Installing an APU (auxiliary power unit) on a semi-truck typically costs between $8,000 and $13,000 total when you factor in both the unit and professional installation. The exact price depends on whether you choose a diesel or electric APU, buy new or used, and where the work is done. For most owner-operators, the investment pays for itself within one to two years through fuel savings alone.
New APU Costs by Type
Diesel APUs are the most common choice for long-haul truckers who need both heating and cooling in the sleeper cab. A new diesel unit from a major brand runs between $7,000 and $12,000 before installation. These units have a small diesel engine that powers climate control, charges batteries, and runs electronics without idling the truck’s main engine. Popular models from Thermo King, Carrier, and RigMaster fall in this range, with the Thermo King TriPac series sitting toward the higher end.
Electric (battery-powered) APUs cost less upfront, generally between $2,000 and $5,000 for the unit itself. These systems rely on battery banks to power air conditioning, and they recharge while the truck is driving. The trade-off is that electric APUs handle cooling well but struggle with heating in cold climates, and battery life limits how many hours of climate control you get per stop. Some drivers pair an electric APU with a diesel-fired heater to cover both seasons, which adds $500 to $1,500 to the total cost.
Installation Labor Costs
Professional installation of a diesel APU typically runs $1,500 to $3,000 on top of the unit price. The job involves mounting the APU (usually on the frame rail behind the cab), running fuel lines from the truck’s existing tank, connecting coolant lines for heating, wiring the electrical system, and integrating climate controls into the sleeper. Most shops complete the work in one to two days.
Electric APU installation is simpler and cheaper, often $500 to $1,000. There are no fuel lines or coolant connections to run. The work mainly involves securing the battery system, mounting the condenser and evaporator, and wiring everything together. Some electric units are designed as DIY installs, though getting it done at a shop ensures the warranty stays intact.
Used and Rebuilt Units
Buying used or rebuilt cuts the price significantly. A used Thermo King TriPac Evolution with standard installation runs around $6,500, though these are typically sold as-is with no warranty. That’s roughly half what a new TriPac costs installed. The risk is obvious: if the compressor or generator fails within a few months, you’re paying for repairs out of pocket.
Rebuilt APUs split the difference between new and used. A professionally rebuilt unit with new internal components (generator, starter, compressor, seals, and bearings) costs around $9,950 including parts and labor at the rebuilder’s shop. That price, roughly $10,650 after taxes at one Houston-based service center, gets you a unit that’s mechanically close to new without the full new-unit price tag. Rebuilt APUs often come with a limited warranty, making them a more reliable bet than a used take-off unit.
How Quickly an APU Pays for Itself
The payback math starts with how much fuel your main engine burns at idle. A truck engine running at idle operates at less than 10% efficiency, burning roughly 0.8 to 1.0 gallons of diesel per hour. A diesel APU, by contrast, uses about 0.15 to 0.25 gallons per hour to provide the same climate control and electrical power. That difference of roughly 0.7 gallons per hour adds up fast.
If you idle eight hours per night and drive 300 nights per year, you’re looking at about 2,400 hours of idle time annually. At 0.7 gallons saved per hour and diesel at $3.50 per gallon, that’s roughly $5,880 in fuel savings per year. An $11,000 installed APU pays for itself in under two years. Drivers who spend more nights on the road or operate in states with anti-idling laws (where fines range from $100 to $25,000 depending on the state and number of violations) see even faster returns.
Beyond fuel, idling puts significant wear on your main engine. Those 2,400 hours of idle time are equivalent to roughly 60,000 to 80,000 miles of driving wear on engine components. Reducing that wear extends the life of your engine and pushes back expensive overhauls.
Weight and Practical Trade-Offs
A diesel APU adds 400 to 600 pounds to your truck. An electric system is lighter, typically 150 to 300 pounds depending on battery capacity. For weight-sensitive loads, that difference matters. Federal regulations allow a 400-pound weight exemption for trucks equipped with APUs, meaning you can run 400 pounds over the standard 80,000-pound gross vehicle weight limit. This doesn’t fully offset a heavy diesel APU, but it helps.
Maintenance is the other ongoing cost to plan for. Diesel APUs need oil changes, filter replacements, and belt inspections, typically costing $300 to $600 per year. Electric APUs have fewer moving parts and lower maintenance needs, but battery replacement every three to five years can run $1,000 to $2,500 depending on the system.
Where to Get It Done
Truck dealerships, dedicated APU installation centers, and some truck stops with service bays all handle APU installs. Dealerships tend to charge on the higher end for labor but may offer financing packages that bundle the unit and installation into monthly payments. Dedicated APU shops, like APU Center or Truck Thermo King dealers, often have more experience with the specific wiring and mounting configurations for different cab models and can finish the job faster.
If you’re buying a used truck that already has an APU, have the system inspected before finalizing the purchase. A non-functional APU can cost $2,000 to $4,000 to repair depending on what’s failed, and that should factor into your negotiation.