Best Size Diesel Heater for Your Caravan Or Motorhome

Keeping warm in your caravan or motorhome is on the top of the list for many travelers, especially those who travel during the cold season. When searching for the perfect diesel heater, there are many options out there that can heat up your motorhome. However, you will need to choose what heater works best for you based on the size of your caravan or motorhome.

The best size diesel heater for your caravan or motorhome depends solely on the size of the space you need to heat. You have two size options for diesel heaters: 2kW or 4kW. If you own a Class B or B+ motorhome, a 2kW will suffice. Anything larger (Class A or Class C) will need a 4kW heater. 

Ensuring you have the right size heater for your space will be important when you encounter cold weather. Every caravan or motorhome should have a decent diesel heater on board since cold-weather camping and traveling is a must for many. Read on to learn more about what size diesel heater will work best for you and your family during those long trips.

How Does a Diesel Heater Work?

Understanding how your diesel heater operates can make a difference in cost and repair if you encounter any issues on the road. All brands of diesel heaters will have the same components listed below. 

  • Heater unit
  • Fuel pump
  • Inlet/outlet

Accessories that come with your heater will depend on the brand and model you decide to purchase. More expensive models will likely come with more accessories, but you have to decide which of those you really need.

Heating Unit

The main component of your diesel heater will be the heating unit. The heating unit will be mounted inside of your caravan or motorhome using a mounting plate for easy access. On one end of your unit, there will be a fan that retrieves cold air and brings it into the unit to warm it up. 

After the unit brings in air, it is sent through a combustion chamber that heats the cold air and makes it warm. Fuel is entered from underneath the unit by the fuel pump and goes through the combustion process to heat the air. Once the air is warm, it exits the unit through the other side through the duct and into your motorhome to heat the space.

Your unit will continue to take air in as long as your motorhome has reached the desired temperature. Most models of diesel heaters will come with a remote that will allow you to set your desired temperature, like a thermostat.

A concern often brought up about diesel heaters is possible exposure to carbon monoxide. Diesel heaters emit very little carbon monoxide. The little carbon monoxide that is produced by these heaters is released outside of your motorhome through the exhaust outlet. You do not have to worry about carbon monoxide building up inside your motorhome.

However, for an extra layer of safety and peace of mind, purchase a carbon monoxide alarm to install within your motorhome. 

Fuel Pump

Before your diesel fuel enters the unit, it goes through the fuel pump. The fuel pump regulates the amount of fuel that enters the unit without overwhelming it or causing it to overheat. Depending on your unit and the fuel needed, you can increase or decrease the fuel dosage using the fuel pump.

When installing your diesel heater, you want to make sure that your fuel pump is mounted vertically. This will avoid any bubbles from building up in your pump and allow for optimal performance. 

Before your first use of a diesel pump, you will need to prime the fuel line. Priming the fuel line will lubricate it with diesel fuel. If you do not prime the fuel line first, you will not get the lubrication needed in order for your heater to run properly. 


Your diesel heater will have tubes running from it called inlet and outlet tubes. There is an air inlet and air outlet tube. These tubes bring cold air into the unit and take the hot air out of the unit into your space. Furthermore, there is an exhaust outlet that will filter the fumes outside of your motorhome, preventing carbon monoxide from building up inside your motorhome.

These are the main components of your diesel heater that will allow it to run. For the full installation instructions of your heater, follow the provided instruction manual of the unit that you purchase. 

Can You Get Different Size Diesel Heaters?

When purchasing a diesel heater, you will want to buy one that is optimal compared to the size of your caravan or motorhome. The best size diesel heater for your caravan or motorhome depends solely on the space you need heated. If you buy a diesel heater that is too small for your motorhome or caravan, it will not properly warm the space and waste energy.

When searching for a diesel heater, you have two main size options for diesel heaters.

  • 2kW
  • 4kW

If you own a Class B or B+ motorhome, a 2kW heater will suffice. If you have a larger motorhome, such as a Class A or Class C, you will need a 4kW heater. Using a 2kW to heat a Class A or C motorhome will increase fuel usage and power costs. Below is a chart that shows the best size heater compared to the size of your motorhome.

Size of MotorhomeClassHeater
29 to 45 FeetClass A4kW
17 to 19 FeetClass B2kW
17 to 30 FeetClass B+2kW
30 to 33 FeetClass C4kW

There are a few other size options for a diesel heater beyond 2kW or 4kW, but those sizes will be your best two options to choose from depending on the size of your home on wheels. If you own a small, mostly canvas motorhome, you will need to consider purchasing a 2.2 kW heater due to more heat loss due to the canvas. 

Does a Larger Size Make Enough of a Difference Compared to the Smaller Size?

The simple answer to this question is yes. The size of your heater makes a significant difference in how much space it can heat efficiently and effectively. A smaller-sized heater will take much longer to heat a class A or C-sized motorhome.

  • If you are using a heater that is too big, you will not be able to leave it on high. This will cause your heater to be in an idle position for extended periods of time and cause an abundance of carbon build-up. A heater that is too big for your motorhome will routinely shut on and off causing more noise and disruption.
  • Conversely, having a heater too small for your motorhome will require the heater to be on high for the majority of the time. Having the heater on high for extended periods of time will be noisier and more of an inconvenience. 

Also, if you try to heat one of the larger motorhomes using a smaller heater, you will see an increase in fuel usage, and, over time, costs will be much higher. On the other hand, if you purchase a large diesel heater for a small motorhome, you are likely wasting money on equipment you do not fully need.

How Much Does a Diesel Heater Cost?

When deciding to install a diesel heater in your caravan or motorhome, you will need to evaluate the costs and determine what works best for your situation. Some costs associated with a diesel heater include:

  • Initial Purchase
  • Installation
  • Repairs
  • Fuel Costs

While these costs can add up, buying the proper diesel heater for your caravan or motorhome will save you wasted money in the long run.

Initial Purchase

After determining the size of the heater you need to adequately heat your space, you will next need to purchase your heater. A 2kW diesel heater will range from $100 to $150 depending on the make and model you decide to purchase. On the other hand, a 4kW heater will cost in the range of $150 to $200.

Along with purchasing the unit itself, you will need an installation kit, which is where the real money lies. For an installation kit, you will be spending anywhere from $800 to $1,100. It is important to get an installation kit that works with your motorhome to allow your heater to be in a safe and sustainable position. 


Once you purchase your diesel heater, you now have to decide whether to install it yourself or pay to have it installed in your motorhome. While installing it yourself may be more cost-efficient, you run the risk of incorrectly installing it if you do not have the required expertise. Here is a guide to follow if you choose to install on your own.

Hiring an expert to install your heater will ensure that it gets installed correctly and is safe. The cost of an installation can be in the range of $700 to $1,500. In the long run, it may be worth forking out the cash to avoid possibly needing to repair a damaged heater due to bad installation.

  • When installing your heater, you should look for a space within your motorhome that allows the heater to be hidden and in a safe location.
  • Although you want to easily access your heater, you do not want to keep it out in the open where it could possibly get bumped.
  • This will also reduce noise pollution within your motorhome. 

Most traditional caravans or motorhomes do not have a diesel fuel tank, and one will need to be installed for your heater. Installing a diesel fuel tank will depend on the space you have within your motorhome. If you own a motorhome that already runs on diesel, then your heater can be installed to retrieve fuel from the main tank. 


Just like any other component of your motorhome, you will have to plan for malfunction and repairs on your heater. It is possible for your fuel pump to misfire, causing your unit to not properly heat the air entering your motorhome. 

The typical lifespan of a diesel heater is 10 years, and then it will need to be replaced. In some cases, a company will offer a two-year warranty on heaters. In the case that your heater needs to be repaired, you will have to determine whether it will be cost-effective to repair or replace it.

When repairing or replacing your diesel heater, you will need to remove it from your caravan. Be sure to remove the heater properly to ensure that wires do not get damaged or that gas does not leak. 

If you do not feel comfortable or do not have experience in repairing a diesel heater, find a service shop that can repair your heater. On the other hand, if you are repairing on your own, then you will need to make sure you have sufficient workspace to take apart your heater. 

Fuel Costs

Generally, a diesel heater will cost less than running a heater on electricity. A diesel heater will use about 0.1 liters of fuel per kW. When using your heater for the first few times, track how much fuel it takes to completely heat your motorhome. This will provide you with insight into how much fuel you are actually using with your diesel heater.

The average cost of diesel fuel in 2020 was $2.50. When deciding to run a diesel heater in your caravan, be sure that you are considering the price of diesel fuel and fitting it into your travel budget. You do not want to be caught without money for fuel and risking having a caravan without proper heating. 

Once you become comfortable with using your diesel heater and track how much fuel you are buying, you can begin to adjust your trailer to keep those fuel costs to a minimum. Here are some environmental tweaks you can consider to keep your heat trapped inside your caravan.

  • Thermal Curtains
  • Thick Rugs
  • Keep Heat Outlet Clear
  • Check Your RV Seals

Thermal Curtains

Installing thermal curtains inside your caravan can go a long way when attempting to keep your hot air trapped. In cold weather, your windows will be the main culprit of letting your hot air escape. You can find inexpensive thermal curtains at your local department store.

To keep your warm air in with thermal curtains, close them at night when the sun goes down and keep them open during the day. By keeping your curtains closed at night, you will be able to trap the warm air inside your caravan and keep you and your family warm for a good night’s rest.

Thick Rugs

Just like thermal curtains, putting down thick rugs will assist with keeping your trailer warm and trapping heat. If you are planning on using your trailer for an extended time period during the winter, consider installing carpet to keep your feet off of the cold floor and your caravan properly insulated. 

Keep Heat Outlet Clear

When installing your diesel heater outlet, be sure that you are able to keep the space in front of it clear. Blocking your outlet will decrease the amount of heat being dispersed around the caravan, and you might be stuck wondering why your caravan is still cold while your heater is working at max speed. 

Check Your RV Seals

If your heater is constantly running without any noticeable temperature difference in your trailer, you may want to check the seals around your trailer. Heat will escape quickly if your trailer is not properly sealed, and this will end up costing way more than needed to keep your caravan warm.

Common places to check if you are running into this issue are under the sink, slide outs and wheel wells. Over time, insulation under your sink and wheel well may start to weather, causing hot air to escape. Furthermore, if you have a slideout on your caravan or motorhome, you should frequently check to make sure the seals are secure and tight. 

Are Diesel Heaters inside a Motorhome Noisy?

Although diesel heaters can offer a cheaper alternative to other heating options, the cons of diesel heaters come with noise. When booting up a diesel heater, the inlet and outlet valves will make a noticeable noise.

The noise comes from the exhaust, and once the motorhome is heated to the desired temperature, the noise will dissipate. If the heater is being noisy when it is not pumping fuel, it may be a sign of a needed repair.

Noise pollution coming from your heater will be most noticeable when it is running on high.

  • To reduce the noise you hear inside your motorhome, install your heater in the bathroom, under the kitchen sink, or under another storage location.
  • Avoid installing it under your bed, as you might find the noise inconvenient at night when trying to sleep.

If your heater is noisier than normal, it may be an issue with the fuel pump. You can adjust your fuel pump to reduce the noise, or it may need to be replaced completely. Also, as mentioned earlier, make sure you have the correct size heater compared to your fuel pump.

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