. On the public side, the RAC’s 75p/kWh average sat between Tesla Supercharger pay-as-you-go around 55p, Ionity motorway sites around 69p, and Gridserve ultra-rapid hubs around 79p. I use the RAC average as the single public-rapid line: the sober midpoint of a mixed UK motorway diet.
At 1,000 miles a month, shifting the same energy from 8p home off-peak to 75p public rapid multiplies the pure electricity bill by almost ten.
Tesla Model Y efficiency bands for a 1,000-mile month
Real-world mi/kWh swing with weather, speed and load. The model prices three fixed bands for 1,000 miles a month (12,000 a year, level-loaded): 3.0 mi/kWh for heavier cars and cold motorway months; 3.5 mi/kWh as a mixed-UK middle; 4.0 mi/kWh for a lighter right foot and warmer weather. Energy is miles ÷ efficiency: 333.3, 285.7 and 250.0 kWh. Cost is energy × unit rate.
Those bands sit close to WLTP-derived figures for three premium daily drivers: Tesla Model Y RWD at about 4.1 mi/kWh on a 60 kWh usable pack, BMW iX3 at about 3.9 mi/kWh on 74 kWh, and Porsche Macan Electric (Macan 4 framing) at about 3.4 mi/kWh on 95 kWh. Bands first; named packs later for annual totals.
Worked calculation for Tesla Model Y and BMW iX3 energy cost
Inputs (July 2024 published rates)
- Monthly distance: 1,000 miles (12,000 miles/year)
- Efficiency bands: 3.0 / 3.5 / 4.0 mi/kWh
- Home off-peak sample: Octopus Intelligent Go 7.5p/kWh; OVO Charge Anytime effective 7p/kWh; EDF GoElectric 8p/kWh
- Flat-rate home: Ofgem SVT unit 28.6p/kWh
- Public rapid average: RAC Charge Watch 75p/kWh
- Named-model WLTP-derived efficiency / usable pack: Model Y RWD 4.1 mi/kWh / 60 kWh; BMW iX3 3.9 mi/kWh / 74 kWh; Porsche Macan Electric 3.4 mi/kWh / 95 kWh
Method and assumptions: 100% of monthly energy at a single unit rate (pure scenario lines); no standing charges, connection fees, idle penalties or membership discounts; no home-charger amortisation; level monthly miles.
Step 1 — kWh per 1,000-mile month
3.0 mi/kWh → 1,000 ÷ 3.0 = 333.3 kWh 3.5 mi/kWh → 1,000 ÷ 3.5 = 285.7 kWh 4.0 mi/kWh → 1,000 ÷ 4.0 = 250.0 kWh
Step 2 — monthly cost (£) = kWh × (p/kWh ÷ 100)
| Rate | 3.0 mi/kWh | 3.5 mi/kWh | 4.0 mi/kWh |
|---|---|---|---|
| OVO effective 7p | £23.33 | £20.00 | £17.50 |
| Octopus off-peak 7.5p | £25.00 | £21.43 | £18.75 |
| EDF off-peak 8p | £26.67 | £22.86 | £20.00 |
| Flat home 28.6p | £95.33 | £81.71 | £71.50 |
| Public rapid 75p | £250.00 | £214.29 | £187.50 |
Step 3 — annual totals (£) = monthly × 12
| Rate | 3.0 mi/kWh | 3.5 mi/kWh | 4.0 mi/kWh |
|---|---|---|---|
| OVO 7p | £280 | £240 | £210 |
| Octopus 7.5p | £300 | £257 | £225 |
| EDF 8p | £320 | £274 | £240 |
| Flat 28.6p | £1,144 | £981 | £858 |
| Public 75p | £3,000 | £2,571 | £2,250 |
Step 4 — named models at WLTP-derived efficiency, 12,000 miles/year
Model Y (4.1 mi/kWh): 12,000 ÷ 4.1 = 2,927 kWh/year @ 7.5p home → £220 @ 8p home → £234 @ 28.6p flat → £837 @ 75p public → £2,195 BMW iX3 (3.9 mi/kWh): 12,000 ÷ 3.9 = 3,077 kWh/year @ 7.5p home → £231 @ 8p home → £246 @ 28.6p flat → £880 @ 75p public → £2,308 Macan Electric (3.4 mi/kWh): 12,000 ÷ 3.4 = 3,529 kWh/year @ 7.5p home → £265 @ 8p home → £282 @ 28.6p flat → £1,009 @ 75p public → £2,647
Outputs that matter: at 3.5 mi/kWh, pure public-rapid energy is about £2,571/year versus roughly £257–£274 on 7.5–8p home off-peak — near tenfold. Flat home at 28.6p (£981/year at 3.5) still undercuts all-public rapid by more than £1,500. Cost-per-mile at 7.5p home: about 2.5p at 3.0 mi/kWh and 1.9p at 4.0; at 75p public: about 25p and 18.8p per mile.
Why £0.08/kWh still holds for a Tesla Model Y daily driver
EDF’s published 8p night rate is the cleanest match for the headline comparison; Octopus at 7.5p and OVO’s effective 7p only strengthen the home side. On a 1,000-mile month at 3.5 mi/kWh, 8p home is £22.86; the same energy on the RAC’s 75p average is £214.29. Unit arithmetic, not marketing. The pence figures will drift with each price-cap quarter, but the ratio between an overnight product and a motorway rapid rarely narrows enough to change the call.
Treating rapid as a lifestyle default rather than a tool is where people lose the plot. A long motorway day on Ionity or Gridserve pricing is rational; building every midweek top-up around 75p average DC is how a premium EV starts to feel oddly expensive. The wallbox decision sits next door — see the best home EV charger choices in 2026.
BMW iX3, Tesla Model Y and Porsche Macan Electric named packs
Battery size does not rewrite the unit-rate story; efficiency does. On pure public rapid at 12,000 miles, the Macan’s 3.4 mi/kWh line is about £2,647 a year against roughly £2,195 for the Model Y at 4.1 — same RAC rate, different thirst. On 8p home, both stay inside a few hundred pounds. Pack size matters for range; efficiency prints on the bill. These annuals are energy-only — no standing charges, charger hardware or company-car tax framing (see the fuel benefit versus EV charging benefit gap for 2026/27).
The quiet failure mode is flat-rate home power. At 28.6p, a 3.5 mi/kWh year is about £981 — still far below all-public rapid, but three to four times an overnight EV tariff. Broader context: EV running costs in 2026: home charging versus public prices; this model is the calculator layer.
Three leaks still matter. Peak-hour home top-ups (Octopus 30.5p peak, EDF 32p day) erase most of the overnight gift. Unplanned motorway sessions as the weekly norm push the annual line toward £2,000–£2,500. Brochure mi/kWh in January is fiction: drop from 4.0 to 3.0 and monthly home off-peak rises by roughly a third; at 75p public, £187.50 becomes £250 for the same 1,000-mile month.
Where this leaves a premium EV’s running-cost case
If most of a 12,000-mile year can live on a 7–8p overnight home product, pure energy cost for a premium EV sits in the low hundreds of pounds on these July 2024 rates — Model Y territory around £220–£234 at brochure-leaning efficiency, Macan still under £300 on 8p. That is the driveway case, without romance.
If life is public-rapid first — no reliable overnight access, heavy motorway weeks — price energy closer to £2,200–£2,650 a year on this mileage, using the RAC’s 75p average as the midpoint. That does not make the car irrational. It does mean “pennies per mile” stops being your friend, and residual value, BiK and finance must carry more of the case.
My position is blunt: for a UK driver with off-street parking, the 8p-class home night rate is what makes a premium EV’s running-cost story honest; public rapid is the safety net and the long-trip tool, not the default fuel. Run your own miles, at today’s tariff and rapid rates, through the tables. If most of your kilowatt-hours cannot live on the overnight line, recalculate at the current public rate before you sign — not after the first quarterly statement surprises you.
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Use this as the final check before paying a deposit, signing finance paperwork or relying on a headline monthly figure.
