How the calculators work
The assumptions and limitations behind myevnumbers results.
Purpose
myevnumbers provides independent planning estimates for UK electric-car drivers. It helps users understand how battery capacity, electricity prices, charging speed, losses, efficiency, mileage and temperature can affect charging cost, time and range.
Core units
- kWh measures energy stored or purchased.
- kW measures charging power.
- mi/kWh measures vehicle efficiency.
- p/kWh is the electricity unit price.
- Fuel comparisons use UK imperial MPG and pence per litre.
Charging energy and cost
Battery energy added is usable battery capacity multiplied by the change in state of charge. Grid energy is higher when charging losses are included. Estimated cost is grid energy multiplied by the selected electricity price. Standing charges are excluded because they are normally paid whether or not the EV is charged.
Charging time
The basic time estimate uses the lower of charger output and vehicle charge-rate limit. The realistic-time tool can apply a slower rate above a chosen battery percentage to illustrate taper. Actual charging curves are vehicle-specific and may also change with battery temperature and charger conditions.
Range
Range is usable battery energy at the selected state of charge multiplied by the chosen miles-per-kWh efficiency. Warm, mild, cool and cold values are editable scenarios, not claims that every EV loses the same percentage of range.
Annual cost comparison
Annual EV energy is based on mileage divided by efficiency, adjusted for home and public charging losses and prices. Petrol or diesel cost uses UK imperial gallons converted to litres. The comparison covers energy or fuel only; it does not include purchase price, depreciation, tax, insurance, servicing or finance.
Limitations
Results are estimates, not vehicle, energy-tariff or journey guarantees. Check the vehicle manual, charger display, network app and tariff terms before relying on a figure. Inputs are deliberately editable so users can replace defaults with their own real-world data.
Privacy by design
Calculations run in the browser. Learn more in Privacy & storage.