How CLTC EV Range Is Calculated

CLTC range is often dismissed with a conversion percentage, but that shortcut hides the reason the number differs. China’s procedure uses a distinct speed distribution and a regulated battery-depletion method, so its bias relative to another cycle depends on the vehicle.

Two standards form the core

GB/T 38146.1-2019 defines the China Automotive Test Cycle for light-duty vehicles. GB/T 18386.1-2021 defines how a light-duty electric vehicle’s energy consumption and driving range are tested and calculated. The latter standard is current and has received a later amendment. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

CLTC is therefore not merely an advertising multiplier. The drive trace, road load, battery preparation, test termination, measurement and calculation rules all belong to the certified result.

There are two relevant light-vehicle cycles:

CLTC-P for category M1 passenger cars;
CLTC-C for N1 light commercial vehicles and eligible M2 vehicles up to the specified mass limit.

Passenger-EV range claims normally refer to CLTC-P. A comparison should state the cycle variant rather than using “CLTC” as if every light vehicle followed one trace.

How CLTC-P was constructed

The China Automotive Technology and Research Center developed the cycle from large-scale driving data intended to represent Chinese traffic. The development work grouped operation into low-, medium- and high-speed conditions and constructed a transient trace with a substantial share of low-speed and idle operation. China Automotive Technology and Research Center: Development of the China automotive test cycle

The CLTC-P trace has three phases:

low speed: 674 seconds and about 2.45 km;
medium speed: 693 seconds and about 5.91 km;
high speed: 433 seconds and about 6.12 km.

The complete cycle lasts 1,800 seconds and covers approximately 14.48 km. Maximum speed is 114 km/h. Average speed including stops is about 29 km/h, and idling occupies roughly 22% of the time.

Those characteristics explain much of the familiar direction of the result. Compared with Europe’s four-phase passenger-car WLTC, CLTC-P covers less distance in the same time, has no 131.3 km/h extra-high phase and gives greater weight to low-speed transient operation.

Step 1: select and prepare the vehicle

The test uses the applicable vehicle category, test mass and configuration. The manufacturer supplies required vehicle and battery-electric-range information, while the test agency applies the conditions and tolerances in the standard.

Driver-selectable modes follow the prescribed selection rules. Tyres, vehicle mass and the configuration represented by the result matter because they affect both resistance and battery demand. A headline range should therefore be tied to its wheel, tyre and powertrain version.

The vehicle is charged, conditioned and soaked according to the procedure before testing. Ambient and battery conditions are controlled. This creates repeatability, but it does not reproduce an arbitrary hot, cold or high-speed trip.

Step 2: reproduce road load on the dynamometer

The CLTC-P speed trace is only the driver’s target. The chassis dynamometer must separately reproduce the resistance of the represented vehicle configuration.

The applicable test mass, wheels, tyres, tyre pressure and aerodynamic state are established under the Chinese light-duty test provisions. Road resistance is determined through the permitted road-load method and represented by coefficients that can be expressed conceptually as:

F(v) = f0 + f1 × v + f2 × v²

The lower-order terms contain much of the rolling and mechanical resistance. The quadratic term is dominated by aerodynamic drag, so body shape and frontal area still matter even though CLTC-P gives more weight to low-speed operation than European WLTC.

The target road load is converted into settings for the dynamometer’s power absorber. Because the tyres and rollers already create some laboratory loss, the absorber applies the remainder required for the complete system to reproduce the target. The process is verified through the applicable coastdown and tolerance checks. Cooling airflow from a fan is not used as a substitute for the calibrated aerodynamic force. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods China National Standard GB/T 38146.1-2019: China automotive test cycle for light-duty vehicles

This distinction matters when comparing two CLTC claims. The vehicles can follow exactly the same speed trace while the dynamometer demands different wheel power because their road-load curves, test masses and configurations differ. CLTC-P’s lower average speed reduces the aerodynamic share of the combined result, but its high phase still reaches 114 km/h.

Step 3: choose the full or shortened depletion method

GB/T 18386.1 provides a conventional cycle method and a shortened method for determining energy consumption and electric range.

Under the conventional method, a fully charged EV repeatedly follows the applicable CLTC until it reaches the prescribed test-termination condition. Distance and electrical energy are recorded, and the incomplete final operation is handled under the standard’s calculation rules.

The shortened method reduces laboratory time for long-range vehicles. Its broad sequence is:

Begin with the fully charged and conditioned vehicle.
Drive two CLTC cycles in the first dynamic test segment.
Deplete the battery more quickly in a constant-speed segment, normally at no less than 100 km/h when vehicle capability permits.
Drive two further CLTC cycles in a second dynamic segment at lower state of charge.
Continue through the final constant-speed portion to the test end condition.
Recharge the vehicle and record the required energy.

The constant-speed sections accelerate depletion; they do not simply replace the energy consumption of the CLTC trace. The calculation uses the prescribed relationship between the dynamic segments, battery energy and distance.

This structure resembles the engineering problem solved by the WLTP shortened procedure, but similarity does not make the results interchangeable. Each standard has its own trace, definitions, tolerances and equations.

What does empty mean in CLTC testing?

Displayed 0% is not a universal definition of an empty battery. The GB/T procedure uses its prescribed test-termination condition and measures battery energy through that endpoint. The battery-management system still protects the cells from a damaging deep discharge. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

If the display reaches 0% while the vehicle remains capable of continuing the regulated depletion sequence, energy used after 0% can form part of the test-measured usable energy. Energy remaining below the propulsion cutoff is not available to the test, even though it is physically stored in the cells.

The usable-energy result therefore does not reveal the size of a below-zero reserve by itself. That requires the displayed state of charge, DC discharge energy and final battery-management limits to be observed together. A difference between a Chinese advertised capacity and a foreign-market capacity is not sufficient evidence that CLTC discharged the battery further.

Step 4: measure electrical energy

Battery voltage and current are recorded so DC energy can be integrated through the driving portions:

DC energy = integral of battery voltage × battery current over time

The recharge after depletion provides the electrical input needed for the standard’s energy-consumption determination. AC input and DC discharge answer different questions because the former includes charging losses.

The exact reporting field must be checked before comparing a CLTC energy-consumption value with an EPA label or an in-car display. Dividing range into the wrong energy boundary can produce a plausible but false battery-capacity estimate.

Step 5: calculate energy consumption and range

The conventional procedure builds range from the distance achieved through repeated CLTC operation to the defined termination condition, with the required treatment of the final cycle.

The shortened procedure estimates the CLTC-equivalent range by joining measured usable battery energy with the energy demand measured in the dynamic CLTC segments. In simplified physical form:

CLTC range = usable battery energy / CLTC energy consumption per kilometre

The official calculation contains the detailed weighting, correction and end-of-test treatment. The simple equation explains the energy balance but should not be used as a replacement certification formula.

Current EV listings sometimes describe CLTC as a raw test followed by a generous universal “correction factor.” That description is misleading. The test procedure contains regulated calculations, but there is no sound basis for converting every CLTC EV range to WLTP or real-world range with one fixed multiplier.

Why CLTC range is often longer

At lower speed, an EV spends less energy overcoming aerodynamic drag. Frequent deceleration creates regenerative-braking opportunities, and efficient electric drivetrains avoid much of the low-load penalty seen in combustion vehicles.

CLTC-P’s high phase is shorter and slower than a sustained Chinese expressway journey. A tall vehicle with a large frontal area may therefore look closer to a low-drag car in the combined cycle than it would at a steady 120 km/h. The ordering can change again in cold weather if the vehicles have different cabin and battery thermal systems.

This is a cycle-shape effect, not evidence that the measured distance is fictitious. It does mean the number is poorly suited to direct motorway planning.

How to compare a CLTC claim

First determine whether the number is:

a certified CLTC-P result under GB/T 18386.1-2021;
a preliminary manufacturer target;
an older NEDC-based Chinese value;
a test for a different vehicle category;
a claimed maximum from one wheel or trim configuration.

Then compare city-like and high-speed behavior with independent tests. Keep charging losses separate from in-car energy consumption. Avoid converting with a generic ratio unless it is clearly labelled as a rough observation from a defined vehicle sample.

CLTC is useful for comparing vehicles certified under the same Chinese procedure. Its limitations become serious when its combined result is presented as if it described every road, speed and climate.