Hot water power washers use specific fuels to heat water in the burner system. The most common options include diesel, kerosene, propane (LPG), natural gas, and electric heating elements. Diesel and kerosene dominate mobile units, while propane and natural gas suit stationary setups, and electric models avoid combustion fuels entirely.

This guide breaks down each fuel type with clear pros, cons, and use cases. You will learn how these washers produce heat, what drives costs, and key safety factors. Expect comparison tools, real-world examples, and tips to avoid common pitfalls. By the end, you will know how to match a fuel to your jobs, budget, and site conditions.

Separate the machine’s power source (electric motor or engine that drives the pump) from the heating fuel (what fires the burner to heat water). Many users mix these up, which leads to poor choices. This article focuses on heating fuels, but touches on power sources where they overlap.

Read more in detail: hot water vs cold water power washing.

How Hot Water Power Washers Produce Heat

Hot water power washers clean more effectively than cold ones because heat breaks down grease, oil, and grime more quickly. The machine pumps water through a heating coil. A burner or electric element raises the temperature to 60-100°C or more, depending on the model.

The pump runs on electricity, a petrol engine, or a diesel engine. That is separate from the burner fuel. For example, an electric-powered washer can have a diesel burner for heat. Or a petrol engine drives the pump, while propane heats the coil.

Burners in fuel-fired units work like a controlled flame. Fuel mixes with air, ignites, and heats the coil as water flows through. Good ventilation is essential here, as combustion produces exhaust gases.

Electric hot water units skip the burner. Heating elements warm the water directly, like a giant kettle.

Common fuel types for hot water pressure washers

Hot water pressure washers heat water by pushing it through a steel coil while a burner fires underneath. Your fuel choice affects heat output, soot and maintenance, fumes and ventilation rules, cold weather reliability, and running cost.

Two quick ideas that help everything make sense:

• Flow rate (GPM or LPM) controls how hot the water can get. Higher flow usually means lower outlet temperature unless the burner is very powerful.
  
• Cleaner-burning fuels usually mean less soot, which often means fewer coil cleanouts and more stable performance.

Diesel

Diesel is popular because it is easy to source and works well for contractor and field jobs.

How it behaves

• Produces strong heat and recovers temperature well under heavy use.
  
• Can create more soot, especially if the burner is out of tune, the nozzle is worn, or the air intake is restricted.
  

Best for

• Mobile contractors, construction, mining, agriculture, fleet washing.
  
• Greasy and heavy soil where you want strong heat and long run time.
  

Pros

• Widely available, easy refuelling.
  
• Strong heat output for degreasing.
  
• Good for long shifts without swapping cylinders.
  

Cons

• More soot risk, coil and combustion chamber may need more frequent cleaning.
  
• Stronger exhaust smell and stricter ventilation requirements.
  
• Fuel quality and storage contamination (water, algae growth) can cause burner issues.
  

Maintenance tips

• Keep a clean fuel filter and water separator if fitted.
  
• Replace burner nozzle on schedule (worn nozzles change spray pattern and create soot).
  
• If soot builds up, your coil acts like it is “wrapped in a blanket,” reducing heat transfer and raising fuel use.

Kerosene

Kerosene is often chosen when you want less soot and steadier burner performance.

How it behaves

• Typically burns cleaner than diesel, so the coil stays cleaner longer.
  
• Less likely to thicken in cold conditions compared with diesel, depending on local fuel blends.
  

Best for

• Frequent use where downtime matters.
  
• Colder climates or early-morning winter work.
  
• Indoor or semi-indoor areas (still need proper venting because combustion produces carbon monoxide).
  

Pros

• Cleaner combustion, often fewer deep coil cleanouts.
  
• More stable flame and easier ignition in some setups.
  
• Less smell than diesel for many users.
  

Cons

• Can be more expensive or harder to source in some areas.
  
• Still a flammable liquid with storage rules.
  
• Some burners are tuned for a specific fuel, so swapping between diesel and kerosene can require adjustment.
  

Maintenance tips

• Still inspect for soot, just usually less of it.
  
• Use clean storage containers and keep water out of the tank.

Heating oil

Heating oil is similar to diesel in many systems, but availability depends on your region and site setup.

How it behaves

• Comparable heat output to diesel in many burners.
  
• Soot and smell can be similar to diesel, depending on grade and burner tuning.
  

Best for

• Fixed facilities that already store heating oil.
  
• Industrial sites with controlled fuel supply.
  

Watch-outs

• Local rules can be strict about storage tanks and spill controls.
  
• Burner compatibility matters; not every unit is rated for every oil grade.

Propane

Propane is a great option when you want cleaner exhaust and less soot, and you can manage cylinders safely.

How it behaves

• Very clean burn, usually minimal soot.
  
• Heat is strong, but it depends on burner design and gas supply consistency.
  
• In cold weather, propane vaporization can drop if the cylinder is too small for the draw, causing a weaker flame.
  

Best for

• Workshops, wash bays, food-adjacent areas, and indoor-capable setups with correct venting.
  
• Sites that hate the smell or soot.
  

Pros

• Clean combustion, reduced coil fouling.
  
• Often quieter burner sound and less odour.
  
• No liquid fuel spills during refuelling.
  

Cons

• Cylinders must be stored, transported, and secured correctly.
  
• You can run out mid-job if you do not size cylinder capacity properly.
  
• Cold weather performance depends on cylinder size and draw rate.
  

Practical tips

• Use the right regulator and hose rating.
  
• If the flame “weakens” in cold conditions, larger cylinders or twin-cylinder setups help.

Natural gas

Natural gas is usually the most convenient fixed-install option if you have a piped supply.

How it behaves

• Clean, consistent flame similar to propane.
  
• Very steady supply, so temperature consistency can be excellent.
  

Best for

• Permanent wash bays running daily: fleets, factories, agriculture facilities, distribution centres.
  

Pros

• No cylinders to swap, no liquid fuel storage on-site.
  
• Clean burn with low soot.
  
• Often, predictable operating costs for high-usage sites.
  

Cons

• Not mobile.
  
• Requires installation, gas plumbing compliance, and sometimes permits.
  
• If gas pressure is inadequate, performance suffers.

Comparison Table for Hot Water Power Washers

A Fuel Types at a Glance comparison table gives readers a quick, decision-ready snapshot of the most common burner heating options for hot water pressure washers. It typically lines up diesel, kerosene, propane (LPG), natural gas, and electric heating side by side so you can compare what matters fast: heat output, cleanliness (soot and coil maintenance), running costs, portability, indoor suitability, storage needs, and key safety risks like ventilation, CO, and fire hazards.

Fuel Type	Heat Performance	Operating Cost Drivers	Maintenance Level	Emissions/Ventilation	Safety Risks	Portability
Diesel	High	Fuel price + soot cleaning	High (soot)	High (needs a strong vent)	CO, fire, spills	Good
Kerosene	Medium-High	Fuel price + less cleaning	Medium	Medium-High	CO, contamination	Good
Propane	Medium	Tank refills	Low	Medium (vent required)	Leaks, tank handling	Medium
Natural Gas	Medium	Utility rates	Low	Medium	Gas leaks	None (stationary)
Electric	Medium	Electricity rates	Low	None	Electrical faults	Depends on power

Read More In Detail: Pressure Washing Chemicals

How to Choose the Right Fuel for Hot Water Power Washers

To choose the right fuel for a hot water pressure washer burner, match the fuel to your work environment, your mobility needs, and your maintenance tolerance.

1. List your main jobs (grease removal, outdoor only, indoor possible).
2. Note site constraints (portable vs fixed, ventilation, power access).
3. Set budget limits (upfront cost vs running cost).
4. Shortlist 2-3 fuels that fit.
5. Check machine compatibility and local fuel prices.
6. Test or read reviews for real performance.

Choose this if…

• You need max heat and mobility: Go diesel.
• You want less cleaning hassle: Pick kerosene.
• You work indoors sometimes: Consider propane with venting.
• You have a fixed bay with a gas line: Select natural gas.
• You prioritize zero fumes: Choose electric.

Always confirm with the manufacturer’s manual.

Maintenance and Operating Costs

Fuel choice impacts long-term expenses.

Diesel often shoots coils faster. Clean regularly to maintain efficiency. Kerosene and propane reduce this.

Poor fuel quality clogs filters and nozzles. Use clean sources and change filters often.

Total cost of ownership includes fuel price, maintenance, and downtime. Diesel may cost less upfront, but requires more coil cleaning. Natural gas saves over time in fixed setups.

Read More In Detail: Pressure Cleaning Methods.

Maintenance and Troubleshooting Linked to Fuel

explains how the fuel you use affects burner performance, reliability, and common faults. It covers fuel-specific issues like soot buildup, clogged filters, poor combustion, and storage contamination, plus the routine checks and fixes that keep hot water pressure washers heating properly.

Fuel quality drives most burner issues.

• Sooting: Higher with diesel; clean coils annually, use soot remover additives.
  
• Burner tuning: Adjust air bands for a clean flame, no smoke.
  
• Nozzle/filter clogging: Change nozzle every 500 hours; inspect filters daily.
  
• Fuel contamination: Water causes white smoke; drain separators.
  
• Odour/smoke: Often poor tune or wrong fuel return or switch to a cleaner option.

Safety and Handling Tips for Hot Water Power Washers

Fuel-fired burners produce carbon monoxide, an invisible killer. Never run them in enclosed spaces without proper exhaust venting. Install CO detectors nearby.

Store fuels in approved containers away from heat sources. Refuel only when cool. Check for leaks regularly.

Follow local regulations for storage and use. OSHA guidelines limit CO exposure in workplaces. A review of kerosene hazards highlights respiratory risks from poor handling.

Hot surfaces on coils can burn. Wear gloves and keep a distance after use.

Maintenance and Troubleshooting by Fuel Type

Different fuel systems fail in different ways, so match your maintenance to the burner type.

• Diesel and kerosene (fuel oil burners):
  These can create soot over time, especially with poor fuel or the wrong air mix. Clean the heating coil and burner area about every 100 to 200 hours, or sooner if the water heat drops, smoke appears, or the performance feels weak. Also, check the fuel filter and nozzle.
  
• Propane and natural gas:
  These usually stay cleaner, but they still need the burner checked and tuned about once per year (gas pressure, flame quality, safety shutoffs).
  
• Electric hot water units:
  In hard water areas, scale builds up inside the coil or heater. Descale on a schedule based on your water hardness, and whenever heating performance drops.
  
• Fuel storage problems (all fuel types):
  Dirty or old fuel causes clogs and poor combustion. Keep tanks sealed, use a proper filter or water separator, and replace filters before they plug up.

Common Mistakes and Myths About Power Washers

Many people assume all power washers work the same way, but small misunderstandings can cause poor cleaning results, equipment damage, and safety risks. One common myth is that more pressure always means better cleaning. In reality, the best results come from balancing PSI (pressure), GPM (water flow), the right nozzle, and the correct cleaning chemical. Using too much pressure on soft surfaces like timber, painted walls, or vehicle panels can strip coatings and leave permanent marks.

Another mistake is skipping basic safety steps. Some users treat the spray like a normal hose, but a high-pressure jet can cut skin and force debris into eyes. Poor cable management with electric washers and missing RCD protection can also create serious electrical hazards, especially in wet areas. People also underestimate setup details like hose length, nozzle size, and water supply. Starving the pump due to low flow, clogged inlet filters, or running without proper priming can damage seals and shorten pump life.

Conclusion

The right fuel balances heat needs, costs, maintenance, and safety for your specific jobs. Diesel and kerosene power most mobile work, propane and natural gas serve fixed setups well, and electric shines for fume-free areas.

Review your workflow, site limits, and budget. Test options if possible. A smart choice saves time, cuts downtime, and keeps your cleaning effective for years.

Ready to upgrade or maintain your setup? Explore quality hot water power washers and accessories to match your fuel decision.

FAQs

What fuel do most hot water power washers use for heating?

Diesel and kerosene lead the pack for mobile units. Propane and natural gas appear in stationary models, while electric skips fuel entirely.

Is diesel or kerosene better for a hot water power washer burner?

Kerosene burns cleaner with less soot, while diesel gives hotter output. Choose kerosene for easier maintenance and diesel for maximum heat.

Can you use propane in a hot water power washer?

Yes, many models offer propane burners. They burn clean and suit areas with good tank access.

Do hot water power washers run on electricity only?

Some do. Electric-heated models use elements and produce no exhaust, perfect for indoor use.

What is the safest fuel for hot water power washers?

Electric avoids combustion risks. Among fuels, propane and natural gas burn cleaner, but all need proper venting to manage CO.

How much fuel does a hot water power washer use?

Expect 3-6 litres or kg per hour, depending on model and load. Costs vary by local prices and efficiency.

Can I switch between diesel and kerosene?

Often yes, but check your manual. Adjust burner settings if needed for best performance.

Why do some burners produce more soot?

Diesel creates more than kerosene due to higher wax content. Poor tuning or bad fuel worsens it.

Are there eco-friendly fuel options for burners?

Biodiesel blends work in compatible units. Electric heating offers the greenest site operation.

How do I reduce carbon monoxide risk?

Vent exhaust outdoors, use CO detectors, and never run in confined spaces. Follow safety standards like those from OSHA.