Truck Topics

The Tool Box - Generators/APU's

Generators/APU's - why would you want to spend $5000 plus for one of these?

Here is my take on this subject. The average truck burns between 1 and 1.5 gallons per hour (gph) at idle, more if the engine is throttled up as some drivers do. The average generator/auxiliary power unit (APU) will burn less than .5 gallons per hour. It doesn't take a rocket scientist to figure out it will cost you less to run a generator than it will to idle your truck. With that said you must figure out, for your operation, if you can afford to purchase an APU to keep you comfortable or not.

For this discussion we will use 1 gallon per hour for the truck and .3 for the gen/APU. The figure .3 gph is what our RigMaster has consistently used for the past four years since we installed a separate fuel tank to fuel the RM only.

With fuel at 3.05 per gallon, here in NM today, idling the truck for 10 hours during your break for AC just cost you $30.50 and this does not count wear on the truck engine. The standard rule of thumb, 1 hour of idle = 100 miles of driving type wear on the engine, and could lower oil life by as much as 75%.

The APU will burn $9.15 in fuel; this engine is designed to do just this type of work. You just saved at least $21.35.

Ok, now we know how much we can save each day if we idle just 10 hours. Let's say we only need to idle or run APU 5 days a week and we work 46 weeks a year. The idle fuel will cost us $7015 for the truck or running the APU $2104.50 for a cost difference of $4910. It would stand to reason that this purchase would be a no-brainer. However, the purchase of the APU would also create other expenses in the maintenance area, the interest paid on the purchase note and it will add weight to the truck. The weight issue may rule out this purchase for some weight sensitive trucks, although the federal government has created an exemption of 400 lbs for any 1 axle if you get scaled and are overweight, Re; public law #109-58 SEC 756.

Now we can figure out maintenance for the truck and the APU. Using the calculation of 1hr = 100 miles, this is like driving 1000 miles while you sleep. This type of idling is going to increase the service intervals for your trucks engine exponentially. You should service on engine hours rather than truck miles. This will more than double your service costs, using $225.00 per service interval, assuming 125,000 miles per year and a 15,000 mile schedule, this is about 8 services per year or $1800, to about 23 services at $225.00 or $5175.00, costing you $3375.00 more per year if you service your engine properly.

Most APU's require service at about 250 hours, assuming 10 hours 5 days a week 46 weeks annually, that's 2300 hours or about 9 services per year. Our APU uses 2 quarts of oil, $15.00 per gal for $7.50, oil filter $4.27, air filter $15.42, and a fuel filter at $9.08 labor at SpeedCo $15.00 last time they did it for me for a total of $51.27, or $461.43 a year. If you were to take the APU services from the additional engine services you are still $2941 ahead by having an APU. This will more than pay the interest on the note. Adding the fuel savings to the service savings and the APU should pay for itself the first year, $4910 + 2941= $7824, enough to get an APU installed and be comfortable while saving money every year after the first.

While I do understand these numbers may be the extreme they are to make a point, the APU could save you a considerable amount of money rather than idling your truck's engine year after year.

As I said earlier, only you can decide whether or not you can justify an APU, but these numbers will help you with the calculations. I feel the anti-idle laws in this country will keep getting tougher and the only way to get required rest is with an APU running with heat or a/c as needed or get a motel for the night. I don't see the justification of a motel because we have everything in the truck we need and we could get that call with a great run at any time. I am not endorsing any one generator/APU as there are many on the market. Some are totally electric but are limited to how much capacity the batteries have as to how long they will run at one sitting. There are also systems that use shore power (you can plug them in to 110vac) that some truck stops are installing. As more trucks demand this service it will become more common.. This may be the way to go as there is no engine to maintain, but you are limited on places to park.

Just food for thought, till next time stay comfortable.