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Home / Converters / EV Efficiency Converter (Wh/km, kWh/100km, mi/kWh, MPGe)

EV Efficiency Converter (Wh/km, kWh/100km, mi/kWh, MPGe)

Convert electric vehicle efficiency between Wh/km, kWh/100km, mi/kWh and MPGe. Estimate range and charging cost.

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Frequently asked questions

Is my data sent to a server?
No. All conversions and estimates are calculated entirely in your browser using JavaScript. No vehicle data, battery size, or electricity cost figures are ever sent to any server. The tool works offline once the page has loaded.
What formulas are used?
1 kWh/100km = 10 Wh/km (exact). mi/kWh = 62.1371 ÷ kWh/100km (using 1 mile = 1.60934 km). MPGe = mi/kWh × 33.7 (EPA standard: 1 US gallon = 33.7 kWh of electrical energy equivalent). Range (km) = Battery capacity (kWh) ÷ (kWh/100km ÷ 100). Charging cost = (distance ÷ 100) × kWh/100km × electricity price per kWh.
How does EV efficiency compare to a petrol car?
EVs are dramatically more efficient in energy conversion terms. A typical EV uses about 15–20 kWh per 100km, equivalent to roughly 1.5–2 litres of petrol in energy content. A typical petrol car uses 6–10 litres per 100km. Because electricity is also much cheaper per kWh of energy than petrol, the cost-per-kilometre of running an EV is usually 3–5 times lower than an equivalent petrol vehicle in most European countries.
What is MPGe and why does the US use it?
MPGe — Miles Per Gallon equivalent — was introduced by the US EPA in 2011 to give American consumers a familiar reference point for EV efficiency. The conversion factor is 33.7 kWh = 1 US gallon of gasoline (in energy content). A car rated at 100 MPGe uses 33.7 kWh of electricity per 100 miles, which is the energy equivalent of driving 100 miles on one gallon of petrol. The metric is useful for comparison but does not account for the higher efficiency of electric drivetrains.
What is a limitation of these efficiency figures?
Official efficiency ratings (WLTP in Europe, EPA in the US) are measured under controlled laboratory conditions. Real-world consumption depends heavily on driving speed (motorway driving at 130 km/h can increase consumption by 40–60% vs city driving), ambient temperature (cold weather reduces battery capacity and increases cabin heating demand), load, and driving style. Always treat official figures as optimistic baselines and plan trips with a conservative real-world estimate.
What does a kWh/100km figure actually mean in practice?
It tells you how many kilowatt-hours of electricity your car draws from the battery for every 100 kilometres driven. A car rated at 16 kWh/100km with a 64 kWh battery has a theoretical range of 400 km. In practice, you would typically plan for 75–80% of that (300–320 km) to account for real-world conditions and to avoid depleting the battery fully, which accelerates degradation.
I am new to EVs — why does range vary so much in different conditions?
Two main factors: speed and temperature. Aerodynamic drag increases with the square of speed, so driving at 130 km/h uses roughly twice the energy per kilometre as driving at 90 km/h. Cold weather reduces the battery's usable capacity (lithium-ion batteries lose efficiency below 10°C) and adds energy demand for cabin heating, especially in cars without heat pumps. A range of 400 km on a mild day might drop to 280 km in freezing conditions at motorway speed.
Can I use this calculator for fleet management or professional EV analysis?
Yes. Fleet managers frequently need to compare vehicles reported in different efficiency standards, estimate charging infrastructure requirements, and model total cost of ownership across vehicle types. This tool handles the unit conversions and basic range/cost estimates. For full TCO analysis including depreciation, maintenance, and tax incentives, a dedicated fleet management platform would be more appropriate.
What is a common mistake when estimating EV range?
Taking the official WLTP or EPA range as a guaranteed figure. These tests are conducted at moderate speeds (typically averaging 46 km/h for WLTP), in moderate temperatures, with no passengers or cargo, and with climate control off. Real-world range on a cold winter motorway journey can be 30–40% less than the WLTP figure. Always apply a conservative buffer and plan charging stops on long routes.
Does efficiency change depending on the country's electricity mix?
The efficiency of the car itself does not change, but the carbon footprint per kilometre does. In countries with a high share of renewable electricity (e.g., Norway, Iceland), an EV's lifecycle emissions are extremely low. In countries with a coal-heavy grid, an EV may have only a modest carbon advantage over a modern petrol hybrid in lifecycle terms. For running cost calculations, use your local electricity tariff, which varies from roughly €0.08/kWh (off-peak in some markets) to over €0.35/kWh in countries with high energy taxes.

About EV Efficiency Converter (Wh/km, kWh/100km, mi/kWh, MPGe)

Electric vehicle efficiency describes how much electrical energy a car consumes to travel a given distance, and it is reported in strikingly different ways depending on where you are in the world. In Europe, most manufacturers and regulators use kilowatt-hours per 100 kilometres (kWh/100km) or watt-hours per kilometre (Wh/km) — both "lower is better" metrics analogous to litres per 100km for petrol cars. In the United States, the EPA reports efficiency as miles per kilowatt-hour (mi/kWh, higher is better) and also as MPGe — Miles Per Gallon equivalent — a unit that converts electrical energy consumption to an equivalent volume of gasoline using the energy equivalence of 33.7 kWh per US gallon. This figure was chosen because a US gallon of gasoline contains approximately 132 megajoules of energy, and 33.7 kWh is the electrical equivalent. Understanding these units and how they relate to each other is essential for making meaningful comparisons between EVs from different markets, or for comparing an EV with a conventional internal combustion engine vehicle on a like-for-like basis.

This converter is useful whenever you need to cross-reference an EV's efficiency specification across different standards. Common scenarios include comparing a European car spec sheet (kWh/100km) with a US EPA rating (MPGe), calculating the real-world range from a stated battery capacity and efficiency figure, estimating how much a road trip will cost in electricity, or comparing the running cost of an EV against a petrol car. The efficiency advantage of EVs over ICE vehicles is substantial: a typical modern EV converts 85–90% of battery energy to motion, whereas a petrol engine converts only 20–40% of the fuel's energy — the rest is lost as heat.

All conversions run locally in your browser — no data is transmitted to any server. Enter a value in any efficiency unit and the others update automatically. The range estimate divides your stated battery capacity by the efficiency figure. The charging cost estimate multiplies the energy consumed by your local electricity tariff per kWh. All formulas are exact: 1 kWh/100km = 10 Wh/km; MPGe = (mi/kWh) × 33.7; mi/kWh = 100 ÷ (kWh/100km × 1.60934).

When interpreting results, keep in mind that real-world range is typically 10–25% lower than official test-cycle figures due to motorway speeds, cold weather, climate control use, and driving style. Battery degradation over time also reduces range. For long-trip planning, always budget for a meaningful buffer below the rated range. These results are for informational and planning purposes only.

From Milk Floats to Gigafactories: The Surprisingly Long History of Electric Vehicles

Electric vehicles are often presented as a 21st-century invention, but they predate the internal combustion engine. Scottish inventor Robert Anderson built one of the first crude electric carriages in the 1830s, and by the 1880s and 1890s, practical electric vehicles were commercially available. Around 1900, electric cars outsold petrol cars in the United States. They were quieter, easier to start (petrol cars required a dangerous hand crank), and more reliable for short urban journeys. In 1899, a Belgian EV called "La Jamais Contente" ("The Never Satisfied") became the first land vehicle to break the 100 km/h barrier, driven by Camille Jenatzy.

The rise of cheap Texas oil, Charles Kettering's 1912 invention of the electric starter motor for petrol cars, and Henry Ford's mass-production Model T combined to essentially kill the early EV market by the 1920s. Electric vehicles survived in niche roles — milk floats in the UK, golf carts, fork lifts — but were absent from mainstream roads for most of the 20th century. The 1970s oil crisis sparked renewed interest, and California's Zero Emission Vehicle mandate in 1990 led to the General Motors EV1, a widely admired but ultimately discontinued car whose story was later told in the documentary "Who Killed the Electric Car?"

The modern EV era dates to 2008–2010, with Tesla's Roadster demonstrating that lithium-ion battery technology could deliver genuine performance and range. The Nissan Leaf, launched in 2010, became the first mass-market battery EV. Since then, battery energy density has improved by roughly 85% while costs have fallen by over 90% per kWh — from approximately $1,100/kWh in 2010 to under $100/kWh by the mid-2020s. The efficiency metric kWh/100km has become the European standard partly because it mirrors the familiar L/100km fuel consumption figure, making it intuitive for drivers switching from petrol cars.

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