Diesel Truck Heater: Cab Heat Without Idling the Engine
A diesel truck heater burns 0.026–0.124 gal/hr (0.10–0.47 L/hr) and heats the cab with the engine switched off. A Class 8 truck idling for heat burns about 0.8 gal/hr. That is the whole argument — you get the same warm cab for roughly one-sixth to one-thirtieth of the fuel, and you stay inside the 3-to-5-minute idle limits that CARB and most northern states now enforce.
Key takeaways
- Fuel: a 5KW cab heater on high uses about 0.124 gal/hr — an idling tractor uses 0.8 gal/hr
- Sizing: 2.5KW for day cabs, crew-cab pickups and small box trucks; 5KW for sleepers, insulated boxes and equipment cabs
- Power draw: around 8 A for the 2–3 minute glow-plug preheat, then 1–2 A while running
- Install: 4–8 hours for a first-timer, and everything for a standard install is in the box
- Certification: the Apollo-V1 holds E-mark type approval; the diesel air heater line is CE, RoHS and FCC certified
- Manufacturer: built by Vvkb in China since 1996 — factory direct, no trading company in between
What Idling All Night Actually Costs You
At 0.8 gal/hr and roughly 1,800 idle hours a year, a long-haul truck burns about 1,400 gallons of diesel just sitting still. That figure comes from the U.S. Department of Energy, and most fleet telematics data lands in the same range.
Run the same 1,800 hours through a 5KW diesel cab heater at mid output and you are looking at roughly 140 gallons. The difference is not a rounding error — it is a truck payment.
| One 10-hour night | Diesel burned | Fuel cost at $3.75/gal |
|---|---|---|
| Idling the main engine | ~8.0 gal | ~$30.00 |
| Apollo-V2 (5KW) on high | ~1.24 gal | ~$4.65 |
| Apollo-V2 (5KW) cycling on medium | ~0.79 gal | ~$2.96 |
| Apollo-V1 (2.5KW) on low | ~0.26 gal | ~$0.98 |
Fuel is only half of it. Idling puts about twice the wear on internal engine components as running at road speed, and the American Trucking Associations puts the added maintenance cost near $2,000 per truck per year.
The compliance side nobody budgets for
California limits diesel truck idling to 5 minutes statewide, with fines that start at $300 and reach $1,000 per violation. New York enforces 5 minutes statewide and 3 minutes in New York City, with penalties from $350 to $2,000. Illinois runs 10 minutes statewide and 3 minutes inside Chicago.
Nearly every one of those rules carves out an exemption for trucks fitted with idle-reduction equipment. A fuel-fired cab heater is the cheapest way into that exemption — it costs a fraction of a full APU, adds almost no weight, and needs no separate engine to maintain.
Worth knowing: California grants no cold-weather exemption for trucks that already have a working no-idle system. If the equipment is on the truck, you are expected to use it instead of idling.
How a Diesel Cab Heater Works (30-Second Version)
A diesel truck heater is a sealed furnace that draws a trickle of fuel from your existing tank and blows heated cabin air across a heat exchanger — combustion air and cabin air never touch.
Outside air feeds the burner through one pipe. Exhaust leaves through another, under the truck. Your cab air circulates over the outside of the heat exchanger and comes back warm and dry. Nothing from the combustion side enters the space you are sleeping in.
That separation is why a fuel-fired heater is safe to run overnight while a portable propane or catalytic heater is not. Propane dumps water vapour and combustion products straight into the cab — you wake up to wet windows and a headache.
Startup draws about 8 A at 12V while the ceramic glow plug heats for two to three minutes. Once the flame is established, draw falls to 1–2 A. A healthy pair of truck batteries will run the heater all night and still crank in the morning.
2.5KW or 5KW? Size It by Cab Volume, Not by Price
Match heater output to the air volume you are heating: roughly 2.5KW up to 200 cubic feet, 5KW from 200 to 450 cubic feet. Buying bigger than you need is the more common mistake — an oversized heater reaches setpoint too fast, shuts down, cools off, and restarts all night. Cycling is exactly the duty pattern that carbons up a burner.
| Your truck | Approx. cab volume | Model | Output |
|---|---|---|---|
| Crew-cab pickup, work truck | 90–150 cu ft | Apollo-V1 | 2.5KW / 8,500 BTU |
| Day cab tractor | 120–180 cu ft | Apollo-V1 | 2.5KW / 8,500 BTU |
| Sleeper cab, well insulated | 200–300 cu ft | Apollo-V2 | 5KW / 16,500 BTU |
| Sleeper cab, sustained −20°F (−29°C) | 200–350 cu ft | Apollo-V2 | 5KW / 16,500 BTU |
| Box truck, crane cab, service body | 300–450 cu ft | Apollo-V2 | 5KW / 16,500 BTU |
Two adjustments to that table. Add one size if your cab is uninsulated sheet metal or you park in sustained cold below −20°F (−29°C). Stay with 2.5KW if you mostly park in mild-to-moderate cold, because a smaller heater running steadily beats a big one hunting.
Both models run the same EasyStart Pro controller with a built-in barometric sensor, so fuel metering corrects itself up to 11,483 ft (3,500 m) — the reason our units keep burning clean over Donner and Eisenhower while altitude-blind heaters throw flame-out codes.
What Separates a Truck-Grade Heater From a $140 Clone
Three parts decide whether a diesel heater survives five winters or two: the heat exchanger casting, the combustion chamber alloy, and the glow plug. Everything else is a housing and a fan.
Heat exchanger: weight is wall thickness
The heat exchanger is die-cast aluminium, not folded sheet. Our 5KW exchanger weighs 2.1 kg. Budget exchangers we have weighed come in at 1.2–1.5 kg for the same rated output.
That missing weight is wall. Diesel contains sulphur, combustion turns some of it into sulphuric acid, and the acid condenses on the exchanger wall and eats aluminium. A thicker wall simply takes longer to eat through — and until it is through, exhaust stays on the exhaust side.
Casting pressure matters just as much. We cast on a 1,000-ton press, well above the 400-to-500-ton machines common in commodity die casting. Higher clamping force allows higher injection pressure, and higher injection pressure is what drives porosity out of the casting. Porosity is where acid corrosion starts.
Combustion chamber: 2520 stainless, not mild steel
The flame tube is 2520 stainless steel — roughly 25% chromium, 20% nickel, the alloy grade used for furnace internals. It holds its shape through thousands of heat cycles instead of scaling and distorting.
Glow plug and the maintenance nobody warns you about
Every fuel-fired heater on the market needs the burner cleaned and the glow plug replaced eventually. We use a Kyocera ceramic glow plug rated to light reliably at −40°F (−40°C), and the honest instruction is this: run the heater 15 to 30 minutes once a month, summer included. That single habit keeps the plug clean and the fuel line wet, and it prevents most of the "no flame detected" calls we get in November.
One symptom to know: heavy smoke from the exhaust on startup means carbon has built up inside the burner. That is a cleaning job, not a failed heater. Left alone, it becomes a failed heater.
Rated output that matches the label
A recurring complaint about no-name heaters is that a 2KW, 5KW and 8KW listing are the same unit with different stickers. Our 2.5KW and 5KW units are physically different hardware — different heat exchanger, different air outlet (Ø60mm on the V1, Ø75mm on the V2), different fuel curve. The Apollo-V1 holds ECE R122 and ECE R10 type approval under number E24*122R00/06*0054*00 — the numbers are on our certifications page and verifiable through UNECE. The diesel air heater line is CE, RoHS and FCC certified.
Installation: What It Takes and What Ships in the Box
A first-time cab installation runs 4 to 8 hours; a shop that has done a few will do it in half a day. Everything needed for a standard install ships in the box — heater, LCD controller, remote, fuel pump and bracket, exhaust muffler, intake muffler, ducting, fuel filter, standpipe, clamps and hardware. You supply the fuel tap.
Five details decide whether the install gives trouble later:
- Fuel pump distance: mount it 2–3 ft (60–100 cm) from the heater. Closer and fuel pressure runs high, burning unevenly and coking the burner. Further and output falls off.
- Fuel pickup: use the standpipe through the tank cap and leave 3/4 inch (2 cm) of clearance above the tank floor, so settled debris never reaches the pump.
- Intake clearance: leave at least 8 inches (20 cm) of open space in front of the air intake. Boxed in against a bulkhead, the heater starves and starts sooting.
- Exhaust angle: slope the whole run slightly downward. Level runs let wind blow back into the burner; upward runs trap condensate that freezes and blocks the pipe.
- Controller height: mount it at mid-cabin height. Near the roof it reads rising hot air and shuts down early — that is the real cause of most "it short-cycles all night" complaints.
Full step-by-step with tools and torque points is in our diesel heater installation guide.
Frequently Asked Questions
Will a diesel cab heater drain my truck batteries overnight?
No, not on a healthy battery bank. Startup pulls about 8 A at 12V for the 2–3 minutes the glow plug is heating, then running draw settles at 1–2 A. A 10-hour night costs you roughly 10–20 Ah. A pair of Group 31 truck batteries holds well over 200 Ah, so you are using under 10% of capacity.
If your heater is killing batteries, the batteries are the problem, not the heater. Weak batteries also cause a second symptom: the glow plug never reaches light-off temperature and you get a no-start fault on cold nights.
Why does my old heater short-cycle on mild nights and refuse to restart?
Usually the controller placement, not the heater. A controller mounted high in the cab reads the hot air that collects at the ceiling, decides the cab is at setpoint, and shuts down while the bunk is still cold. Then it restarts, overshoots, and shuts down again.
Mount the controller at mid-cabin height, out of the direct discharge stream. The other cause is an oversized heater: a 5KW unit in a small day cab reaches setpoint faster than the cab can lose heat, so it never settles into a steady burn. Repeated light-offs are what carbon up a burner.
My heater works at 20°F but quits below 0°F. What is failing?
Fuel, almost always — not the heater. Diesel starts gelling around 15°F to 10°F (−9°C to −12°C). Wax closes the heater's inline filter and the small-bore pickup line first, because they carry the least flow and sit in the coldest air under the truck.
Three fixes, in order of effort: run an anti-gel additive or winter blend; move the pickup line out of direct airflow; fit a fuel filter heater. Our units are rated to start at −40°F (−40°C) — but no heater on earth can burn fuel that has turned to wax before it reaches the pump.
How much fuel does a diesel truck heater use compared with idling?
Roughly one-sixth to one-thirtieth as much. A 5KW heater on full output uses about 0.124 gal/hr (0.47 L/hr). A 2.5KW heater on low uses about 0.026 gal/hr (0.10 L/hr). An idling Class 8 tractor burns about 0.8 gal/hr.
Over a 10-hour night that is 8 gallons idling versus 0.26–1.24 gallons on the heater. Most drivers report burning well under a gallon for a full night, because the heater cycles rather than running flat out.
Does a diesel heater need maintenance, or is it fit-and-forget?
It needs maintenance, and any supplier who says otherwise is selling you a surprise. Two habits cover almost everything: run the heater 15–30 minutes once a month year-round, and inspect the burner and glow plug annually before winter.
The monthly run keeps the glow plug from corroding and stops fuel from sitting stagnant in the line. Skipping it through a summer is the single most common reason a heater that worked fine in March will not light in November.
Is a 5KW heater really 5KW?
Ours is; a lot of them are not. The known trick in the budget market is one hardware platform sold as 2KW, 5KW and 8KW with different box art. You can spot it because the heat exchanger and the air outlet diameter are identical across the "different" ratings.
The Apollo-V1 (2.5KW / 8,500 BTU) and Apollo-V2 (5KW / 16,500 BTU) use different heat exchangers, different outlet ducting (Ø60mm versus Ø75mm) and different fuel curves. If a listing claims 8KW from a 12V unit the size of a shoebox, treat the number as marketing.
The fuel pump ticking keeps me awake. Can that be fixed?
Yes — it is a mounting problem, not a defect. The metering pump clicks once per fuel dose, and the rate rises with heat output. What makes it intolerable is bolting the pump hard to a frame rail or the bunk floor, which turns the whole panel into a soundboard.
Mount the pump on the supplied rubber-isolated bracket, hang it from a structural member outside the sleeper if you can, and keep the outlet angled slightly upward. Isolated correctly, the tick is barely audible from the bunk.
Will it work at altitude?
Yes, up to 11,483 ft (3,500 m). The EasyStart Pro controller carries a barometric sensor and leans the fuel dose as air density falls. Heaters without altitude compensation run rich as you climb, which shows up as sooting, then flame-out codes on the passes.
Above 11,483 ft, expect reduced output. If your routes regularly cross higher passes, tell us at the quote stage and we will spec accordingly.
Ready to Stop Idling for Heat?
Vvkb has built vehicle heaters in China since 1996 and ships factory direct — no trading company margin, and the engineers who answer your technical question are the ones who designed the part.
- One truck, one heater? → Apollo-V1 and Apollo-V2 on rvheater.com
- Fleet rollout, 10 units or more? → Request fleet pricing — volume tiers, lead times and install support
- Private label or OEM programme? → same form, tell us the annual volume and target market
Related pages
- Truck heaters — the full range across cab, engine and fuel heating
- Bunk heater — standpipe conversion for sleeper berths and overnight bunk heat
- Semi truck heater — Class 8 sleeper applications and APU alternatives
- Truck camper heater — slide-in campers and flatbed builds
- Truck block heater — electric coolant preheaters for cold starts
- How to install a diesel heater — step-by-step with tools and clearances