Diesel Bunk Heater for Semi Trucks and Sleeper Cabs

A bunk heater is a diesel-fired air heater that warms a truck sleeper while the engine is off, burning roughly 0.04–0.13 gallons per hour (0.14–0.47 L/hr) instead of the 0.8 gallons an idling Class 8 engine burns. Over a ten-hour night that is about three quarters of a gallon against eight.

You are here because you want heat in the bunk without idling — either to comply with anti-idling rules, to stop burning fuel you are not paid for, or because the factory unit in your truck has quit. This page covers all three.

What is a bunk heater, and what does it cost to run overnight

A bunk heater is a self-contained diesel burner, about the size of a shoebox, that pulls fuel from your truck’s main tank and blows hot air into the sleeper. It runs off the truck batteries and needs no engine, no shore power and no propane bottle.

Parts catalogues sell the same box under half a dozen names. Truck bunk heater, semi truck bunk heater, diesel bunk heater, bunk diesel heater, sleeper heater, semi sleeper heater, night heater, parking heater — and a listing for a heater for truck sleeper cabs is the same product again.

And yes, a diesel bunk heater burns diesel: the same fuel already in your saddle tanks, drawn through a standpipe rather than a separate bottle or jug.

The running cost is the reason fleets buy them. Here is the arithmetic for a ten-hour night, with diesel at $3.80 a gallon:

Method	Fuel per hour	10-hour night	Cost per night
Engine idling	~0.8 gal	~8 gal	~$30
Apollo-V1 bunk heater (2.5kW)	0.036–0.067 gal	0.36–0.67 gal	$1.40–$2.55
Apollo-V2 bunk heater (5kW)	0.053–0.125 gal	0.53–1.25 gal	$2.00–$4.75

That gap is also what makes the unit legal to use where idling is not. Around thirty US states and most Canadian provinces cap discretionary idling at roughly five minutes, and auxiliary heaters are the standard exemption written into those rules.

The second saving is the engine itself. An hour of idling counts as roughly an hour on the meter and puts wet, unburnt fuel past the rings — a bunk heater adds nothing to either.

How do bunk heaters work

Bunk heaters burn a fine diesel mist inside a sealed steel chamber, then blow cab air across the outside of that chamber. The two air paths never touch. Combustion gas leaves through its own exhaust pipe under the truck.

How a bunk heater works in a semi is no different from one in a van or a boat. Same burner, same control board, bigger duct.

How does a bunk heater work, step by step

1. You press start. The blower spins up and purges the chamber.
2. The ceramic glow pin heats to over 1,100°C (2,012°F) within about 60 seconds.
3. The metering pump begins ticking, delivering measured diesel pulses to the burner.
4. The mist lights, the flame sensor confirms it, and the glow pin switches off.
5. Cabin air is drawn across the heat exchanger fins and pushed out the duct at temperature.

From cold, expect warm air in about four minutes and a usable sleeper temperature in ten to fifteen. That last figure depends far more on how well your cab is sealed than on the heater.

Why cabin air never touches exhaust

The combustion chamber is a closed vessel with its own inlet and its own outlet. Cabin air passes over the outside of it and is heated by contact, never by mixing.

Ours is drawn from 2520 stainless steel (25Cr20Ni), which holds its shape at burner temperatures rather than distorting after a few winters. A distorted chamber is how a cheap unit starts leaking combustion gas into the cab.

What the controller is actually doing

The controller does more than set a temperature. It watches flame, overheat and supply voltage, and it shuts the burner down before any of the three becomes a problem.

Low-voltage cutout matters most to you. If cranking voltage drops too far the heater stops rather than flattening the batteries you need to start the truck in the morning.

2.5kW or 5kW — sizing a bunk heater for your sleeper

For a standard 60–72 inch sleeper, 2.5kW is the right size; go to 5kW for a raised-roof, double-bunk or condo cab, or if you regularly park below -20°F (-29°C). Factory heaters fitted to most sleepers are rated around 2kW, so a 2.5kW unit already sits above the OEM benchmark.

Bunk heaters for trucks are sized by cab volume, not by truck weight. There is no single best bunk heater for semi truck use, because cab volume varies more than the heaters do.

Bunk heaters for semi trucks split cleanly on that one measurement. A diesel bunk heater for semi truck sleepers under 72 inches is a 2.5kW job; anything larger is a 5kW job.

Your cab	Model	Output	Duct
Day cab, small sleeper, single bunk	Apollo-V1	2.5kW / 8,500 BTU	Ø60mm
Standard 60–72″ sleeper, one driver	Apollo-V1	2.5kW / 8,500 BTU	Ø60mm
Raised roof, condo, double bunk, team	Apollo-V2	5kW / 16,500 BTU	Ø75mm
Regular operation below -20°F (-29°C)	Apollo-V2	5kW / 16,500 BTU	Ø75mm

One mistake to avoid: oversizing. A 5kW unit in a small sleeper reaches setpoint fast, then cycles on and off all night. Cycling is louder, burns more fuel than a steady low burn, and puts every start through the glow pin.

Sizing up only pays when the cab is genuinely bigger or the nights are genuinely colder. Otherwise the smaller heater running long and low is the quieter, cheaper, longer-lived setup.

Diesel, coolant or electric — and why 12V electric fails overnight

For overnight bunk heat, a diesel air heater is the only one of the three that works on battery power alone. The other two have narrow, specific uses.

Type	What it heats	Overnight on batteries?
Diesel air (Apollo-V1 / V2)	Cab air directly, through ducts	Yes — 1–2A running draw
Diesel coolant (Apollo-C1)	Engine coolant, then cab via the OEM heater core	Yes, but slower and it also warms the block
12V electric bunk heater	Cab air, by resistance element	No

The electric case is worth spelling out, because an electric bunk heater for semi truck use sounds like the simpler option. A 12V resistance heater producing meaningful heat pulls 60–100A. Ten hours of that is 600–1,000 Ah — several times what a truck’s battery bank holds.

The 2.5kW diesel unit produces the same heat on 1–2A because the energy comes from fuel, not from the battery. The battery only runs a pump, a blower and a control board.

A coolant heater like the Apollo-C1 diesel water heater is the right pick when you also want the engine warm for a cold morning start, or when your truck already has a hydronic loop plumbed in. For bunk heat alone, the air heater gets there faster.

Apollo-V1 and Apollo-V2 diesel bunk heater specifications

Both models are the same platform in two sizes, and both run the same controller, the same Kyocera ceramic glow pin and the same 2520 stainless combustion chamber. The difference is output and duct diameter.

Our diesel bunk heaters are also the units we build for boats and campers. A bunk heater for trucks differs only in duct diameter and standpipe length.

Specification	Apollo-V1	Apollo-V2
Heat output	2.5kW / 8,500 BTU	5kW / 16,500 BTU
Fuel consumption	0.136–0.252 L/hr (0.036–0.067 gal/hr)	0.201–0.475 L/hr (0.053–0.125 gal/hr)
Voltage	12V or 24V DC (specify at order)
Start current	~8A at 12V for 2–3 minutes, then 1–2A running
Lowest operating temperature	-40°F (-40°C)
Maximum altitude	11,483 ft (3,500 m)
Combustion chamber	2520 stainless steel (25Cr20Ni)
Glow pin	Kyocera SN362 silicon nitride, M10×1, ≥1,100°C (2,012°F) at 60 seconds
Exhaust	304 stainless flexible spiral, Ø25mm × 60cm supplied
Hot air duct	Ø60mm × 60cm	Ø75mm × 60cm
Main harness	4.5 m (14.8 ft)
Controller	EasyStart Pro LCD with barometric sensor, plus remote
Warranty	1 year standard; extendable to 2 or 3 years total

The standpipe is what makes it a bunk heater

Out of the box these are air heaters. What turns one into a bunk heater is the fuel standpipe that drops into your truck’s main tank so the unit feeds itself.

The Apollo-V1 air parking heater takes a 307mm or 600mm standpipe depending on tank depth. The pickup sits above the tank floor, so the heater cannot pull your tank below a starting reserve.

The spiral exhaust, and why the cheap ones rust through

Budget heaters ship a 201 stainless or aluminised straight pipe — about 4% nickel. Acidic condensate from combustion eats through it, usually at the low point where water sits.

Every Vvkb heater ships with 304 stainless at roughly 8% nickel. The spiral wall also attenuates combustion noise through destructive interference, so you do not need a separate silencer bolted on.

Certifications and approval numbers

The Apollo-V1 holds ECE type approval under UN Regulation 122 (heating systems), approval number E24*122R00/06*0054*00, and under UN Regulation 10 (EMC), approval number E24*10R06/02*4825*00. Both were issued by NSAI, the National Standards Authority of Ireland, in 2023, and cover 12V and 24V DC.

These approvals cover the Apollo-V1 only. The Apollo-V2 carries CE, RoHS and FCC. Tell us which model you need and we will send the exact documentation we hold for it.

Model	Approvals held
Apollo-V1 (2.5kW)	ECE R122 · ECE R10 · CE · RoHS · FCC
Apollo-V2 (5kW)	CE · RoHS · FCC
Apollo-C1 (coolant)	CE · RoHS

Approval certificates are issued to our manufacturing company in China and name it as the certificate holder. Full PDFs go out with any quotation, and the numbers above can be checked independently — the Vvkb certifications page lists where.

Installing a bunk heater in a semi truck sleeper

Most sleepers have an empty under-bunk storage compartment, and that is where the heater goes. Budget four to eight hours for a first install, or a few hundred dollars at a shop that already fits APUs.

Bunk heater installation comes down to five decisions, and four of them are about where the pipes go rather than where the box goes.

You do not strictly need a bunk. Drivers also mount these on the passenger floorboard or in the box between the seats when the under-bunk space is taken.

Wherever it lands, a bunk heater for semi truck sleepers has to vent downward and outside, and it has to pull combustion air from outside the cab. Those two rules decide the position; everything else is convenience.

What decides where it goes

• Exhaust must exit downward and outside, away from any air intake or window, with a continuous fall so condensate drains out rather than back into the burner.
• Combustion air must come from outside the cab, never from the sleeper.
• The fuel pump belongs low, close to the tank, tilted 15–35° with the outlet upward.
• Leave yourself access. You will pull the glow pin and the screen at some point. A unit buried behind a bolted panel turns a 30-minute job into a day.
• Duct the outlet at floor level, pointed along the bunk rather than straight at your head.

The full sequence with tools and torque points is in the step-by-step diesel heater installation guide. Fleet shops fitting these in volume can ask us for the wiring and mounting drawings directly.

Already running factory bunk heaters in Freightliner, Volvo, Kenworth or Peterbilt cabs

If your factory bunk heater has stopped, work through power first, then air, then fuel — in that order. Most trucks leave the line with an Espar Airtronic or a Webasto Air Top, and the failure patterns are consistent across Freightliner Cascadia, Volvo VNL, Kenworth T680, Peterbilt and International cabs.

The badge on the cover tells you less than you would think. Freightliner bunk heaters and Cascadia bunk heaters are usually the same Espar unit, while Volvo bunk heater and Kenworth bunk heater fitments split between Espar and Webasto depending on build year and spec.

That matters when you are sourcing parts. A screen, a glow pin or a fuel pump for an Espar bunk heater fits several of these trucks, and Thermo King dealers stock most of the consumable items.

What you see	Most likely cause	First check
Control panel completely dead	Fuse, not the heater	Cascadias often have a small fuse box near the batteries with a 20A and a 5A — not in the three cab boxes
Cranks, white smoke, no light-off	Carbon in the burner and screen	Pull the glow pin screen; heavy smoke at the exhaust confirms it
Runs on cold nights, quits around 40°F	Lost flame during cycling	Shut down 15 minutes, restart; if it will not hold, the burner needs service
Nothing happens after repeated attempts	Lockout	These units lock out after roughly 20 failed starts or 3 overheats — clearing it needs a diagnostic tool
Starts, then stops within minutes	Supply voltage	Under about 10.5V the heater shuts itself down by design

Two things that save you money here. Do not keep pressing start — every failed attempt counts toward the lockout, and clearing a lockout costs a shop visit that the first three attempts would not have.

And do not replace the glow pin on suspicion. It is the expensive part and it is usually not the fault; the screen and the small orifice above it are. A multimeter settles it in a minute — 0.4–0.6 Ω is a healthy 12V pin, 1.3–2.2 Ω a healthy 24V one.

Off-season, run the heater at least 15 minutes a month. Carbon buildup is a storage problem more than a running problem, and a monthly burn is what stops it. Our heater fault code and troubleshooting guide covers the error codes in detail.

Bunk heater parts: exhaust pipe, fuel pump, glow pin, control panel

Four parts account for most bunk heater failures, and all four are replaceable in the truck. Sizes are common across Vvkb, Webasto, Espar Airtronic D2/D4 and the Chinese 2KW–8KW units, so a part that fits one usually fits the others.

Part	Why it fails	Fit check before you buy
Glow pin	Ceramic cracks or the element opens after thousands of cycles	M10×1 thread, ceramic Ø4.5 × 44.7mm. 0.4–0.6 Ω = 12V, 1.3–2.2 Ω = 24V
Bunk heater exhaust pipe	201 stainless and aluminised pipe rust through at the low point	24mm inner diameter (25mm nominal). Measure your run before ordering length
Bunk heater fuel pump	Ticks but will not meter, usually after fuel contamination	Match voltage and stroke volume to your heater’s output rating
Bunk heater control panel	Display fails or buttons stop responding	Match the connector and the heater generation, not just the brand

Single parts for owner-operators ship from our retail store — the diesel heater exhaust pipe and Kyocera glow plug are the two most ordered. Shops and fleets buying by the box should use the heater parts range and ask for trade pricing.

Frequently asked questions

Does a bunk heater drain your batteries overnight?

No. The glow pin pulls about 8A for the first 2–3 minutes, then the heater settles to 1–2A for the blower, pump and control board. Across a ten-hour night that is roughly 15–20 Ah.

A Class 8 truck with four group-31 batteries holds somewhere around 600–800 Ah, so a full night of heat costs you about 3% of the bank. The controller also has a low-voltage cutout that stops the heater before your starting capacity is at risk.

How much fuel does a bunk heater use, and how long can you run one?

0.036–0.125 gallons per hour depending on model and heat setting, and you can run it continuously. There is no duty-cycle limit — plenty of drivers leave one running from October to March.

An Apollo-V1 on a medium setting burns under half a gallon across a ten-hour night. Ten hours of idling burns about eight. The fuel standpipe sits above the tank floor, so the heater cannot draw your tank down to empty.

Why won’t my bunk heater start, and what does the white smoke mean?

White smoke with no light-off means carbon has built up in the burner and around the glow pin screen. That is the single most common failure, and it is a cleaning job rather than a replacement.

Check in this order: fuses and battery voltage above 10.5V, then intake and exhaust for snow or obstruction, then the burner screen. If the unit has been cranked repeatedly with no light-off, assume it has locked itself out — that needs a diagnostic tool, and more start attempts only bury it deeper.

Do I need an actual bunk to install a bunk heater?

No. The under-bunk compartment is the usual spot because it has floor space and a straight exhaust drop, but the passenger floorboard and the box between the seats both work.

What the location has to give you is a downward exhaust exit away from any intake, outside combustion air, a short fuel run to the tank, and enough access to pull the glow pin later without dismantling the cab.

Is a cheap Chinese bunk heater a fire risk?

The risk is real and it is worth naming, because it comes from three specific things rather than from the country of manufacture. We build in China, so this is our problem to answer rather than dodge.

Cab fires in these units trace back to undersized wiring shorting under vibration, a missing or non-functioning overheat sensor, and thin exhaust pipe rusting through inside the cab structure. Our units ship with a 4.5m harness sized for the load, an overheat sensor and flame sensor wired to shut the burner down, low-voltage cutout, and 304 stainless exhaust. The Apollo-V1 also went through ECE R122 — a burner-safety type approval with a number you can check.

None of that replaces a CO and smoke alarm in the sleeper. Fit one whatever you buy.

Is a “bank heater” or “bunker heater” the same thing?

Yes — those are just common misspellings of bunk heater. You will also see it listed as a sleeper heater, night heater, cab heater or parking heater, and truck parts catalogues use all of them interchangeably.

The one term that means something different is APU. That is a small auxiliary engine, not a heater.

Bunk heater or APU — which should I buy?

A bunk heater if you want heat; an APU if you also need cooling and battery charging. The bunk heater costs a fraction of an APU, weighs a fraction, and burns roughly a tenth of the fuel.

What it does not do is run your air conditioning in July or keep an inverter fed. Many owner-operators run a bunk heater for winter and a battery-powered cooling setup for summer, and come out ahead of a single APU on both purchase price and maintenance.

How long does it take to warm a sleeper from cold?

Warm air in about four minutes, a comfortable bunk in ten to fifteen. A 2.5kW unit and a 5kW unit reach setpoint at similar times in a standard sleeper, because the small one runs steadily while the large one starts cycling.

How well the cab is sealed matters more than heater size. Curtains closed and vents shut can halve the warm-up time.

Can I fit one myself, or does it need a shop?

Most of the install is mechanical, and a competent DIYer takes four to eight hours. The two steps that catch people out are drilling the tank for the standpipe and routing the exhaust with a continuous downward fall.

If you are not comfortable opening the fuel tank, any shop that fits APUs can do the fuel side in an hour. The installation guide shows every step with photographs.

Related guides

• Diesel truck heater — truck cab heat without idling — the wider truck heating picture, including engine preheating
• How to install a diesel heater — the full step-by-step with tools and photographs
• Heater fault codes and troubleshooting — what each error code means and what to check first
• Diesel heaters — the full range, air and coolant, 2.5kW to 12kW