Electric Resistance Heater and PTC Heater

Electric resistance heaters create heat by passing current through a resistive element. A positive-temperature-coefficient (PTC) heater is a resistance heater whose element is designed so that its resistance rises strongly as its temperature increases.

Main forms

• Fixed-resistance heater: the element is designed to keep a comparatively stable resistance across its normal operating range. Heating power is managed mainly by switching, voltage control, pulse-width modulation, airflow or coolant flow, and external temperature control.
• PTC heater: the element's resistance increases sharply as it approaches its designed operating region. That reduces current and heat output, giving the element a self-regulating characteristic.

Both forms can heat cabin air directly or transfer heat into a coolant circuit. Both convert electrical energy into heat rather than moving heat from another source.

What self-regulating means

The PTC effect describes the behavior of the heating element, not a guarantee that the complete heater assembly or HVAC system is inherently safe. Voltage, element geometry, airflow or coolant flow, electrical insulation, connectors, sensors, control electronics, over-current protection, and fault handling still determine system performance and safety. A PTC element also has a design-specific temperature and power curve; “PTC” alone is not an efficiency rating.

What it means in an EV

Resistance heating can deliver heat without a usable ambient or waste-heat source, but it draws that energy directly from the traction battery. A heat pump can reduce electrical demand in suitable conditions by moving heat, while many EVs retain resistance heating for rapid warm-up, supplementary heat, or operation outside the heat pump's effective range. See Climate Systems in Electric Vehicles for the full system context and Heat Pump for the contrasting heating method.