In a typical household, heating, ventilation, and air conditioning (HVAC) costs are among the biggest contributors to monthly electricity bills. Residential and industrial HVAC systems require significant power to maintain a comfortable indoor environment, operating almost continuously year-round.
The same principles apply to EV HVAC system design. While an EV’s cabin is much smaller than a home, maintaining a comfortable temperature — especially in extreme climates — still demands substantial energy. Any loss of heated or cooled air forces the system to work harder, increasing energy consumption.
Unlike home HVAC systems that draw power from the electrical grid, an EV’s HVAC system relies solely on the vehicle’s traction battery. This creates a parasitic load, directly reducing driving range. To minimize this loss and maximize the coefficient of performance (COP), modern EVs utilize sophisticated heat pumps and complex heating and cooling loops that regulate the cabin, battery, electric motors, and inverters. These advanced systems depend on intelligent sensors to precisely control refrigerant and coolant flow, ensuring optimal temperature regulation and energy efficiency.
To achieve these efficiency gains, EVs incorporate a range of smart sensors that optimize HVAC performance. These sensors help manage energy consumption, improve comfort, and extend vehicle range. Here's how they contribute to EV HVAC system design.
The Stress an HVAC System Puts on an EV’s Battery
Battery thermal management is a vital component of modern EV HVAC system design. Latest-generation automotive heat pump systems provide highly efficient heating and cooling for the occupant space, which is noticeable to the driver and passengers. They also feature capabilities that allow the driver to leave the vehicle unattended on hot or cold days and return to a comfortable temperature, enhancing the experience compared to legacy ICE systems.
Additionally, these new systems quietly maintain optimal temperatures for the battery, motors, and inverters without requiring input from the operator, thanks to precise monitoring of various subsystems using smart sensors.
In the short term, operating an EV’s HVAC significantly affects the vehicle’s battery — the system decreases the available power. With the battery’s stored energy utilized for managing the cabin’s environment, an EV’s range per charge diminishes. In extreme conditions — such as using a heater in sub-zero temperatures or running the A/C in oppressive heat — the HVAC system’s power consumption can reduce range by nearly 100 miles.
Throughout an EV battery’s useful life, stress and recharging take a toll on the power bank. Like the pair of rechargeable AA batteries in your TV remote, an EV’s battery loses capacity (the amount of power it can hold) over time. The impact of the HVAC system can have a greater effect on the overall range.
EV HVAC System Design: The Sensors Needed for System Optimization
Since HVAC use in an EV is taxing to its battery, optimizing the system is critical for preserving the vehicle’s overall performance.
Fortunately, electric vehicle HVAC systems feature a more sophisticated design than those in your home. Smart electric vehicle sensor technology enables these systems to self-regulate and manage energy consumption. However, this isn’t possible, without sensor technology providing feedback to the system and its operator for it to run efficiently and use only the power necessary.
Sensors that are a must for optimizing EV HVAC system design include:
(Click each sensor to jump to its section)
Outside Air Temperature Sensor
Unless you’ve selected the air recirculation option for an electric car heating and air conditioning, the air that’s heated or cooled for the cabin’s climate comes from outside. An outside air temperature sensor provides the data for how hard the HVAC system will need to work to bring air temperatures into the desired range. For instance, heating -20℉ air will take more power to warm up than air at 20℉. The intake air temperature sensor is also critical to modeling the heat rejection from the various components and heat exchangers.
Discharge Air Temperature Sensor
Just as understanding the starting temperature of the air is important to regulating an HVAC system and its power consumption, so too is the temperature of air that’s been heated or cooled. A discharge air temperature sensor tells the system how hot or cold the air exiting the HVAC system is. With that information, the system can determine if it needs more or less energy to bring air temperatures within a comfortable range in the cabin.
Refrigerant Temperature Sensor
Refrigerant is key for cooling a vehicle’s:
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Interior climate
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Motors
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Inverters
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Battery
This happens through an expansion cycle within the evaporator core: the refrigerant extracts heat from the cabin environment and rejects it when compressed. Refrigerant temperature monitoring allows precise control of the expansion cycle to minimize power loss while absorbing the maximum heat.
Refrigerant Pressure Sensor
Hand-in-hand with maintaining the proper refrigerant temperature is keeping an appropriate refrigerant pressure. This provides critical information on the high-pressure and low-pressure sides of the electrically controlled expansion valves. It also monitors flow control valves and flow reversing functions, allowing optimum heat exchange for each system subcomponent.
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Evaporator Temperature Sensor
The evaporator core extracts heat from the passenger cabin through refrigerant expansion. The air passing through the evaporator fins can contain water vapor, which can freeze on the fins and restrict airflow. To prevent icing of the evaporator fins, the evaporator surface temperatures must be controlled to 1 - 2℃ above the freezing point. An evaporator temperature sensor provides accurate temperature measurement to direct the expansion valve which regulates the evaporator’s temperature and keeps it from dipping below the freezing point.
Air Flap Sensor
Air unable to move through an EV’s duct freely requires fans to use more energy, drawing more power from an EV battery. Air flap sensors check how air moves through the system and give positional feedback to switch between recirculating internal air or bringing air from outside.
Air Filter Monitoring Sensor
Air filters within the HVAC system provide clean air to the cabin, eliminating dust, pollen, and other allergens from the cabin air space. In dusty environments, this filter can become plugged and restrict airflow into the vehicle, forcing the system to work harder. Air filter monitoring provides prognostic data to the automobile, allowing for planned air filter replacement before it becomes a problem.
Automatic Defog Sensor
Taking the human element out of keeping the windshield free of condensation, an automatic defog sensor monitors the surface temperature, air temperature, and relative humidity to determine the condensation point of the windscreen. Through high-accuracy monitoring, the system can automatically provide the minimum heat to the defroster airflow to provide a clear windshield without overcompensation.
Sun Load Sensor
Taking HVAC optimization in a unique direction, sun load sensors measure the infrared spectra (the sunlight that provides heat) of light hitting an EV car and understand its angle and intensity. With this information, the electric vehicle heating and cooling system can adjust how it is heating or cooling a car, providing warmer or cooler air where needed most. For example, if the sun is on the car’s passenger side, the sensor tells the system to provide more cooling to that side. All this thermal modeling requires accurate and reliable sensors to provide critical inputs for the control system.
Seat and Steering Wheel Temperature Sensors
It might seem like an odd addition to this list, but it comes into play when managing an EV’s HVAC system. When a driver or passenger activates a seat heater or steering wheel warmer, the vehicle instantly registers and responds to the input. With smart technology, the vehicle’s systems can prioritize power distribution to heat the seat or steering wheel instead of heating the air. Accurate sensing provides critical comfort feedback to make the occupants comfortable in the most efficient manner.
Electric Vehicle HVAC System Design Optimization for Peak Performance
Considered a necessity for a comfortable ride, the operator interface for an electric vehicle HVAC system is designed to be intuitive with minimal requirements for the operator to monitor or modify.
Smart sensor technology integrated into an electric vehicle heating and cooling system’s design ensures the vehicle lives up to expectations and runs as intended with minimum waste energy and intelligence that allows the driver to focus on the road.
Bring New Efficiency to Your Electric Vehicle HVAC System
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(Editor's note: This article was originally published in January 2022 and was updated in March 2025.)
