I recently ran the numbers to decide whether switching to a Tesla Model 3 made sense for my city life. I wanted more than headlines or broad statements — I wanted exact calculations, hidden costs surfaced, and a realistic per-kilometre figure I could rely on. If you’re weighing an electric Tesla against a petrol car for urban driving, here’s the method I used and the figures I got for a clear, actionable comparison.
My assumptions (so you can adapt them)
Any sensible comparison starts by agreeing on assumptions. Here’s what I used — change them to match your city, mileage, or local prices:
Annual mileage: 12,000 km (typical city commuter)Driving mix: Mostly urban, stop-start traffic (benefits EVs)Tesla Model 3 Long Range purchase price: £45,000 (including on-road costs)Petrol car example: compact hatchback similar to Toyota Corolla or Volkswagen Golf — purchase price £25,000Electric consumption (real-world city): 15 kWh/100 kmCharging efficiency & losses: 90% usable (i.e., you pay for 1/0.9 of consumed energy)Home electricity price: £0.20/kWh (off-peak or average)Public rapid charging: £0.45/kWh (occasional use)Average electricity mix used: 80% home charging, 20% public fastPetrol consumption (city combined): 7 L/100 kmPetrol price: £1.60/LHome charger installation: one-time £1,000 (EVSE + install)Annual insurance: Tesla £1,200; petrol car £900Maintenance/servicing: Tesla £300/year; petrol car £700/yearTire/brake wear: Tesla slightly higher tyre wear, estimate +£50/year compared to petrolVehicle excise duty (road tax): Tesla £0; petrol car £165/year (example)Depreciation (approximate average): Tesla 25% in first 3 years; petrol 35% in first 3 years — I translate this into annual averages belowULEZ/congestion charges (if applicable): Tesla £0 per day; petrol car £15/day when driving inside zones (I include a city-specific annual estimate later)Energy/feedstock cost: per-kilometre maths
Start with the basics: what it costs to move the car a kilometre.
Tesla Model 3 (city):
Energy use: 15 kWh / 100 km = 0.15 kWh/kmAccounting for charging losses: 0.15 / 0.9 = 0.167 kWh/km paid forWeighted electricity cost: (0.8 * £0.20) + (0.2 * £0.45) = £0.26/kWh averageCost per km = 0.167 kWh/km * £0.26/kWh = £0.0434/km (≈ 4.34p/km)Petrol car:
Fuel use: 7 L / 100 km = 0.07 L/kmCost per km = 0.07 L/km * £1.60/L = £0.112/km (≈ 11.2p/km)At this point, purely for fuel/electric energy, the Model 3 is ~£0.0686 cheaper per km. Over 12,000 km that's about £823 saved annually on “fuel”.
Charging hardware and upfront extras (amortised)
EVs come with upfront extras: home charger installation and occasionally adaptors or wallboxes. I amortised the cost over five years.
Home charger install: £1,000 / 5 years = £200/yearAdded to per-km: £200 / 12,000 km = £0.0167/km (≈ 1.67p/km)This raises the Model 3’s per-km energy-and-install cost to about £0.060/km — still cheaper than petrol’s £0.112/km.
Maintenance, insurance, and taxes
EVs save on mechanical servicing but can have higher insurance or tyre costs. Here’s how I put numbers to it.
Tesla insurance: £1,200/yearPetrol insurance: £900/yearTesla maintenance: £300/yearPetrol maintenance: £700/yearTesla tyres/brakes extra cost: +£50/yearRoad tax: Tesla £0, Petrol £165/yearNet annual ongoing costs (insurance + maintenance + tax):
Tesla: £1,200 + £300 + £0 + £50 = £1,550/yearPetrol: £900 + £700 + £165 = £1,765/yearThat puts Tesla slightly cheaper annually by about £215 in ongoing fixed costs.
Depreciation — the big hidden cost
Depreciation is often the largest lifetime cost and depends on initial price and resale. I used conservative annualised figures.
Tesla purchase £45,000. If it loses 25% over 3 years, that's ~£11,250 / 3 = £3,750/year or ~£0.3125/km over 12,000 km.Petrol purchase £25,000. If it loses 35% over 3 years, that's ~£8,750 / 3 = £2,917/year or ~£0.2431/km over 12,000 km.So the Tesla costs ~7p/km more in depreciation under these assumptions — a major driver of total cost.
Other city-specific costs and savings
City driving introduces unique factors:
ULEZ/congestion/clean-air charges: If your petrol car faces daily charges (for example, £15/day in central zones), this can quickly flip economics in favour of EVs. For someone commuting into a zone 200 work days/year, that's £3,000/year saved by driving an EV.Parking discounts: many councils offer EV discounts or free parking — monetise these if they apply.Home vs curb charging: If you can’t install a home charger and rely on expensive public charging, EV economics worsen. A switch from 80/20 home/public to 50/50 increases the Tesla’s per-km electricity cost: new avg kWh price = (0.5*0.20 + 0.5*0.45) = £0.325/kWh → cost/km becomes ~0.167*0.325 = £0.0543/km plus install amortised (if you paid it but can’t use). If you cannot install, include public-only assumptions and omit the installation amortisation.Battery degradation/replacement: current data suggests most Model 3 batteries last many years. I didn’t include a full battery replacement cost in annual figures, but factor it in if you plan to keep the car 10+ years or drive very high mileage.Annual cost summary table (approximate)
| Tesla Model 3 (annual) | Petrol car (annual) |
|---|
| Energy / fuel | £(0.0434/km * 12,000) = £521 | £(0.112/km * 12,000) = £1,344 |
| Home charger amortised | £200 | £0 |
| Insurance + maintenance + tax | £1,550 | £1,765 |
| Depreciation (annualised) | £3,750 | £2,917 |
| Extra tyres/consumables | £50 | £0 |
| Total annual cost | £6,071 | £5, ,?* see note below |
Note: The table above is illustrative — total for petrol shown is £6,026 (1,344 + 0 + 1,765 + 2,917 = £6,026). Tesla total ~£6,071. Under these baseline inputs, the cars are nearly equal in annual cost, with the petrol car slightly cheaper by ~£45/year. But small changes change the outcome dramatically.
What flips the result in city driving?
In my calculation, the main reason the petrol car looks marginally cheaper is the higher upfront price (and thus depreciation) of the Tesla. But several common city factors can rapidly swing things in favour of EVs:
If you drive into low-emission zones frequently and avoid charges (e.g., ULEZ), EVs save thousands annually.If your electricity tariff is cheaper (overnight off-peak rates, or solar panels on your roof), the Model 3’s per-km cost drops further.If petrol price rises (it’s volatile), the petrol running cost goes up; EVs are insulated from oil shocks.If you plan to keep the car longer than three years, depreciation dynamics can change — EV resale can improve depending on market demand and battery health.How I’d customise this to your situation
Do this simple spreadsheet exercise with your numbers:
Enter your purchase prices, local electricity and petrol costs, and your true annual km.Decide what share of charging is home vs public. If you have home charging and cheap night rates, that benefits EVs dramatically.Estimate any city charges you avoid by owning an EV and add any parking perks.Think about how long you’ll keep the car — depreciation matters most early on.Once I plugged in my real commute and the fact I often enter a low-emission zone, the Model 3 tilted from marginally more expensive to clearly cheaper within two years. If you live where ULEZ-like charges apply, or you have reliable access to home charging, EVs will often win the city race — not just on emissions, but on your wallet.
Final practical tips
If you can, install a smart home charger and switch to a dedicated EV tariff — even small kWh savings matter over years.Factor in resale demand in your region; certain years and spec (long range, FSD?) can change depreciation notably.When test-driving, check tyre sizes — larger rims common on EVs increase replacement costs.Look for local incentives: grants, reduced parking, or workplace charging can materially affect costs.If you want, I can run the same calculations with your exact numbers — purchase prices, annual km, and the % of charging at home vs public — and produce a personalised per-kilometre and annual-cost comparison you can rely on. Send me your inputs and I’ll do the maths.
