Every range, cost, and journey figure on HonestRange is calculated using a single physics model based on each car's measured parameters, not WLTP values or flat percentages. This page details the equations, the constants and their sources, current validation status, and the individual responsible for the model.
Simulink grid
3.33%avg error
9-point grid compared to ANL-validated Simscape model. 8 out of 9 points within 5%.
ANL dyno: Model 3
3.1%avg error
7 laboratory data points, −10 to +27 °C at 65 mph steady cruise.
Operating points
20data points
Across 3 vehicles, using 2 validation methods and real-world temperatures.
The power model is validated against a 9-point grid (30, 50, 70 mph at −5, 10, 20 °C) exported from the author's ANL-validated Simscape/Simulink Tesla Model 3 LR AWD powertrain model (v26, ≤2.2% BMS-net error on UDDS, HWFET, US06, and WLTP drive cycles). The comparison removes the model's HVAC term and normalizes auxiliary load.
3.33%
5.12%
8 of 9
9 of 9
The 5.12% error at 50 mph and 20 °C occurs because the model applies a fixed 90% drivetrain efficiency, while the Simscape model accounts for speed-dependent motor and inverter losses. This is a known structural simplification.
The model is also validated against actual Argonne National Laboratory (ANL) D3 dynamometer measurements, using real current and voltage traces from depletion runs on a chassis dynamometer. Three vehicles were tested at 65 mph steady cruise under real ambient temperatures.
Tesla Model 3 LR AWD
7 data points, −10 to +27 °C. Average error 3.1%, maximum 6.2%. Validation performed at this speed.
Nissan Leaf e+
3 data points, average error 13.6%, maximum 14.2%. Residual error is primarily due to the unmodeled linear road-load term (B=3.18 N·s/m, approximately 2.7 kW at 65 mph).
Chevrolet Bolt EV
4 data points, error range 4–13%. This validation-only vehicle, not sold in the UK, highlights the model's missing linear road-load term.
The model's PTC heater ramp (180 W/°C, 4 kW cap) is supported by measured cabin-heater channel data from the ANL Bolt EV's PTC system. The resulting cold-weather penalty aligns with the Tesla's observed total versus aerodynamic surplus at low ambient temperatures. See fixtures/anl_d3/hvac_findings.md for the full analysis.
The model does not currently include a hot-weather cooling term; approximately 1 kW AC compressor draw measured on the Bolt at 40 °C is not modeled.
The power required to move the car at a steady speed is the sum of four road loads, plus cabin and auxiliary electrical consumption. Speed v is measured in metres per second.
Aerodynamic drag
Paero = ½ · ρ(T) · Cd · A · v³
Rolling resistance
Proll = Crr · m · g · v(×1.1 in rain)
Drivetrain loss
Pdt = (Paero + Proll) · (1/ηdt − 1)
Efficiency
η = vmph / (Ptotal / 1000)mi/kWh
Air density is calculated using the ideal gas law, so colder, denser air reduces range. Cabin heating uses a resistive (PTC) demand of clamp((16 − T) · 180, 0, 4000) watts. A heat pump performs the same function at 45% of that above -5 °C.
State of health follows an exponential approach to a minimum value: SoH = floor + (1 − floor) · e−k·age, with k adjusted so the first-year loss matches the calibrated annual figure for each chemistry and cooling type. Age and mileage are weighted 70/30.
Energy use is integrated for each journey segment; a rapid charge (20→80%, approximated at 75% of the car's peak DC rate) is included before any segment that would drop below 10%. Running cost includes energy + VED + (from 2028/29) 3p/mile, compared to petrol at 40 mpg.
Every constant in the model is sourced. Items marked provisional are modeling assumptions or pending expert review and are not presented as measured facts.
| Constant | Value | Source |
|---|---|---|
| Gravity g | 9.80665 m/s² | CODATA / ISO 80000 standard value |
| Sea-level pressure | 101325 Pa | ISO 2533 Standard Atmosphere |
| Specific gas constant | 287.05 J/(kg·K) | CIPM-2007 dry-air molar mass |
| Rain rolling × | × 1.1 | Wet-road Crr uplift, provisional |
| HVAC setpoint | 16 °C | SPEC §5.1, indoor-comfort reference |
| PTC heater ramp | 180 W/°C, cap 4000 W | ANL Bolt EV PTC heater data |
| Base auxiliary load | 320 W | Modelling assumption, provisional |
| Heat-pump fraction | 45% above -5 °C | Modelling assumption, provisional |
| Preheat HVAC × | × 0.5 | SPEC §5.1, provisional |
| Degradation blend | 70 / 30 | Age/mileage, provisional |
| Annual mileage ref | 8000 mi/yr | DfT National Travel Survey, provisional |
| Journey SoC floor | 10% | Model rule (SPEC §5.3) |
| DC-curve de-rate | × 0.75 | Flat approximation, provisional |
| 2028/29 eVED | 3p/mile | Announced per-mile EV charge |
| EV standard VED | £195/yr | VED reform from 1 April 2025 |
| Default petrol mpg | 40 mpg | SPEC §5.4 user-selectable default |
| UK gallon | 4.54609 L | UK Weights & Measures Act |
| Cost condition | 38 mph, 10 °C, dry | Blended UK urban + A-road, provisional |
Battery degradation profiles: Approximated from the Geotab 2024 fleet study and Nissan Leaf-specific fleet telemetry; provisional and pending author review.
Journey ambient temperature: UK monthly averages (Met Office 1991–2020); a per-location Open-Meteo refinement is planned.
Energy tariffs and pump prices: Indicative UK figures, updated periodically. Each value is individually sourced.
Every figure on each car page is calculated using this model. Explore real range and cost for popular used EVs.
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