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EV · Calculator

EV Charging Cost Calculator

Work out the cost and time of one charging session at home or at a public charger, each at its own price, then your annual charging cost from an explicit home/public split. Optionally compare a petrol car and estimate emissions.

Pre-filled numbers are example values — replace them with your own. They are not averages for any country.

1. One charging session

Priced only at the location you pick — home and public prices are never averaged here.

Where are you charging?

Example value. Supply-to-battery; varies by car, charger and conditions. Also used for the annual cost.

e.g. 7.4 kW single-phase wallbox, 11 or 22 kW three-phase.

On-board charger limit from the car's specification.

Home (AC) session cost (20% → 80%)

€10.23

40.9 kWh × €0.25/kWh (home price).

Added to battery
36 kWh
Drawn from supply
40.9 kWh

Estimated charge time (AC)

5.5 h

At 7.4 kW — limited by the charger rating.

AC charging is close to constant power for most of a session; some cars slow down in the last few percent.

2. Annual charging cost

Each share is priced at its own tariff. Public session fees are not included.

From your trip computer, battery side.

Public share: 20% (always 100% − home).

Annual charging cost

€982

€6.55 per 100 km · 20.5 kWh/100 km from the supply.

Annual charging split
WhereSharekWhCost
Home80%2,455€614
Public20%614€368
Total100%3,068€982

15000 km ÷ 100 × 18 kWh/100 km = 2,700 kWh into the battery; ÷ 88% efficiency = 3,068 kWh from the supply.

What moves the annual cost

  • All charging at home€767
  • Your mix (80% home)€982
  • All charging public€1,841
  • Home price −10%€920
  • Home price +10%€1,043
  • Efficiency 83%€1,041
  • Efficiency 93%€929

One input changed at a time; everything else stays at your values.

Energy cost vs petrol / year

€578 lower

Petrol €1,560 (975 L) − EV €982. Fuel and electricity only.

How the math works

Energy into battery = battery × (target% − start%)

Energy from supply = energy into battery ÷ efficiency

Session cost = energy from supply × selected location's price (+ public fee)

Effective power = min(charger rating, car's max rate)

Charge time = energy from supply ÷ effective power

Annual supply kWh = km ÷ 100 × consumption ÷ efficiency

Annual cost = home% × kWh × home price + public% × kWh × public price

Worked example with the pre-filled values: 60 kWh × 60% = 36 kWh into the battery; ÷ 0.88 = 40.9 kWh from the supply; at home × 0.25 = 10.23. The 7.4 kW wallbox is below the car's 11 kW AC limit, so time = 40.9 ÷ 7.4 ≈ 5.5 h. If your consumption is in Wh/mi, convert Wh/mi to Wh/km and divide by 10 to get kWh/100 km.

Assumptions. One efficiency figure covers all supply-to-battery losses and is applied to both home and public energy. DC charging time assumes the starting power holds and is an approximation only. No regional prices are built in. Every constant and assumption is listed on the methodology page. To choose a wallbox size from your daily driving, use the home charger sizing calculator.

Frequently asked questions

How is the cost of one charging session calculated?
Energy added to the battery = usable capacity × (target % − start %). Energy drawn from the supply = that energy ÷ charging efficiency. Session cost = supply energy × the price at the location you selected (home or public), plus any public session fee. Home and public prices are never averaged for a single session.
How is the annual cost calculated?
Annual supply energy = distance ÷ 100 × consumption ÷ efficiency. That energy is split by the share you charge at home and the remaining share charged publicly (the two always add to 100%). Each part is priced at its own tariff and the two costs are added. Public session fees are not included in the annual figure.
Why can charging take longer than the estimate?
On AC (home or public posts) the car charges at the lower of the charger rating and its on-board charger limit, which this calculator applies. On DC rapid chargers power changes through the session: it usually falls as the battery fills, and battery temperature and preconditioning matter. No charging curve is modelled here, so the DC time is only an approximation that assumes the starting power holds.
What charging efficiency should I enter?
Wall-to-battery efficiency varies with the car, charger, power level, battery temperature and session length, so there is no single correct figure. The 88% pre-filled is an example only. If your car or charger app reports both the energy delivered and the energy added to the battery, divide the second by the first.
Which electricity prices should I use?
Your own: the unit rate on your home tariff (or the off-peak rate if you charge overnight on a time-of-use tariff) and the per-kWh price at the public chargers you actually use. Prices vary by supplier, contract, country and time, so the calculator does not supply regional averages.
How does the petrol comparison work?
Annual fuel = distance × your petrol car's consumption (L/100 km or mpg), converted to litres. Annual fuel cost = fuel × your pump price. The difference from the EV's annual charging cost is shown. It compares energy costs only — not purchase price, insurance, tax or maintenance.
How are emissions calculated?
Optional. EV: annual charging electricity × the electricity factor you choose (UK 2025 or US eGRID2023, or your own). Petrol: litres × 2.06916 kg CO₂e/L, the UK Government 2025 factor for petrol (average biofuel blend, combustion only). Neither includes fuel or electricity supply chains or vehicle manufacture.

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Charging time & cost guide

The formulas behind this calculator, step by step.

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Monthly charging cost guide

Turn your distance, consumption, losses and tariff into a monthly cost.

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EV vs petrol comparison

What to include beyond energy cost when comparing cars.

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MPG ↔ L/100 km

Convert between US MPG, UK MPG and L/100 km.

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Home Charger Sizing

Check what wallbox power your daily driving actually needs.

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Methodology

Every formula, constant and assumption used across the tools.