Truck Component
Espar Airtronic D2 (diesel-fired bunk heater)
Espar (Eberspächer) · Apu · Diesel-fired bunk heater (no A/C)
Class 8 (sleeper cab
In production
Apu
Manufacturer
Espar (Eberspächer)
Category
Apu
Subtype
Diesel-fired bunk heater (no A/C)
Class
Class 8 (sleeper cab
What this component does
Espar Airtronic D2 is a diesel-fired air bunk heater — NOT a full APU. Provides cab heating only (no A/C, no electrical power). Heats the sleeper berth using a small diesel-fired burner that draws from the truck's main fuel tank. Used as a complement to a full APU (for redundancy) or as a budget alternative for owner-operators who don't run A/C-heavy southern routes. Espar is a German company; their bunk heaters are dominant in trucks where year-round full APU isn't needed.
Specifications
- Manufacturer
- Espar (Eberspächer)
- Category
- Apu
- Subtype
- Diesel-fired bunk heater (no A/C)
- Truck class
- Class 8 (sleeper cab
- Production
- 2000–present
- Applications
- Cold-weather cab heating only — no cooling, no electrical
Design and engineering
Small diesel-fired heat exchanger. Draws fuel from main tank (~0.05-0.10 gallons per hour). 12V electrical for fan + glow plug. Mounted under the sleeper bunk. Programmable thermostat.
Generations
- Airtronic D2 Original (2000–2015)Launch.
- Airtronic D2 with Easy Start (2016–present)Improved cold-start reliability, refined burner.
Reliability and longevity
Strong reliability in cold-climate operation. Burner needs annual service to avoid carbon buildup.
Common problems
Carbon fouling at the burner if not serviced annually. Glow plug failure. Fuel feed line clogging.
Maintenance schedule
Annual burner cleaning ($150-250 service). Glow plug replacement every 3-5 years.
Pros and cons
Pros
- ✓Much cheaper than full APU ($1,500-2,500 installed)
- ✓Lower weight than full APU
- ✓Reliable cold-weather operation
- ✓No emissions complexity
Cons
- !Heat only — no A/C, no electrical
- !Annual burner service required
- !Doesn't replace need for full APU on hot routes
Trucks that use this component
Other Apu components
- Carrier ComfortPro APUCarrier Transicold
- Idle Free Electrified APU (battery-powered)Idle Free Systems
- EV-eAUT Battery Electric APU (next-gen)Multiple (Espar, Carrier, Volvo Group)
- RigMaster Power APURigMaster (Hennessy Industries)
- Thermo King TriPac Evolution (diesel APU)Thermo King (Trane Technologies)
Related
Frequently Asked Questions
What is an APU?
APU (Auxiliary Power Unit) is a small auxiliary engine or battery system mounted on a Class 8 sleeper-cab tractor that provides cab heating, air conditioning, and 110V electrical power without running the truck's main engine. Espar Airtronic D2 is a diesel-fired air bunk heater — NOT a full APU. Provides cab heating only (no A/C, no electrical power). Heats the sleeper berth using a small diesel-fired burner that draws from the truck's main fuel tank. Used as a complement to a full APU (for redundancy) or as a budget alternative for owner-operators who don't run A/C-h
How much does an APU save in fuel?
A diesel main engine consumes 1.5-2.5 gallons per hour at idle. A diesel APU consumes 0.2-0.4 gallons per hour — saving 1.5-2 gal/hour. At \$3.50/gallon diesel and 1,500-2,000 hours of annual idle time, an APU saves $5,250-\$14,000 per year per truck. Payback period: 8-24 months depending on usage. Electric APUs save additional fuel because they consume zero diesel during operation (battery is charged while driving).
Is an APU required by law?
No — APUs are not federally required. However: most US states have anti-idling regulations limiting how long a truck can idle its main engine while parked (typical limit 5-30 minutes depending on state). California, Texas, New York have the strictest rules. APUs provide the cab climate control that anti-idling rules would otherwise eliminate. Many fleets and owner-operators consider APUs essentially mandatory for over-the-road sleeper-cab operations.
How much does an APU cost?
New diesel APU (Thermo King TriPac, Carrier ComfortPro): \$9,000-\$13,000 installed. New battery-electric APU (Idle Free, EV-eAUT factory-fit): \$8,000-\$15,000 — slightly cheaper now that battery costs have come down. Diesel-fired bunk heater (Espar Airtronic D2 — heat only, no A/C): \$1,500-\$2,500. Used APUs (5-year-old): 40-55% of original price. Theft is a recurring fleet problem — APUs are easy to steal from parked trucks and have a strong used market.
How long does an APU last?
Diesel APU service life: 12,000-15,000 operating hours before major overhaul. Battery-electric APU: 5-8 years before battery degradation requires replacement ($3,000-$6,000). At 1,500-2,000 hours per year, diesel APUs last 6-10 years before major service; electric APUs last 5-8 years before battery replacement. Both require regular PM.
Diesel APU vs electric APU?
Diesel APU (TriPac, ComfortPro, RigMaster): Unlimited duration, works in any climate, mature technology. Drawbacks: EPA Tier 4 emissions complexity, \$0.20-0.40/hour diesel cost, ~400 lb weight, theft target. Electric APU (Idle Free Lithium, OEM factory-fit): Zero emissions, zero fuel cost, quieter, lower maintenance. Drawbacks: 8-10 hour duration, cold-weather range limits, battery replacement expensive at end-of-life, requires depot 110V/3-phase for full recharge. California ACT mandates and emissions trends favor electric for long-term fleet planning.