How Much Power Does a Diesel Air Heater Consume During a Night Cycle?

Owners often focus on fuel consumption, but a diesel air heater also draws a small but steady electrical current from the vehicle battery. Because the unit is designed to heat air rather than coolant, its fan and fuel pump run continuously while the flame is on. Estimating this draw helps travelers size their leisure batteries and avoid a flat morning start.

Electrical Load by Phase

During startup, the glow plug briefly pulls the most current, commonly around 30 to 45 watts for a short burst on a 12-volt system. Once running, the load drops sharply: the combustion fan and axial air mover together usually draw between 15 and 35 watts, with the fuel pump adding only a few watts. On a 24-volt truck system the current halves, though wattage stays similar.

Average Overnight Drain

Over an eight-hour night, a heater that cycles on and off to hold a set cabin temperature may run the flame for three to five hours in total. Adding the brief glow-plug bursts and controller standby, a realistic average electrical draw lands near 20 to 30 watts. That translates to roughly 0.2 to 0.3 amp-hour per hour on a 12-volt bank, or about 2 amp-hours overnight for a small camper.

Units with a higher heat setting run the fan faster and use more power, while thermostatically controlled low burn keeps the load near the lower end. Owners who combine the heater with a fridge and lights should size the battery so that overnight heating leaves enough charge to start the engine.

Reducing Parasitic Load

Keeping filters clean and ductwork unrestricted lets the fan run at a lower speed for the same airflow, which trims wattage. Parking the cab out of the wind and closing external curtains also means the heater reaches setpoint sooner and cycles less, reducing both fuel and electrical use over the night.

Comparing With Fixed Electric Heaters

To put the draw in context, a 1500-watt mains electric heater would drain a vehicle battery at many times this rate if run from an inverter. The diesel air heater avoids that burden because its heat energy comes from fuel, while electricity is reserved for the small fan and pump. This is why off-grid travelers can run the heater all night without the huge battery bank a purely electric setup would demand.

Owners who measure their battery state of charge in the morning often report that the heater accounts for a modest slice of overnight drain, with the fridge and lights taking a larger share. Tracking the draw over a few nights reveals how much headroom a particular battery bank really has.

References

GB/T 7714: YEK P N Y, LAU C E, LAU S Y, et al. A novel microwave air heater integrated with thermal energy storage [J]. International Journal of Energy Research, 2022, 46(13): 19269-19277.

APA 7th: Yek, P. N. Y., Lau, C. E., Lau, S. Y., et al. (2022). A novel microwave air heater integrated with thermal energy storage. International Journal of Energy Research, 46(13), 19269-19277.

MLA 9th: Yek, P. N. Y., et al. "A Novel Microwave Air Heater Integrated with Thermal Energy Storage." International Journal of Energy Research, vol. 46, no. 13, 2022, pp. 19269-19277.