Continue from the EV range estimate
Translate range into a route plan, understand the charging-time boundary and calculate the energy cost of the journey without planning to the theoretical minimum.
Can the planned trip finish above reserve?
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What this electric-car range calculator estimates
The calculator estimates an energy balance, not an official certified range. It starts with the usable battery energy between current charge and a chosen reserve, then divides that energy by adjusted battery-side consumption.
A planned trip adds another check: energy required for the route, expected arrival state of charge and distance margin. The result is useful for scenarios, purchase research and classroom work, but it does not receive live elevation, traffic, weather or battery data from the car.
Use recent consumption from a similar route whenever available. A test-cycle figure and a winter motorway journey answer different questions.
EV range formula with state of charge and reserve
The same formula calculates full-charge range by replacing current SoC with 100%. Reserve energy remains in the battery and is not counted as planned driving energy.
If current charge does not exceed the chosen reserve, there is no positive planned range window. The calculator asks for a higher starting charge or a lower reserve.
Gross battery capacity versus usable capacity
Gross or nominal capacity describes the battery pack’s total stated energy. The battery-management system normally protects buffers that are not fully available to the driver. Usable or net capacity is the better direct input for range.
If only gross capacity is known, multiply it by a documented usable percentage. Do not subtract the trip reserve from capacity as well: the calculator already applies reserve through the SoC window.
Battery health can be represented by a lower current usable capacity. Avoid applying both a reduced usable capacity and a second undocumented degradation penalty.
Understanding kWh/100 km, kWh/100 mi and distance per kWh
| Entered unit | Meaning | Conversion to kWh/100 km |
|---|---|---|
| kWh/100 km | Energy used over 100 kilometres | Use directly |
| kWh/100 mi | Energy used over 100 miles | Divide by 1.609344 |
| mi/kWh | Miles travelled per kWh | 62.1371 ÷ mi/kWh |
| km/kWh | Kilometres travelled per kWh | 100 ÷ km/kWh |
Consumption must be battery-side. Grid energy used to recharge includes charging losses and belongs to the charging-cost calculation, not the driving-range denominator.
Weather, speed, terrain and wind adjustments
Temperature can affect battery behaviour and the need for cabin conditioning. Speed changes aerodynamic demand, while elevation, headwind, wet roads, tyre pressure, payload and driving style can move route consumption.
The two percentage fields make those assumptions explicit. Positive values increase traction consumption; negative values model favourable conditions. They are added before the auxiliary load is included.
Do not enter a winter value measured on the same route and then add the full winter effect again. Use either an already representative observation with small adjustment or a neutral base with documented changes.
Heating and air-conditioning as an auxiliary kW load
A constant auxiliary device consumes energy with time. The calculator converts average auxiliary power into distance consumption:
At 1.2 kW and 80 km/h, auxiliary demand adds 1.5 kWh/100 km. At the same power but 30 km/h it adds 4 kWh/100 km because covering 100 km takes longer.
Average auxiliary power is not the appliance’s peak rating. Use a route average that accounts for cycling and preconditioning where relevant.
Consumption sensitivity and remaining range
This table applies −10%, the entered adjusted consumption and +10% while keeping battery energy and reserve unchanged.
| Scenario | Consumption | Range to reserve | Trip energy | Arrival SoC |
|---|---|---|---|---|
| — | ||||
Range available at different charge levels
The reserve and adjusted consumption stay fixed. The table shows how the energy window changes at common charge levels and at the entered current charge.
| Starting charge | Energy to reserve | Range in km | Range in miles |
|---|---|---|---|
| — | |||
Arrival SoC and trip margin
Trip energy equals adjusted consumption multiplied by route kilometres. Dividing that energy by usable capacity converts it into battery percentage. Expected arrival SoC is starting SoC minus this percentage.
A positive distance margin means the route ends before the chosen reserve is reached. A negative margin is the extra distance beyond the planned energy window. Conditions can change during travel, so a small positive result is not the same as a robust route plan.
For an actual long journey, confirm the car’s route planner, charging stops, station availability and a contingency option.
Where to get reliable inputs
| Input | Preferred source | Check |
|---|---|---|
| Usable capacity | Manufacturer technical data or a well-documented vehicle database | Do not confuse gross and usable kWh |
| Current SoC | Vehicle display or app | Use the value close to departure |
| Consumption | Long-term display or a comparable completed route | Confirm battery-side boundary and unit |
| Condition change | Your warm/cold and urban/highway history | Avoid duplicating effects already in measured consumption |
| Auxiliary power | Vehicle energy screen or documented equipment estimate | Use average, not peak power |
| Average speed | Navigation estimate or prior journey | Elapsed average differs from speed-limit value |
Build an expected, cautious and stress-test range case
A single estimate can hide how sensitive the trip is to its inputs. Begin with an expected case based on recent consumption from comparable driving. Create a cautious case by increasing consumption or the weather and route adjustments, while leaving battery capacity and starting charge unchanged. A stress test can combine a lower starting charge, stronger auxiliary demand and an intentionally larger reserve.
Compare arrival SoC and trip margin across all three cases. If the expected case works but the cautious case crosses the reserve, the practical decision is not simply “go” or “do not go.” It may be to precondition while plugged in, start with more charge, reduce sustained speed or identify an earlier charging stop.
Keep every adjustment traceable. Changing several inputs without recording why makes the result difficult to repeat and can disguise double counting.
Turn a certification range into a route-specific assumption
A published test-cycle range is useful for comparing vehicles under the same procedure, but it does not directly reveal the consumption for today’s route. If usable capacity and certified range are both known, an implied test consumption can be approximated by dividing usable kWh by range and multiplying by 100. Treat that as a reference point rather than a measured trip value.
For a route estimate, a recent vehicle consumption figure is normally more informative. Match motorway with motorway, winter with winter and a loaded vehicle with a similar payload. Then use the explicit adjustment fields only for differences not already represented in that observation.
This approach prevents two common errors: assuming the certification number is a promise, and applying the same weather or speed effect once in the observed consumption and again as a percentage uplift.
Worked example: 75 kWh battery and a 200 km trip
An EV has 75 kWh usable capacity, starts at 80% and keeps 10% reserve. Base consumption is 18 kWh/100 km. Conditions add 0%, average auxiliary load is 1.2 kW and average speed is 80 km/h. The trip is 200 km.
- Energy to reserve = 75 × (80% − 10%) = 52.5 kWh.
- Auxiliary demand = 1.2 ÷ 80 × 100 = 1.5 kWh/100 km.
- Adjusted consumption = 18 + 1.5 = 19.5 kWh/100 km.
- Range to reserve = 52.5 ÷ 19.5 × 100 = 269.23 km.
- Trip energy = 200 × 19.5 ÷ 100 = 39 kWh.
- Arrival SoC = 80% − 39 ÷ 75 × 100 = 28%; margin to reserve is about 69.23 km.
Exercise for automotive and electric-vehicle students
A delivery EV has 60 kWh usable capacity and starts at 90% with a 15% reserve. Base consumption is 20 kWh/100 km. Cold weather adds 20%, route conditions add 10%, auxiliaries average 2 kW and average speed is 50 km/h. Find adjusted consumption and range to reserve.
- Traction adjustment = 20 × [1 + (20% + 10%)] = 26 kWh/100 km.
- Auxiliary demand = 2 ÷ 50 × 100 = 4 kWh/100 km.
- Total adjusted consumption = 30 kWh/100 km.
- Available energy = 60 × (90% − 15%) = 45 kWh.
- Range = 45 ÷ 30 × 100 = 150 km.
- The reserve stores 60 × 15% = 9 kWh and is not included in the 150 km window.
Common EV range calculation errors
- Using gross battery capacity as fully driveable energy.
- Subtracting hidden battery buffers twice.
- Using grid kWh with charging losses as battery driving consumption.
- Mixing kWh/100 miles with kWh/100 kilometres.
- Entering mi/kWh as if a larger number meant higher consumption.
- Applying a weather penalty to a consumption figure already measured in the same weather.
- Using peak heater power as a whole-trip average.
- Ignoring reserve or treating 0% displayed charge as a routine target.
- Calling a small calculated margin a guaranteed arrival buffer.
Assumptions, limitations and the next calculator
The model holds consumption and auxiliary power constant over the route. It does not simulate elevation segments, regenerative-braking limits, traffic, battery temperature, thermal preconditioning, precipitation, tyre changes, payload changes, battery power limits or charging stops. The vehicle’s displayed SoC and usable capacity can also contain estimation uncertainty.
Run a higher-consumption case and keep a practical contingency beyond the mathematical reserve. For live travel, use current vehicle and navigation information.
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