Regan Brown
Auxiliary power units (APUs) are on-board generators that power heating and air conditioning systems. They are used in trucks and aircraft. The fuel consumption of an APU depends on the type of vehicle it is used in, the power generated, and the cooling load. In trucks, APUs can consume between 0.1 and 0.5 gallons per hour when idling. In aircraft, APUs can burn 200-250 lbs per hour under full load, which is equivalent to 31-39 gallons per hour.
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What You'll Learn
APU fuel burn rate: 200-250 lbs per hour
The fuel burn rate of an APU, or Auxiliary Power Unit, varies depending on the type of APU and the power and cooling load. Traditional diesel-fuelled APUs and electric-powered APUs differ in their fuel consumption.
For example, the fuel burn rate of a diesel-powered APU can range from 0.1 to 0.5 gallons per hour, depending on usage conditions. On the other hand, electric APUs may have lower fuel consumption but require battery swaps during their lifecycle.
In the context of aircraft, the fuel burn rate of an APU can be higher, ranging from 200 to 250 lbs per hour under a full load, which equates to 31-39 gallons per hour. This burn rate can significantly impact the operational costs of an airline, especially when considering the cost of jet fuel.
It is worth noting that the fuel burn rate of an APU is not just about the start cycle but also the duration of usage. Airlines should consider the trade-off between passenger comfort and fuel costs when deciding whether to operate the APU.
Additionally, the type of aircraft and APU can influence fuel consumption. For instance, a B737 APU may consume around 80 kg of fuel per hour, while a B767 APU may consume roughly 200 kg per hour.
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Fuel burn cost: $32.55-$93.60 per hour
The fuel burn cost for an APU per hour falls between $32.55 and $93.60. This is based on the assumption that most APUs burn 200-250 lbs per hour under full load, which amounts to 31-39 gallons per hour. This figure is supported by multiple sources, which claim that the fuel burn rate for an APU is around 0.1-0.32 gallons per hour, with some claiming a higher rate of 0.5 gallons per hour, and others an even higher rate of 1 gallon per hour.
The cost per hour depends on the price of jet fuel, which has ranged from $1.05 to $2.40 per gallon over the last five years. At the lowest price of $1.05 per gallon, 31 gallons would cost $32.55, while 39 gallons would cost $41.85. At the highest price of $2.40 per gallon, 31 gallons would cost $74.40, while 39 gallons would cost $93.60.
It is worth noting that these calculations are based on the average fuel burn rate and fuel prices, and the actual cost may vary depending on various factors such as power and cooling load, outside temperature, and the specific type of APU. Additionally, there may be other costs associated with operating an APU, such as maintenance and staffing, which can impact the overall cost.
While the exact fuel burn rate and cost may vary, it is clear that operating an APU can incur significant expenses. However, it is also important to consider the benefits of using an APU, such as improved efficiency, reduced fuel consumption, and enhanced comfort for pilots and passengers. Ultimately, the decision to use an APU involves a trade-off between fuel burn cost and the potential advantages it can provide.
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Fuel burn compared to jet engines: APUs burn less fuel
The fuel consumption of an APU depends on various factors, including the power generated, cooling load, and ambient temperature. While it is challenging to make a direct comparison between APUs and jet engines due to the many variables at play, it is generally accepted that APUs burn less fuel than jet engines.
APUs, or Auxiliary Power Units, are used in various applications, including aviation and trucking. In aviation, APUs provide electrical power and cabin pressurization on the ground and during flight. In trucking, APUs are used to operate heating and air conditioning systems while the truck is idling, reducing fuel consumption and complying with anti-idling laws.
In terms of fuel burn, most APUs burn between 200 and 250 lbs per hour under a full load, which translates to approximately 31 to 39 gallons per hour. This range can vary depending on the specific APU and its usage conditions. For example, a B737 APU may consume around 80 kg of fuel per hour, while a B767 APU may burn around 200 kg per hour.
On the other hand, jet engines are designed primarily to produce thrust and generate forward motion. While they also produce electricity, it is not their primary function. As such, it is not surprising that an engine designed specifically for electricity generation may be more fuel-efficient in that regard.
Furthermore, the fuel consumption of jet engines can vary significantly depending on the size and type of the engine, as well as the operating conditions. Therefore, a direct comparison between APUs and jet engines in terms of fuel burn is complex and dependent on numerous factors.
However, it is worth noting that the fuel burn of an APU can still contribute significantly to overall fuel costs, especially when considering the cumulative effect over multiple aircraft or trucks. Therefore, while APUs may burn less fuel than jet engines, optimizing their usage and considering alternative power sources, such as ground power units, can still be essential for fuel efficiency and cost savings.
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Fuel burn and start cycles: start time doesn't affect fuel burn
The fuel burn of an APU is a topic of interest to many, especially pilots and truck drivers. It is important to note that the fuel consumption of an APU varies depending on certain factors. For instance, the fuel burn of an APU in a truck differs from that of an aircraft, and the power and cooling load also influence the amount of fuel burned.
In the case of trucks, the fuel consumption of an APU can vary between 0.1 and 0.5 gallons per hour, with some claiming it to be as low as 0.15 gallons per hour, and others estimating it to be closer to 1 gallon per hour. On the other hand, APUs in aircraft burn significantly more fuel, with estimates ranging from 200 to 250 lbs per hour under full load, which equates to approximately 31 to 39 gallons per hour.
Now, let's delve into the topic of start cycles and their impact on fuel burn. Interestingly, the start time of an APU does not significantly affect its fuel burn. Whether you start it 10, 20, or 30 minutes early, the overall fuel consumption remains relatively consistent. This is because the fuel burn is primarily dependent on the duration of the APU's operation rather than the specific time it is started.
However, it is worth noting that the start cycle itself can impact fuel efficiency. For example, in cars equipped with automatic start-stop or idle-stop systems, the engine automatically shuts off when the car is idling and restarts when the brake is released or the accelerator is engaged. This technology can lead to fuel savings, especially in city traffic with frequent idling. According to the Society of Automotive Engineers (SAE), the fuel economy improvements in testing ranged from 7.27% to 26.4%.
In summary, while the specific start time of an APU may not significantly affect its fuel burn, the overall duration of operation and the presence of efficient start-stop systems can influence fuel consumption.
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Fuel burn and anti-idling laws: APUs reduce fuel costs
The amount of fuel burned by an APU varies depending on the type of vehicle, the power generated, and the cooling load.
In the aviation context, most APUs burn 200-250 lbs per hour under full load, which equates to 31-39 gallons per hour. However, the fuel consumption of an APU can depend on the type of aircraft and the number of engines being started. For example, a B737 APU can use around 80kg of fuel per hour, while an A340 APU may require up to 500 kg of fuel per hour.
In the trucking industry, the fuel consumption of an APU can range from 0.1 to 0.5 gallons per hour, depending on the power and cooling load. This is significantly lower than the fuel consumption of an idling engine, which can use up to 1 gallon of fuel per hour.
The use of APUs can help fleets reduce fuel costs while still generating power for necessary amenities and tools. Anti-idling laws have become more prevalent, and APUs provide an alternative power source for heating and air conditioning systems, reducing the need for idling engines.
There are two main types of APUs: traditional diesel-fueled and electric-powered. Diesel-powered APUs can handle a variety of loads, including heating and cooling needs, while electric APUs are quieter and do not require additional fuel or maintenance. However, both types of APUs add weight and require space on the vehicle. Overall, the use of APUs can help reduce fuel burn and associated costs, especially when compared to the fuel consumption of idling engines or running multiple engines simultaneously.
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Frequently asked questions
The fuel consumption of an APU depends on the power generated and the load. On average, an APU burns 200-250 lbs per hour under full load, which is equivalent to 31-39 gallons per hour.
The fuel consumption of a truck APU at idle ranges from 0.1 to 0.5 gallons per hour.
The fuel consumption of an aircraft APU depends on the type of aircraft and the APU type. For example, a B737 APU uses 80kg of fuel per hour, while an A340 APU uses 500-800kg of fuel per hour.
In addition to the power generated and the load, the ambient temperature and the use of air conditioning can affect APU fuel consumption.
