Dual Fuel vs Single Fuel Generator: Key Differences

The short version of the difference

A single fuel generator has an engine built around one fuel. Most are gasoline, though some run only on propane. You fill the tank, start it and run it until the tank is empty.

A dual fuel generator has the same kind of engine with a fuel selector. You can run it on gasoline from its built-in tank, or connect a propane cylinder with a hose and regulator and switch over. Some people also call a single fuel model a plain gas generator, which is the same idea in the search results you may have seen.

Tri fuel models go one step further and add natural gas as a third option. We cover that below.

Fuel flexibility and storage

The biggest practical difference is what you can do when fuel runs short. During a storm or long outage, gas stations may be closed or have long lines. With a dual fuel unit, a spare propane cylinder can keep you running.

Propane also stores well. Gasoline breaks down over time and can gum up a carburetor if it sits in the tank. Propane in a sealed cylinder does not have that problem, so a dual fuel generator that you start only a few times a year can be easier to keep ready.

A single fuel gasoline generator has none of that backup. If you have no fresh gasoline, you have no power. That is fine for someone who keeps fuel on hand and uses the generator often, such as on a job site.

Power output: gasoline vs propane

Dual fuel generators make less power on propane than on gasoline. The published numbers show it clearly. The Westinghouse iGen12000DFc lists 9,000 running watts on gasoline and 8,100 on propane. The Westinghouse WGen9500DFc lists 9,500 running watts on gasoline and 8,500 on propane. The smaller Westinghouse iGen5000DFc lists 3,900 on gasoline and 3,500 on propane.

This matters when you add up your loads. If your essentials add up close to the gasoline rating, you may be short on propane. Size your generator by the propane running watts if you plan to rely on that fuel. Our best dual fuel generator page lists running watts for each model so you can check both numbers.

Side-by-side comparison

Here is how the three types compare in general terms.

Dual fuel vs tri fuel

A tri fuel generator adds natural gas. That can be handy for home backup, because a natural gas line can supply fuel as long as the line is working. It is less useful for camping or tailgating, since you will not have a gas line there.

Tri fuel units also tend to be more complex, with more connections to set up. For most people who want portable power, dual fuel covers the main need: a backup for gasoline. Choose tri fuel only if you have a natural gas line at your home and plan to hook up to it.

What else to compare besides fuel

Fuel type is only one piece. Once you decide between single and dual fuel, check these specs. They matter just as much for how the generator works day to day.

Runtime is rated at 25% load, so it shows a best case. The iGen12000DFc and WGen11500DFc list 19 hours, while the WGen9500DFc lists 12 hours.

Noise and weight matter for camping and shared spaces. The iGen5000DFc lists 52 dBA and 105.8 lb. The iGen12000DFc lists 64 dBA and 189 lb.

Clean power matters for electronics. THD shows how clean the power is, and lower is better. The iGen12000DFc lists a THD of 3% or less, while the WGen9500DFc lists 23% or less.

• Running watts: use these for steady loads, not peak watts.
• Outlets: look for 240V if you plan a transfer switch or interlock kit, and TT-30R for an RV.
• CO sensor: a built-in shutoff adds a layer of safety.
• Start type: remote or electric start is easier than recoil for larger units.
• Weight: bigger tanks and engines mean heavier units.

Safety notes for both types

Every generator makes carbon monoxide, which you cannot see or smell. Run it outdoors only, well away from doors, windows and vents. Never run one in a garage, even with the door open. A unit with a CO sensor adds protection, but it does not replace a working CO alarm inside your home.

Propane and gasoline are both flammable. Store gasoline in approved containers away from heat. Keep propane cylinders upright, outdoors and out of the sun. Let the engine cool before refueling, and check hose connections for leaks before you start.

For home backup, use a properly installed transfer switch or interlock kit. Never plug a generator into a wall outlet, because that can send power back onto the grid and hurt utility workers. Have a licensed electrician do the install. Wear hearing protection if you will be near a loud unit for long periods.

Which one should you choose?

Pick dual fuel if you want a backup fuel, if you store the generator for long periods, or if you want a quieter and cleaner-burning option with propane. Pick single fuel if you use it often, keep fresh gasoline on hand and want the simplest setup.

If you are still comparing across all types of generators, our best generator page puts different kinds side by side. If you have already decided on dual fuel, start with the best dual fuel generator comparison to narrow it down by watts, runtime and noise.

Frequently asked questions

Can I switch fuels while the generator is running?

It depends on the model, so check the manual. Many people stop the generator, change the selector and then restart. Never connect or disconnect a propane hose while the engine is running.

Do dual fuel generators need more maintenance?

The engine care is much the same, with oil changes and air filter checks. You also need to inspect the propane hose and regulator for wear or leaks.

Is propane cleaner than gasoline?

Propane generally burns cleaner and leaves less residue in the engine. It still produces carbon monoxide, so the same outdoor placement rules apply.

Can I convert a single fuel generator to dual fuel?

Conversion kits exist for some models, but they can affect your warranty and safety. Check with the maker first, and have a qualified technician do the work.