Bottom Line
Gen sets and APUs
With 22 states and municipalities having idle-restriction laws, and more expected this year, what do you do? For the next few years at least, on-board electric or auxiliary power will remain the best way to provide year-round in-cab climate control and creature comforts with the main engine off.

by Paul Abelson, technical editor

As in most things trucking, when it comes to idle reduction alternatives, one size doesn’t fit all. 

Fuel-fired heaters are excellent for cold climates, but do nothing for hot conditions. Shore power is a great energy source to run all manner of on-board accessories, but it requires a place to plug in, not readily available now or in the immediate future.

Figuring your payback
APUs and gen sets cost anywhere from $3,000 for hardware alone to upward of $11,000 for a fully featured APU factory or dealer installed. That’s a lot of money, even at the low end. 

A generator to drive 110-volt accessory heaters and air conditioners can be installed by the owner, but APUs that tap into a vehicle’s air-conditioning system should be professionally installed.

With that much tied up, how can you calculate payback? It’s simply a matter of calculating annual fuel and maintenance savings less the cost of operating and maintaining the unit. Also subtract any revenue changes if the weight of your tractor is a factor. Add in the fines you’ll save if you operate in jurisdictions that enforce anti-idling regulations. That gives you the net annual savings. Then add the purchase price, taxes and installation costs to get your total acquisition cost.

Divide the total acquisition cost by your savings and you’ll get a decimal number. That will be roughly the time, in years, that it will take to get your initial outlay back. For example, if cost is 1.43 times annual savings, it will take around 1.43 years to reimburse yourself. So after 1 year, 5 months and 1 week of operation, you will have back all you paid for the unit. After that, all the savings go right to your bottom line.

Most manufacturers have interactive payback calculators on their Web pages.

The basics
The terms “generator” and “APU” are not interchangeable. Despite their many similarities, they are different. Both use fuel from the main tanks. Both have small displacement diesels, mostly made by Kubota.

Gen-set engines are connected directly to a generator that produces anywhere from 3.5 to 8.0 kilowatts; that electricity powers any and all accessory units, which are self-contained and often remotely located.

APUs use similar diesels to drive an alternator for maintaining battery level. For climate control, most use heat from their engines’ coolant to keep both the cab and the truck engine warm. Each has its own air-conditioner compressor and condenser units, belt-driven by the APU’s small engine.

It is easier to route wires and cables than coolant hoses and refrigerant lines, so accessories and systems can be located anywhere in the cab or on the truck. Less costly items like household ceramic space heaters can be used.

APUs use many existing systems, simplifying installation and eliminating the need for added components.


Pony Pack
Pony Pack’s president and founder, former trucker Rex Greer, deserves special note because of his efforts to persuade Congress and government agencies to institute incentives — such as weight allowances, tax relief and tax credits — for the installation of idle-reduction equipment. The weight allowance written into draft versions of the energy bill is largely the result of his efforts. He is the organizer of the new Idle Elimination Manufacturers Association and was instrumental in the formation of the Diesel Idling Reduction Partnership, a users’ group promoting idle reduction through education.

The Pony Pack fits within a 2-foot cube, at 21 by 22 by 22 inches. It has a 2-cylinder Kubota 482 low-noise engine. Cooling capacity is up to 30,000 Btu, depending on the truck’s evaporator. The Kubota produces between 50,000 and 60,000 Btu of hot coolant to be circulated through the main engine and the cab’s heating system. A 110-amp 12-volt alternator powers the cab fans and “hotel loads” — refrigerators, TVs, computers, microwaves and similar comfort items — with any surplus going to keep the batteries charged. An inverter will provide household (110/120 volt) current. It weighs about 300 pounds, installed.

Willis APU
This unit, from Auxiliary Power Dynamics, can be set to automatically turn on when the main engine is shut off, and to shut off when the main engine is started. It monitors voltage and temperature, and can turn on when required during prolonged truck shutdown. With a 3-cylinder Kubota 722, outputs are 54,500 Btu for air conditioning and 42,000 Btu for heating.

Willis has an air-compressor/air-starter option and an oil pump for the main engine. An engine-independent air compressor allows the use of an air starter without the need for a bulky reserve air tank. An air starter and an alternator can eliminate all but one battery. The oil pump can continue to circulate oil for cooling and to prevent oil coking. It can pre-lube the engine prior to starting. Start-up is when most engine wear takes place.

Related news
RigMaster offers quality cab comfort (heating and cooling with house current), and gives OOIDA members a $300 dealer/manufacturer’s rebate. Call Member Services at 1-800-444-5791.
Bergstrom and Espar have united technologies in the Nite system that offers heating and cooling comfort from deep cycle batteries, At 200 pounds, the system operates for 10 hours under normal conditions.

This APU has a 130-amp 12-volt alternator standard. Options include a 185-amp alternator and a Xantrex 1,500-watt inverter. The Willis also takes up about a 2-foot cube with its aluminum diamond plate housing. The basic unit weighs 332 pounds. The air compressor and oil pump bring that up to 370 pounds, but the net addition after the removal of two batteries is about 250 pounds.

Generator Sets

Aux Generators manufactures the Hawk and Genhawk. Both use a 2-cylinder Kubota engine. Both maintain 70 degrees F in 100-degree ambient temperatures using independent 15,000 Btu cooling units. The Hawk has a 90-amp 12-volt alternator. The Genhawk adds a 4,000-watt, 110-volt generator. The Hawk measures 18 by 24 by 24 inches. The Genhawk is 2 inches taller, and weighs 335 pounds installed.

Double Eagle
Before most people heard of generator sets, Double Eagle was offering a custom-built generator for its custom-built mansions-on-wheels. The Gen-Pac uses a 3-cylinder Kubota 905 to provide 5 kilowatts to as much as 8 kw of power. There’s also a 51-amp alternator for battery charging. The base unit weighs 435 pounds.

Double Eagle will paint their 36- by 26.25- by 31-inch aluminum box to match your truck, and can provide a matching toolbox for those who want symmetry. Stainless steel cladding is extra.

Energy and Engine Technology Corp.
Energy and Engine Technology Corp. launched its AXP 1000 generator set last year. The 26- by 18- by 19-inch package weighs less than 300 pounds. The DC alternator provides 50 amps. There is one 20-amp AC circuit and three 15-amp circuits. Accessories include 9,000 Btu cooling and 1,500-watt electric heater.

Frigette offers a 5.5 kw, 2-cylinder generator with a 40-amp alternator at 12 volts. Dry weight is 240 pounds. Box size is 23 by 20 by 21 inches. They also make an ultra-compact 3.5-kw, 1-cylinder generator designed to fit under a cab step. It, too, has a 40-amp alternator for battery charging. It measures 30.5 by 22.5 by 15.5 inches.

Frigette has an optional under-bunk electric HVAC unit with 1,500 watts of electric heat available (5,115 Btu) and 9,000 Btu of air conditioning. The entire system weighs about 340 pounds, depending on configuration.

Tag-A-Long, formerly Ulti-Max, makes the Idle Eliminator, a 6-kw generator with another 20 amps of DC power. This is the only unit that uses an air-cooled diesel. Its box is 32 by 23 by 24 inches, made of marine-grade aluminum, polished 304 stainless steel or powder-coat steel. Heating and cooling are accomplished by stand-alone electric units. The Max-Air offers 10,300 Btus of cooling and 6,800 Btus of heating. Tag-A-Long has a larger option, a 14,000-Btu cooling package.

Teleflex of Canada offers the Proheat4, a 4-kw, 2-cylinder unit with a 40-amp alternator. The relatively compact 28.5- by 25- by 18.5-inch unit weighs about 400 pounds complete with its accompanying Climate Control Unit. Mounted in the cab, it takes up 12 by 15 by 28 inches. It cools with 12,000 Btu, or heats with 3,000 watts. A 26.5- by 17- by 7.5-inch outside-mounted condenser is included in its 400-pound weight.

Teleflex has been instrumental in getting legislation passed that provides financial incentives in Canada for the purchase of idle-reduction technology.

Truck-Gen also has two sizes of generator available, a 2-cylinder, 5,500-watt model and two 3,500-watt units with a one-cylinder Kubotas. The larger unit is 25 inches wide by 24 inches deep by 24 inches tall. With 13,500 Btu air-conditioner capacity and 1,500-watt heater strips in the HVAC, the unit is 415 pounds in its box.

A 3,500-watt unit sits in a 30- by 16- by 22-inch box. It uses the same HVAC as the 5,500-watt unit, but weighs 335 pounds.

Another 3,500-watt configuration, the “Slimline,” is narrower at 16 by 19 by 32 inches. Its box is diamond plate. The “standard” 3,500-watt unit’s box looks like a Peterbilt toolbox.

Truck-Gen makes a “hybrid” APU/gen set at 3,500 watts. It has a 40-watt alternator, its own belt-driven A/C compressor and fully contained refrigerant (R-134a) system. Buyers have a choice of in-cab A/C modules: under the bunk, in a clothes closet or shelf-mounted. The latter could be externally mounted behind the rear bulkhead of the sleeper.

All Truck-Gen gen sets and hybrids have coolant and refrigerant systems NOT tied into the truck’s engine or air conditioner. While that requires more components, it allows engine systems to continue to operate unimpeded in the event of problems with the generator.

Generators and APUs are expensive. While they do save fuel and fines, and provide significant benefits for full-time truck dwellers, payback may be as long as three to five years; less if engine maintenance is factored in. Financing is available from most APU and generator manufacturers.

Paul Abelson can be reached at

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