Whether you are looking for a power backup generator or power your outdoor events is a worthy investment. However, not all the best dual fuel inverter generators in the market will offer you the best experience.
Try to get any of the best dual fuel inverter generators. Remember you need to cook, probably warm your house during a storm that led to a power outage, light your outdoor party, among other things; in this case, you need a reliable generator.
A dual fuel inverter generator is what you need. A dual fuel inverter generator can run on two types of fuel; gasoline and propane. This feature qualifies it to be a hybrid generator.
There is a wide range of dual-fuel inverter generators in the market, and considering how technical this product is, settling for the best one is not easy. There are different features and specifications for each of the models available.
Here is an in-depth review of the ten best dual fuel inverter generators to help you make the best selection.
Best dual fuel inverter generators.
Champion 3400-Watt-Cold start technology
This is a top-performing, multipurpose and flexible generator for RV’s, homes and can also be used to power your construction project. Champion 3400-watt dual generator is among the popular models by the American manufacturer that utilizes the latest technology.
The generator comes in small dimensions of 25.1 × 17.3 × 18.3 inches, which is okay for a regular converter. However, this model has more power output, almost similar to largely designed generators, and it can either run on propane or gasoline. You can choose the source of fuel to use depending on its availability.
This unit has an adjustable fuel selector dial that allows quick switching of fuels. It has a 4-stroke 192cc engine size that can generate 3,400 starting watts and maintain 3,100 watts for powering your project when running on gasoline.
The generator can hold 1.6 gallons at 25% load on a full tank, and it can run non-stop for 7.5 hours. The tank is small, but it has a decent running time of 7.5 hours.
When powering it with a 20-pound propane tank, it can generate 3060 starting watts and run at 2790 watts; at 25% load, you can run this generator for 14.5 hours.
The running time on propane fuel is adequate to keep your home powered throughout the night in case of a power outage.
The unit generates clean power with less than 3% THD, which is suitable for running most power-sensitive appliances, including your laptop. It has an auto shut-off sensor when the oil is low. It has the following outlets;
- A single 120 volts 30A RV outlet
- Dual 120 volts 20A household outlets
- 12-volt DC automotive-style outlet
- Double USB adapter
With the advanced inverter technology, the unit has a smart Economy Mode that helps lower the electrical load, deliver noiseless operations, lengthened engine life, and recommendable fuel economy. At 23 feet away from your house or camping, the generator produces a 59 dBA noise level.
This is a low noise level that will not interfere with your conversations. When running on economy mode and when the unit is at 25% load, the noise level goes down.
The unit features both a recoil starter where you pull a cable to start and an electric start system.
It also has a Cold Start Technology that guarantees you an effortless start during the cold weather.
This unit is CARB compliant, and EPA certified. It will generate a decent amount of power for your domestic and outdoor events to use and operate quietly. It is also user-friendly and reliable.
- It has a Cold Start Technology that will give you an easy time to start the unit in cold weather.
- It comes with three years warranty period and unlimited customer support.
- It is a compact and portable design, suitable for outdoor events.
- It is relatively quiet when operating from 23 feet away.
- Some customers consider it to be expensive.
- It does not support remote starting.
WEN DF475T Dual Fuel 120V/240V 4750-Watt- Affordable
Second in place of the best dual fuel inverter generators is this WEN generator. This is a quality and affordable dual fuel generator from WEN. It has a fuel switch where you can choose to run it either on gasoline or propane, depending on your preference.
It has a 4-stroke 224cc OHV engine powered by an electric start with a peak-up wattage of 4750 watts and 3800 running watts when it is running on gasoline. The unit produces a noise level of about 69 dBA; this is the lowest possible noise level for this model.
In a full tank, the generator can hold 4 gallons of fuel, providing a maximum of 11 hours run time when it is 50% loaded, the average fuel consumption of 0.36 gallons per hour.
The run time is sufficient to cater to your power needs when tailgating or in need to power your domestic appliances, including refrigerator, TV, sump pump, and several power tools in a job site.
On propane, the unit produces 4350 starting watts and sustains 3500 running watts powering your project for 7 hours. With this unit, you can also power your RV.
The unit features;
- Double 120 volts GFCI receptacles (5-20R)
- A single 120V/240V NEMA 30A twist lock
- A 12V DC plug (cigarette-lighter-style)
- A voltage selector allows you to switch from 120V to 240V and vice versa, depending on your power needs.
- A fuel gauge that offers convenient means of checking the unit’s gas level
- The spark arrestor feature makes it safe for use even in the forest.
For portability, this generator can easily be transported thanks to its folding handles and never-flat wheels. However, at 105.8 lbs, the unit may be heavy for one person to carry by themselves.
You will be provided with a 47-inch LPG hosepipe for quick connection to a propane tank.
As a WEN product, this dual fuel generator comes with a warranty period of 2 years and lifetime customer support. The generator is EPA and CARB compliant.
- With its power output, this is an affordable dual fuel generator.
- Supports electric start; you only need to turn a key.
- It has GFCS outlets.
- If noise is one of your points of concern, at 69 dBA, WEN DF475T is noisier when compared to other units of its power range.
- It has a relatively high consumption rate of 0.36 gallons per hour than other models of a similar power range.
Champion Power Equipment 100574 4000-Watt- Lightweight
It comes with innovative technology and design fronting it as one of the most advanced dual fuel inverter generators in the market. This model comes with a fuel selector dial that helps you to switch between gasoline and propane.
With a 224 cc Champion engine, this unit can generate a startup wattage of 4000 watts and 3500 running watts when being powered by gasoline.
With a full tank (capacity 2.9 gallons) of gasoline, this generator can run for a maximum of 14.5 hours when it is 25% loaded. At the same load (25%), the unit can serve you for up to 18 hours when running on a 20-pound propane tank which produces a starting wattage of 3600 and maintains 3150 running wattage.
With a run time of 14.5 and 18 hours, depending on the fuel you will be using, this generator will keep your electrical appliances, including microwave, air conditioners, refrigerators, and space heaters, running for long.
For outdoor events, this generator will be your portable power source. It also allows parallel connectivity n case you have more power demand.
This model has an oil capacity of 0.6-quart and an auto shut-off sensor when the oil is low. This protects your engine from wearing out in case it has no oil.
When set to run from 23 feet away, the generator operates at 64 dBA; this noise level is louder than a normal human conversation.
On the positive side, this unit produces clean power (not more than 3% THD), safe for running all your sensitive electric appliances. It has also been seen as one of the best inverter generators.
The generator has an easy recoil start that utilizes Cold Start Technology to start the generator when the weather is cold quickly. The outlets in this unit include;
- A single 120V 30A RV (TT-30R) outlet
- Double 120V 20A domestic outlets (5-20R)
- A single 12V DC automotive-style outlet with a USB adapter to create dual USB ports on this outlet.
- It has long-running hours.
- It has an economy mode feature making it fuel-efficient.
- It is lightweight (82.2 lbs) considering the range of power it produces, hence portable.
- Allows you to increase power output by making parallel connections.
- It is relatively noisier
- It does not have an electric start.
- No data center; you can’t tell the status of the generator when it is running.
DuroMax XP12000EH Dual Fuel Generator-12000 Watt- Best choice of domestic power back up
If you are looking for a powerful and versatile dual generator for your domestic power back up, Duromax XP12000EH is the perfect solution. The generator is powered by a 457 cc 4-stroke engine with dual-fuel technology. This is a powerful engine that can handle heavy-duty power tools and high voltage home appliances.
With dual-fuel technology, you can use either power it with gasoline or propane. The gasoline fuel tank has a capacity of 8.3 gallons. When running on gasoline and at a full tank, Duromax XP12000EH can produce a surging wattage of 12000 watts and run on 9500 watts.
Running it on propane gives it a peaking wattage of 11400 watts and 9025 running watts. When the gasoline fuel tank is full, and the unit is loaded 50%, it can run for 8.83 hours and 7.2 hours when running on a 40-lbs propane tank while maintaining the same load.
When running on a quarter load, the unit produces a 74 dBA noise level, which is relatively high but expected from such a big machine.
While this is a big generator measuring 30 × 29 × 26 inches and weighs 224 pounds, this generator is still portable.
It has solid-fill wheels for easy moving and a full metal frame that can be used as handles. You power it on using the recoil start method or go for the electrical start option.
This generator will lower fuel consumption with an idle control feature when it is not in use by lowering its RPMs. It is, therefore, suitable for projects where power is used intermittently.
It also has a low oil shut-off sensor, which means the generator will automatically power off when the oil is low hence protecting the engine from damages attributed by running with no oil.
With the Duromax MX2 technology, you have the option of operating the generator at 120 volts and 240 volts concurrently or operate it at 120 volts only. Suitable to be used with RVs.
There are several outlets available on this model, including:
- Double 120V households GFCI receptacles
- A single 120V 30A twist lock receptacle
- Single 240V 30A receptacle
- One 240V 50A receptacle
- A 12 DC charging port and voltmeter.
The outlets available on this model are enough evidence that this is a heavy-duty dual fuel generator.
- It is built with high-quality materials making it appropriate for a home power backup and a power source on a construction site.
- It is a powerful tool, and a noise level of 74dBA is reasonably allowed considering the amount of power it produces.
- Verified customers confirmed it comes with a charged battery, ready for an electric start.
- Most verified customers complained of poor handling during shipment, which leads to the delivery of faulty units. It is an expensive unit, and it should be shipped and handled with care.
iGen4500DF Dual Fuel Inverter Generator by Westinghouse- Low noise
This is a dual fuel inverter generator that has an output of 120 volts. Using propane as fuel, this model can produce a starting watt of 4050 and maintains a running wattage of 3,330 rated watts.
When running it on gasoline, it produces more power: a peak up wattage of 4,500 watts and a running wattage of 3,700 watts.
With the power output from this generator, it can power your kitchen stove, electric heater, dryer, water heater, lights, and other smaller electric appliances.
The Westinghouse iGen4500DF fuel tank can carry up to 3.4 gallons of fuel. With a full tank of gasoline, the generator can run for 18 hours. It translates to an average consumption ratio of 0.19 gallons hourly. When using propane of 20-lbs tank, it can power the generator for up to 14 hours.
This model consumes propane at the rate of 0.34 gallons per hour. If you’re buying this generator for your power backup, a running time of 14 hours when using propane or 18 hours on gasoline is sufficient to power your house before power is restored the following day. Or before you refill the tank.
This generator produces a pure sine wave with a THD (total harmonic disruption) of not more than 3%. This THD level is ideal to power the most sensitive electronic appliances in your home or your excursion.
The generator has AC outlets that comprise a single 120V 30-A (TT-30R) and dual 120V 20-A (5-20R) receptacles to power your house or electrical appliances. It also comes with duo 5 volts USB ports that can recharge your tablets, smartphones, and camera.
The unit comes with an LED data center where you can easily monitor the fuel level, power output, remaining running time, and lifetime run hours. You can periodically check on the data center to tell the unit’s status when it is running.
If you are looking for a portable dual fuel generator, Westinghouse iGen4500DF comes with a 5.5-inch wheel kit that helps you move this 98 lbs unit.
The generator is enclosed in a design of 24.5 × 17.5 × 20.5 inches’ case. You will not struggle to carry this unit for an outdoor event.
On a noise level, the unit produces 52 dBA, which is relatively quiet. On Amazon, Westinghouse iGen4500DF has an average rating of 4.5 out of 5, with most customers express satisfaction with the low noise level, portability, and performance.
- The generator has an electric and remote starting mechanism
- The manufacturer offers three years warranty period with lifetime technical advice and support.
- It has an LED data display screen that shows you the performance and status of the generator.
- With a 52 dBA noise level, this is a relatively low noise output.
- Compared to its size, 98 lbs is relatively heavy.
- Its fuel efficiency is comparatively low.
Westinghouse iGen4500DF is a solid dual fuel generator suitable for a power back plan, outdoor events, and RV users.
DuroMax XP4850EH Generator-4850 Watt- Easy to power on
It is a powerful and yet user-friendly generator that allows you to choose between gasoline and propane. It runs on a 210cc OHV engine that generates high voltage power to run your home appliances and heavy-duty power tools at a working site.
When running on gasoline, the unit can hold a maximum of 3.96 gallons producing a peaking wattage of 4850 watts and run at 3850 watts. With a 50% load, this generator can run for 10 hours on propane, translating to a consumption rate of 0.4 gallons per hour.
With a 20-lbs propane tank, it can generate 4608 starting wattage and maintain 3658 running watts. It can run for about 9 hours when it is half loaded; this is a consumption rate of 0f about 0.52 GPH.
The unit can power your lights, refrigerator, air conditioner, among other heavy voltage appliances. With a THD level of less than 12%, this unit is not ideal for powering your sensitive electronics.
With the MX2 technology, this unit allows you to choose your choice voltage; you can choose to operate it at 120V only or 120V and 240V concurrently.
If you are an outgoing person, it’s suitable for RVs. With an electric start, it is easy to power on this unit when you need it.
The low oil shut-off feature protects your internal generator components from damages when the sensor senses the oil is low. Besides this feature, it also has an indicator light that shows oil levels.
On the power panel, the generator has a wide selection of outlets that you can utilize; they include:
- Duo 120V 20A (5-20R) GFCI (AC outlets)
- Single 120/240V 30A (L13-30R) (AC outlet)- transfer switch ready in a power black-out.
- 12V 8A DC outlet- for charging your batteries with ease
XP4850EH also has a circuit breaker for overload protection.
At 122 pounds, this generator is relatively heavy. However, with its folding handles and wheel kit, you can move it with ease. The generator is EPA certified and CARB compliant.
- It has an electric start for easy powering on.
- It comes with a fuel gauge and voltmeter for easy output power monitoring.
- With a noise level of 69dBA, it isn’t quiet.
- Several verified buyers complained about the three years’ warranty period, which does not cover everything. You have to cater for the shipment of any accessory under the warrant and, in some instances, plan how you will fix it. It is an affordable dual fuel generator that you can invest in.
Sportsman GEN4000DF-Multiple AC outlets
Whether you are looking for a generator to supplement your home in the event of a power outage or you are a camp freak, sportsman GEN4000DF generator is a fascinating deal for you. As a dual fuel generator, it can either run on gasoline or propane.
The unit can power your home lightings, refrigerator, heating, and cooking equipment during power failures. You can also use it to power your construction tools and other outdoor events.
With a fuel tank capacity of 3.6 gallons, it can generate a running wattage of 3500 watts with 4000 peaking wattages when it is gasoline-powered. It can achieve 3600 starting watts and 3100 running wattage when running on propane.
It can run for 10 hours when operating on full tank gasoline and has a 50% load; this is a rate of 0.36 GPH. It can operate for 12 hours on the same load when it’s powered by a 20-lbs propane tank, with a consumption rate of 0.39 GPH.
It has a recoil start feature and has a rating of 96 dBA, which is relatively noisier.
To power your house and other needs, the Sportsman GEN4000DF has 5 AC outlets and a single DC outlet:
- Four 120V outlets
- Single 120V 30A RV ready outlet
- 12V 8A DC outlet- ideal for easy batteries charging
With the open frame design measuring 24.5 × 17 × 16.5 inches and 90 lbs weight, you can move it to different places. You don’t have to worry about its portability. With a viewable voltmeter, you can easily tell the power output at any time the generator is running. It also features overload protection (circuit breaker) and a low oil shut-off sensor. With a spark arrestor feature, it is convenient to use in a forested area.
- It is a budget dual fuel generator.
- Has multiple AC outlets that you utilize concurrently.
- It is user-friendly and has an option of green environment usage hence safe for the environment.
- It has a one-year warranty period. Considering its power output and other generators in its range, this is not convincing.
- It is not CARB compliant.
- Some verified customers from Florida complain of having had to buy extra items to operate it.
Sportsman GEN4000DF is a robust dual fuel generator that is EPA-approved. However, it is not CARB compliant hence cannot be sued in California.
Champion 100297 8000-Watt Dual Fuel Portable Generator- Light weight
This is a powerful 8000-watt generator suitable for large households, powering big outdoor events, food trucks, and construction companies.
With an electric start feature, this generator has a 459cc engine that runs on either gasoline or propane. Easy electric start mechanism even in cold weather thanks to the Cold Start Technology used in this unit’s assembling.
You can also power it on with a conventional pull mechanism. With an Intelligauge feature, you will have an easy time monitoring the voltage, runtime hours, and hertz. With the low oil shut-off sensor, the engine will not suffer damages because of running on low fuel.
With the patented fuel selector switch in this model, you can conveniently switch between gasoline and propane.
This unit can generate 10000 peaks up watts and run at 8000 watts for eight hours when the 6.0 gallons’ gasoline tank is full and at 50% load rating at 0.75 GPH consumption level.
When powered by a 20-lbs propane tank and at the same load, this generator can produce 9025 peak-up watts and a running wattage of 7250 watts and is bound to run for about five hours 0.94 GPH propane consumption rate.
It has a noise rating of 74 dBA, noisier than a dishwasher. For protecting the unit from overloads, it has an in-built surge protector -Volt Guard.
The control panel has six AC outlets to power your needs.
- Four 120V 20A (5-20R) GFCI (protected households’ outlets)
- 120V/240V 30A (L14-30R) outlets
- 120V 30A (L5-30R) outlet for a simple RV connection.
This model has a transfer switch ready; you can easily power your house by connecting it to the breaker box in case of a power outage. Additionally, this generator does not produce clean power; it has a THD of between 12% and 20%, its therefore not suitable to power sensitive electronics.
Measuring 27.8 x 28.7 x 26 inches and a weight of about 210 pounds, manually lifting this generator can be challenging. Its movability is eased by the presence of folding handles and a wheel kit.
- Considering its power output, this is a budget dual fuel generator.
- It has GFCI protected outlets.
- It has a safety fuel –selector switch.
- With the Intelligauge, you can monitor the power output and maintenance interval with ease.
- Compared to other models of similar ranges, this unit has a low run time.
9. Pulsar PG10000B16- Fuel efficient generator
It is one powerful portable generator with dual fuel capabilities today, ideal for home use, job site, and outdoor activities. It runs on a robust 420cc 4-stroke OHV engine which starts on a push to the electric push-button. It also has a conventional pull start mechanism.
With the switch and go technology in place, you can comfortably switch between your fuel sources that are between gasoline and propane. It has an auto low oil shut-off feature and a circuit breaker to protect it from overload risks.
This unit comes with a fuel tank size of 6.6 gallons. It can generate a starting wattage of 10000 watts and run at 8000 watts when running on gasoline. When it’s running on propane, it has a peaking wattage of 9000 watts and maintains 7000 running watts.
When the gasoline tank is full (6.6 gallons), it can run for 12 hours when it is 50% loaded, a consumption rate of 0.55 GPH; this is one of the most extended run times you will find in the market. It can run for 9 hours at the same load when being powered by a 20-lbs propane tank.
This model has multiple outlets, including 6 AC outlets and 1 Dc outlet;
- Two double 120V 20A (5-20R)
- 120/240V 30A (L14-30R) outlet-transfer switch ready for connection to your home in case of a power outage.
- 120/240V 50A (14-50R) outlet
- 12V 8A outlet for easy battery charging.
With a weight of about 209 pounds, lifting this generator can be challenging. However, its open frame design measuring 28.5 × 21.8 × 23 inches allows this unit to above the ground. The presence of folding handles and wheel kit eases its movement when it’s on the floor.
- Has one of the highest run time in the market
- It is a fuel-efficient dual generator.
- High power output and seven outlets mean you can power several devices concurrently.
- It is an expensive but worth investment
- According to several verified buyers on Amazon, it does not produce clean power for sensitive electronics.
10. Firman H03651 Hybrid Series
While Firman may not be a famous company, the Firman H03651 hybrid series is a dual generator worth considering. With three years warranty period, you are sure of the quality of this product. Ideal for both outdoor activities and as a home backup plan.
This model runs on a Max pro-Series 208cc engine that delivers 120V can run on either gasoline or propane; the choice is yours to make. You can start this engine by going for the conventional pull-start mechanism or the electric starter. With a rated noise level of 67 dBA, the unit is relatively less noisy compared to a normal human conversation.
With a 5 gallons’ fuel tank capacity, this generator can deliver a peak wattage of 4550 watts and maintain a running wattage of 3650 watts. When on propane, it can produce 4100 peak watts and 3300 rated watts.
The generator can operate for 14 hours at a full tank when it is at 50% load and running on gasoline, a consumption rate of about 0.36 GPH.
While at the same load but powered by a 20-lbs propane tank, the unit can run for 11 hours, translating to 0.43 GPH. It has a higher THD which is less than 25%; you can not power your sensitive electronics using this generator.
However, it has an automatic voltage regulator, which guarantees the safety of your electronics.
The outlets in this unit are covered to ensure no trapping of dust and other debris. The four outlets are;
- Double 120V 20A (5-20R) GFCI receptacles
- 120V 30A (L5-30R) outlet
- 120V 30A RV ready outlet
The non-flat tires and foldable handle make it easy to move this 119.5 lbs unit measuring 24.7 × 21.8 × 21.6 inches. The design is to make this model ideal for tough environments.
Check on the status of the generator by checking on the convenient meter. The low oil shut-off sensor ensures your generator does not run on low oil. It also has an in-built circuit breaker to protect the unit from overload.
- It has the highest run time in this review.
- The outlet ports are covered to protect it from dust and other particles that may hamper its functionality.
- Three years warranty period is adequate.
- Some verified buyers on Amazon complained that the generator needs to run for a while before loading it.
- Several customers also complained that the product was delivered faulty.
Factors to Consider Before You Buy any of the best Dual Fuel Inverter Generators
- Look at the generator’s size: The size of the generator you are buying should be compatible with the amount of power you need and your storage space. The amount of energy you need can be determined by looking at the appliances you need to power.
- The noise level: Generators running on gasoline are more likely to be louder. Where you are going to place the generator will determine the amount of noise that you will perceive.
- What is your budget? The cost of generators will depend on their sizes. Be sure to get the right generator for your budget.
- Portability: If you need the generator for outdoor activities, then it should be easy to transport. If it is for home or office use, you don’t need to worry about its portability.
Frequently Asked Questions
What is the most efficient fuel for a generator?
Diesel is the most efficient fuel to power your generator. However, it is not common when compared to gasoline.
What fuel does an inverter generator use?
Inverter generators consume gasoline or propane as their source of fuel. One can also read to understand how does an inverter generator work.
What is the quietest dual fuel generator?
Are dual fuel generators any good?
Yes. You can switch from gasoline to propane, depending on what is at your disposal.
How long will a 20lb propane tank run a generator?
It will depend on the engine size of the generator and the load size too. In our review, Champion Power Equipment 100574 4000-Watt will run for 18 hours when it has a 25% load.
Does Yamaha make a dual fuel generator?
Yes. Yamaha Premium dual-voltage model# EF12000DE is a dual fuel generator.
Does predator make a dual fuel generator?
Yes. It has a dual fuel kit that permits you to either run it on natural gas or propane (on low pressure).
Is it better to run a generator on propane or gas?
Propane is cheap to acquire than gasoline. However, it has low energy density than gasoline. Propane is also good for the environment and for the generator itself because it burns cleaner than gas.
Is ethanol-free gas better for generators?
Only when the gas has 10% ethanol and below. Otherwise, it’s advisable only to use non-ethanol fuel on your generator.
Will premium gas hurt my generator?
Yes. If your generator has a small engine. For the best performance of your generator, look out for clean and unleaded gasoline.
Who makes the best dual fuel generator?
Westinghouse is among the top manufacturers of the best dual fuel generators.
Is a dual fuel generator worth it?
Yes. Dual fuel generators are effective. They offer more power and run for long hours.
Which generator is better, Champion or Firman?
They are typically the same. However, Champion is a more reputable generator manufacturer than Firman.
Is an inverter generator better than a regular generator?
Yes. Inverter generators are more energy-efficient compared to conventional ones.
Can an inverter generator run a refrigerator?
Yes. Inverter generators are available in different power capacities. Some can run generators, and others cannot. One that can produce 120V AC can power a generator.
How does a dual fuel generator work?
They use two types of fuel, mostly either gasoline or propane. They also come with a fuel selector switch that allows you to choose the source of energy you want to use. If you are out of gasoline, you can use propane and vice versa.
Can you run a dual fuel generator on natural gas?
Not unless you have a fuel conversion kit, it will not be possible to run a dual fuel generator on natural gas.
What are the shipping options for Inverter Generators?
Provided they are EPA and CARB compliant, all types of inverter generators can be shipped to your place of residence.
What are the advantages of the best dual fuel generators?
- You can use different types of fuel. Choose from what is available or what you want to use.
- Dual fuel generators are long-lasting when compared to traditional generators.
- They can automatically switch fuel when one is depleted.
- They are more environmentally friendly than the traditional ones.
Why only dual fuel portable generators? Aren’t there any units that run on propane only?
Dual fuel portable generators are better because of the ability to switch from one fuel to the other. Otherwise, there are different models of generators that only run on propane.