About the EV Road Trip Calculator
This EV road trip calculator estimates how many fast-charging stops an electric vehicle needs for a long drive, how long you will spend plugged in, what the charging will cost and how long the whole trip takes. Enter the distance, your car's real-world efficiency, usable battery size and the charge you start with, and it works out the energy the trip needs and how it will be supplied.
It is built for EV owners and renters planning a holiday drive, people deciding whether an EV suits their longest trips, and anyone comparing road-trip costs with a petrol or diesel car. The plan follows the way most drivers use DC fast chargers: arrive with a small reserve and charge only to about 80%, where charging is fastest.
Charging power is the average kW you actually receive over a session, which is well below the charger's headline rating because charging slows as the battery fills. Cold weather, high motorway speeds, headwinds and towing can cut efficiency by 20–40%, so lower the efficiency figure for winter or fast driving.
With the default inputs, the charging stops needed is 2. Change any value above to recalculate instantly.
How to use the ev road trip calculator
- 1Enter the trip distance and choose miles or kilometres.
- 2Enter your car’s real-world efficiency and usable battery size.
- 3Set your starting charge, the reserve you want on arrival and the level you charge to.
- 4Enter the average charging power and price per kWh at the chargers on your route.
- 5Read the number of stops, charging time, cost and total trip time.
Formula and method
The trip energy E is the distance divided by efficiency. The first leg uses the battery from the starting charge s down to the arrival reserve r. Any remaining energy must come from charging stops, and each stop can add at most the energy between the reserve and the charge-to level c, so the number of stops is that shortfall divided by the per-stop energy, rounded up.
The calculator assumes the final stop only adds what you need to finish, so the energy bought equals the shortfall. Charging time is that energy divided by the average session power, and cost is the energy divided by (1 − losses) times the price per kWh, because chargers bill for energy that is partly lost as heat. Trip time adds driving time at your average speed.
- E
- Energy needed for the trip (kWh)
- d
- Trip distance
- e
- Efficiency (distance per kWh)
- C
- Usable battery capacity (kWh)
- s, r, c
- Starting charge, arrival reserve and charge-to level (fractions)
- S
- Number of charging stops
- P
- Average charging power (kW)
Worked examples
500-mile trip in a 75 kWh EV
At 3.5 mi/kWh the trip uses 142.9 kWh. Leaving at 90% and arriving at 10% supplies 60 kWh, so 82.9 kWh must be added; each 10–80% stop adds 52.5 kWh, so two stops are needed. At 120 kW that is about 41 minutes of charging, costing about $44.19 after 10% losses.
300 km trip that needs no charging
At 6 km/kWh the trip uses 50 kWh. Starting full with a 10% reserve gives 54 kWh of usable energy, so no stop is needed and the 300 km drive takes about 3 hours 20 minutes at 90 km/h.
1,000 miles in winter with slower chargers
At 2.8 mi/kWh the trip needs 357.1 kWh. The first leg supplies 72 kWh, leaving 285.1 kWh to add; at 56 kWh per 10–80% stop that means 6 stops (the last one short) and about 4.1 hours of charging at 70 kW, costing about $174.
Frequently asked questions
How many charging stops does an EV need on a road trip?+
Divide the trip energy (distance ÷ efficiency) minus what your starting charge provides by the energy each stop adds. A typical 300-mile-range EV charging from 10% to 80% needs a stop roughly every 170–220 highway miles.
Why charge only to 80% on a road trip?+
DC fast charging slows sharply above about 80% to protect the battery, so the last 20% can take as long as the first 60–70%. Two short stops to 80% are usually quicker than one long stop to 100%.
How much does it cost to charge an EV on a road trip?+
Multiply the kWh you add by the charger price. US DC fast charging commonly costs about $0.35–$0.60 per kWh, so an efficient EV often spends around $0.12–$0.18 per mile on the road, less if you charge at home before leaving.
What efficiency should I use for highway driving?+
Use your car’s trip-computer figure at highway speed. Most EVs get 3–4 mi/kWh (about 5–6.5 km/kWh) at 65 mph in mild weather; at 75–80 mph or in freezing weather efficiency can fall to 2.5 mi/kWh or lower.
What is average charging power?+
It is the energy added during a session divided by the session time. Because charging tapers as the battery fills, a car rated for 250 kW might average 100–150 kW from 10% to 80%.