How to Choose an RV Diesel Heater: BTU, Wattage & Size Guide
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Why Diesel Heating is the Smart Choice for RVs and Off-Grid Setups
If you're spending nights in your camper, caravan, or 4WD during Australian winters, a diesel heater is one of the best investments you can make. Unlike gas heaters, diesel heaters draw fuel from your existing tank, produce no open flame inside the cabin, and run efficiently on low power — making them ideal for off-grid use.
But with different kilowatt ratings and installation options available, how do you choose the right one? This guide walks you through everything you need to know.
Understanding Heater Output: kW vs BTU
Diesel heaters are rated in kilowatts (kW). The higher the kW, the more heat output. Here's a quick reference:
- 2kW heaters — ideal for smaller spaces like a camper trailer, rooftop tent setup, or a compact caravan up to about 10–12 feet. They're quieter, draw less power, and are easier to install.
- 5kW heaters — suited to larger caravans, motorhomes, or any space over 12 feet. They heat up faster and can maintain warmth in colder conditions (think alpine camping or winter in the Snowy Mountains).
As a rule of thumb, allow roughly 1kW of heating capacity per 10 square metres of space, accounting for insulation quality.
Power Consumption: What Your Battery Needs to Know
One of the biggest advantages of diesel heaters is their low electrical draw. Once running, most heaters consume just 10–30W — far less than an electric heater. However, the startup phase can briefly spike to 8–10A, so your battery system needs to handle that initial load.
For overnight use, a 100Ah lithium battery is typically sufficient to run a 2kW heater all night. For a 5kW unit or colder conditions where the heater cycles more frequently, a 150–200Ah setup is recommended.
Our Diesel Heater Range
We stock the AU Focus Gen 4 diesel heater kits, which come with everything you need for a complete installation:
- AU Focus Diesel Heater Kit – 2kW MZ Gen 4 — perfect for smaller caravans and camper trailers. Quiet, efficient, and easy to install.
- AU Focus Diesel Heater Kit – 5kW MZ Gen 4 — the go-to choice for larger motorhomes and caravans, or anyone camping in seriously cold conditions.
Both kits include the heater unit, fuel pump, exhaust pipe, intake pipe, fuel tank, wiring harness, and controller — everything you need out of the box.
Fuel Tank Considerations
Your heater will need a dedicated fuel supply. You can tap into your vehicle's diesel tank or use a separate auxiliary tank. We recommend a dedicated tank for cleaner installation and easier maintenance. The Finch 10 Litre Lockable Diesel Fuel Tank is a popular choice — compact, lockable, and purpose-built for auxiliary heater setups.
Mounting Your Heater
Proper mounting is critical for safety and performance. The heater should be mounted on a flat, stable surface away from flammable materials, with the exhaust routed outside the vehicle. The AUFOCUS Heavy Duty Mounting Plate is compatible with both the 2kW and 5kW units and makes for a clean, secure installation.
2kW vs 5kW: Which Should You Choose?
| 2kW | 5kW | |
|---|---|---|
| Space size | Up to ~12ft caravan | 12ft+ caravan / motorhome |
| Running power draw | ~10–15W | ~20–30W |
| Startup draw | ~8A briefly | ~10A briefly |
| Best for | Mild–moderate winters | Cold/alpine conditions |
| Noise level | Lower | Slightly higher |
Final Tips Before You Buy
- Check your vehicle's diesel tank compatibility if you plan to tap into it directly.
- Ensure your battery bank can handle the startup current spike.
- Plan your exhaust routing before purchasing — the exit point matters for safety and aesthetics.
- If you're unsure between 2kW and 5kW, go with the 5kW. It's easier to run a larger heater at lower output than to push a smaller one to its limits in cold weather.
Have questions about which heater suits your setup? Browse our full outdoor and RV range or get in touch — we're happy to help you find the right fit.