How CLTC EV Range Is Calculated

CLTC-P is the passenger-car version of the China light-duty vehicle test cycle used in China’s EV range testing. Its low-speed driving profile helps explain why a CLTC figure can differ substantially from motorway range.

The cycle and the wider test procedure

GB/T 38146.1-2019 defines the driving cycle: the speed the vehicle must follow second by second, known as the speed trace. GB/T 18386.1-2021 defines the EV test conditions, battery-depletion methods, energy measurements and calculations. China’s product-admission implementation notice introduced separate reporting fields for CLTC energy consumption and range. China National Standard GB/T 38146.1-2019: China automotive test cycle for light-duty vehicles China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods China MIIT Equipment Industry Development Center: Implementation notice for EV national standards

CLTC-P applies to M1 passenger cars. CLTC-C is the separate cycle for N1 light commercial vehicles and M2 vehicles with a maximum design total mass of no more than 3,500 kg. This article focuses on passenger-car CLTC-P results.

CLTC-P has three phases:

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

Together they last 1,800 seconds, cover approximately 14.48 km and reach 114 km/h. Average speed including stops is approximately 29 km/h, and the vehicle is stationary for roughly 22% of the cycle. These figures describe one cycle; establishing an EV’s range also requires depleting the battery under the test procedure. China National Standard GB/T 38146.1-2019: China automotive test cycle for light-duty vehicles

Compared with the European four-phase passenger-car WLTC, CLTC-P covers less distance in the same time and places greater emphasis on low-speed operation. How WLTP range and consumption are measured describes that cycle and its battery test.

Prepare the vehicle and reproduce road resistance

The test vehicle represents a defined configuration. Its mass, wheels and tyres affect the resistance it must overcome and the energy required to follow the speed trace. The procedure also governs the selected driving mode and battery preparation.

For the normal-temperature test, the laboratory set point is 23°C, with a permitted deviation of ±5°C. The soak area has a 23°C set point with a ±3°C deviation. The battery is prepared and fully charged under the prescribed procedure before the driving test. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

Road load on the dynamometer

The speed trace tells the driver how fast to drive. Road load describes the resistance the vehicle must overcome at that speed.

GB/T 18386.1-2021 refers to Annex CC of GB 18352.6-2016 for road-load measurement and dynamometer settings, with specified adaptations for this test. If the manufacturer supplies the resistance curve, supporting information must be confirmed by the test agency. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

A road-load curve can be expressed as:

F(v) = f0 + f1 × v + f2 × v²

Here, F is the resistance force in newtons and v is speed in km/h. The three coefficients are fitted to the vehicle’s combined resistance across a range of speeds. The lower-order terms contain much of the rolling and mechanical resistance, while the quadratic term is dominated by aerodynamic drag.

On a chassis dynamometer, the vehicle remains stationary while its wheels turn rollers. The tyres and test equipment already create some resistance, so the dynamometer applies the additional load needed to reproduce the road target. Depending on the method used, the laboratory checks the setting by measuring how quickly the rollers slow during a coastdown or by measuring torque at the wheels. A fan supplies cooling airflow, while the rollers reproduce the calibrated road resistance. GB 18352.6-2016, Annex CC: Road-load measurement and dynamometer settings

Two cars can therefore follow the same CLTC-P trace while requiring different wheel power. Their test masses and resistance curves still matter.

Separate cold- and hot-temperature tests

Under this standard, manufacturers may use the separate cold- and hot-weather tests in Appendices A and B when they need range and consumption figures for those conditions. Amendment No. 1, effective from 1 August 2025, revises these procedures, including cabin climate-control settings and shortened testing. Those results describe different conditions from the normal-temperature test explained here. SAMR: Amendment No. 1 to GB/T 18386.1-2021 China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

Deplete the battery

The normal-temperature procedure uses the conventional cycle method for vehicles whose range does not exceed eight applicable cycles, and the shortened method for longer-range vehicles. Eight CLTC-P cycles cover approximately 116 km. Arbitration testing uses the conventional method. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

In the conventional method, the fully charged vehicle repeatedly follows the applicable cycle until it reaches the stopping condition. Battery energy and distance are recorded throughout the test.

The shortened method reduces laboratory time by inserting faster constant-speed driving between and after the measured cycle segments:

1. Start with the fully charged, prepared vehicle.
2. Drive the first dynamic segment, containing two complete CLTC-P cycles.
3. Drive the middle constant-speed segment to deplete the battery more quickly.
4. Drive the second dynamic segment, again containing two complete CLTC-P cycles.
5. Drive the final constant-speed segment until the stopping condition is reached.
6. Recharge the vehicle and measure the supplied energy.

For M1 passenger cars, the recommended constant speed is 100 km/h. Both constant-speed segments use the same speed. A higher speed can be used on the manufacturer’s recommendation with confirmation from the test agency. If the vehicle’s 30-minute maximum speed is below the recommended speed, that lower speed is used. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

The four dynamic cycles establish CLTC-P consumption at different battery charge levels. The constant-speed segments contribute to the measured battery depletion, while their distance is not simply added to the reported CLTC range.

When does the test stop?

In the shortened method, the test ends when the vehicle fails to meet the lower speed tolerance for four consecutive seconds in the final constant-speed segment. The conventional method also uses speed-trace criteria, with provisions for vehicles whose declared maximum speed is below the cycle maximum. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

The measurement runs from full charge to the test’s stopping point. If the display reaches 0% while the car can still follow the trace, the test continues to count the energy it delivers. If the car falls below the required speed, it may still have enough energy to drive at a lower speed.

EVKX defines net capacity as all the energy available to the driver from displayed 100% until propulsion stops, including any accessible reserve below displayed zero. Battery buffer and usable capacity explains the distinction between this reserve and inaccessible protective margins.

Measure battery energy and recharge energy

The laboratory records battery voltage (V) and current (I) during the test. Appendix E assigns a negative current to discharge and a positive current to energy flowing back into the battery during regenerative braking.

Net energy delivered at the battery terminals = −∫ V × I dt

The minus sign makes energy flowing out of the battery count towards the total. Energy recovered during braking reduces that total. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

After the test, recharging begins within two hours using the prescribed charging method. For AC charging, the meter sits between the supply equipment and the vehicle plug, so it counts energy lost in the onboard charger. The test may use DC if the vehicle accepts only DC charging or if the manufacturer recommends DC and the test agency agrees. In that case the meter sits between the grid and the external charger, so it counts that charger’s conversion losses. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

The recharge meter counts all electricity drawn at that point, including charging losses. Using that reading as battery energy would therefore overstate the energy available for driving. Charging Loss explains how the meter’s position changes what is included.

Calculate consumption and range

Both the conventional and shortened methods calculate range from measured battery energy and weighted battery-side cycle consumption. The conventional calculation uses the repeated cycles; the shortened calculation uses the four cycles in its two dynamic segments. Each has prescribed weighting rules, and the conventional calculation accounts for energy delivered during an incomplete final cycle. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

For consumption in kWh/100 km, the underlying relationship is:

Range (km) = test-defined battery energy (kWh) ÷ weighted battery-side consumption (kWh/100 km) × 100

For an illustrative 75 kWh of measured battery energy and weighted consumption of 12.5 kWh/100 km:

75 ÷ 12.5 × 100 = 600 km

Both inputs come from the battery side of the test. The consumption figure the manufacturer declares for certification uses the electricity drawn during recharging.

Recharge-based consumption (kWh/100 km) = external recharge energy (kWh) ÷ range (km) × 100

Multiplying the unrounded test range by recharge-based consumption in kWh/100 km and dividing by 100 gives the electricity used to recharge the car.

The certified figures can differ from the laboratory measurements. The standard accepts the manufacturer’s declaration when measured range is at least 98% of declared range and measured consumption is at most 102% of declared consumption. For repeat tests, those limits apply to the average. Published range is also rounded to the nearest kilometre, so calculating back from published figures may give a different recharge energy. China National Standard GB/T 18386.1-2021: EV energy consumption and range test methods

Use a CLTC figure to compare vehicles

Lower speeds reduce aerodynamic energy demand per kilometre. Regenerative braking recovers part of the energy during deceleration, although recovery is incomplete. A cycle with substantial slow driving can therefore produce a different comparison between vehicles from sustained motorway driving.

CLTC-P briefly reaches 114 km/h, but its high-speed phase also includes lower speeds. Its combined result does not describe a continuous journey at that speed. Normal-temperature testing also differs from driving with a cold battery and sustained cabin-heating demand.

When comparing a claim, establish:

• whether it is a certified result or a preliminary manufacturer target;
• whether it uses CLTC-P, another cycle or an older NEDC-based procedure;
• the battery, powertrain, wheel and tyre configuration;
• whether a consumption figure is battery-side or includes recharging.

There is no fixed percentage conversion between CLTC, WLTP, EPA and range on a particular journey. How EPA EV range and efficiency are calculated explains how the US system adjusts its city and highway results. For a trip estimate, use consumption measured near your intended speed and conditions, together with the battery energy available within your planned charge window. Understanding EV Range shows that calculation.