What Portable Generator Size Can Run a Furnace?

The furnace enables you to keep your family warm and to ensure that everyone, during the winter is comfortable at home.

In places that are prone to power failures, a simple blackout can cause your boiler to stop working until power is restored, which can take hours or days. To prevent casualties, a portable generator can be used to operate a furnace.

Below we made mention of the best generators to run a furnace in 2021 and beyond.

Without Further ado;

Best Generator To Run A Furnace – Our Top Picks


Honda EU3000iS


EU3000iS is one of those generators from Honda that are equipped with advanced technology and can work very quietly and efficiently. You can use it not only for home and camping but also for running your air conditioner.

If you have a full gas tank, it can run straight for 7.2-20 hours, but it certainly depends on the load. If you want to use it with your motorhome, it can also be an efficient unit that you can carry with you.


  • Emergency source of power for motorhomes with additional back up for ACs up to 13500 BTU
  • Generates a noise level of up to 58 dBa, which is completely negligible
  • It has a recoil start option
  • With 3.4 gallons of fuel, it can run for a maximum of 20 hours
  • The great eco-throttle feature improves fuel efficiency
  • Advanced inverter technology ensures that all of your devices are powered reliably and securely to protect them from damage
  • It can be connected to another one of these generators in parallel to get more power up to a maximum of 6000 watt
  • Supplied with a 12 V DC socket
  • Low oil level indicator ensures that the engine is switched off when the oil level is low
  • Additional protection for your household appliances in the event of an overload


  • Portable
  • Compact design
  • Easy to lift and install
  • The finest noise reduction
  • Comes with an ignition system, throttle valve, and fuel valve


  • Pretty expensive in its class
  • The duration is not that long

Champion 4,000-Watt



The Champion 4,000 Watt Inverter Generator is highly portable, so even if you move from one city to another, it’s not a problem to carry it around with you to your new home. It’s equipped with a kick start device and a wireless connection.

You can conveniently operate it remotely from your mobile phone, but you must be within 80 feet of the generator. This generator can easily run 12 hours at a time with no problem if you have fuel at full capacity in the tank.

It’s also supplied with a steel frame that allows the generator to operate in quiet mode. Unlike many other generators, this generator can only produce a noise level of 68 dBa, which is negligible if you are in a dense residential building.

Apart from air conditioning, you can easily operate sump pumps, televisions, power tools, etc. while you’re experiencing a power outage in your area. Apart from an additional RV connection, it has 2 sockets with 120V each. It also has a monitor that informs you about the voltage, operating hours, hertz, heating, etc., and the oil shortage sensor shows you when to fill the tank or stop the appliance.


  • With a 196cc engine and battery, you can start your machine easily.
  • It’s supplied with an ignition switch equipped with Cold Start Technology so that the machine remains in operation even in the cold season.
  • If you’re within 80 feet of the generator, you can easily control the stop and start button from your smartphone using the built-in mobile connection that is available with the generator.
  • It has a maximum start power of 4000 watts and a running capacity of 3500 watts, which is enough to power your home for at least 12 hours, and if you add the fact that it doesn’t make any noise above 68 dBa.
  • 4 outlets are available. 2 sockets with 120V, 30A power source, and 2 sockets with 120V 20A power source.
  • It also includes a built-in surge protector that protects your devices from any kind of overload problems.
  • 3 years warranty from the manufacturer


  • Start and stop remote control
  • Water-resistant to a certain degree
  • Supplied with folding handle
  • Includes additional RV connectors
  • Meets the standard of CARB
  • You can operate the device for 17 hours without overloading or overheating problems
  • 3 years guarantee


  • The oil change could be a little difficult due to the position of the dipstick.

Westinghouse iGen2200 Inverter


The engine and fuel efficiency of the Westinghouse iGen2200 is very impressive. This model has an average large of 1.2 gallons fuel tank but is sufficient for an impressive 12 hours runtime at a quarter load.

Another advantage is that a parallel switching device can be connected, which gives you a whopping 7200 watts of operating power and 8800 watts of the peak, which is sufficient to run all the important appliances in your household such as a furnace, air conditioning, water heater, and refrigerator.

However, parallel capabilities are not limited to this model alone. You can connect your iGen2200 to other Westinghouse models such as the iGen2500 to increase wattage and amp available.

All this power comes with very little noise. The noise power is measured at only 52dB. All of this is eco-labeled because it’s both EPA and CARB compliant. Westinghouse stands behind their work, which is reflected in the three-year warranty and free technical support forever.


  • Running Wattage: 2,200 watts
  • Start Wattage: 2,500 watts
  • Running time: 12 hours at 1/4 load
  • The capacity of the tank: 1 gal
  • Noise Level: 52dBA
  • Weight: 48 lbs


  • Powerful
  • Compatible in parallel
  • Long-running time for a given tank size
  • Very quiet
  • EPA and CARB compliant


  • Several users have reported leaking tanks

Firman W03081 Inverter

The best part of the Firman 3000 Watt model is its portability. It is equipped with strong wheels and an easy-to-grip handle, which makes transporting this 97-pound inverter generator easy and convenient.

With a running power of 3000 watts and a surge power of 3300 watts, its performance is also very valuable for its price. The engine is powered by a 1.8-gallon fuel tank, which is a little bit larger than average with only an average running time of nine hours.

The extensive control panel on the side of this generator is an interesting feature of the model. It has a light indicator, switches, and any type of sockets, all of which are protected from dirt thanks to the cover already fitted.

A final plus point is that FIRMAN supplies this inverter generator with a range of accessories such as oil, wrench, and a funnel.


  • Running Wattage: 3,000 watts
  • Starting Wattage: 3,300 watts
  • Running time: 9 hours at 1/4 load
  • The capacity of the tank: 1.8 gal
  • Noise Level: National part certified
  • Weight: 97 lbs
  • Produces clean electricity with less than 3% THD, has an eco-mode for maximum efficiency, and comes with a 3-year warranty.


  • Maintenance accessories included
  • Good performance
  • All controls in one place for easy operation


  • Average running time for tank size


Predator 3500 Inverter Generator

The Predator 3500 Watt Inverter Generator runs on a 212cc OHV engine with air cooling as standard. This engine is responsible for the impressive runtime of up to 11 hours at a quarter load.

This model also compatible with a parallel set, making it a great option for motorhome travel. It’s equipped with a 30 amp RV adapter to make installment easier for you.

The LCD screen allows you to keep an eye on all the variables and monitor the power consumption, with the indicator lights showing the output and the overload warning. Although it doesn’t have an automatic shutdown when fuel consumption is low, it does have a warning light when it’s time to refuel.

Finally, it is a discreetly quiet model valued at 57 decibels. This is quiet enough to carry along for camping without inconveniencing the neighbors and wildlife.


  • Running Wattage: 3,000 watts
  • Starting Wattage: 3,500 watts
  • Running time: 11 hours at 1/4 load
  • The capacity of the tank: 2.6 gal
  • Noise Level: 57dB
  • Weight: 99.2 lbs
  • Includes a digital LED screen that shows overload, lack of oil, and power.
  • It also has 4 attached wheels for transport and electronic overload protection.


  • Long-running time
  • Parallel compatibility


  • No fuel gauge
  • Users report difficulties in understanding the manual.

How many watts does a furnace need?

A gas-fired, home furnace with forced air usually requires a small amount of electricity to ignite and work in your home. Most gas furnaces use less than 600 watts of electricity or less than half of a typical 15 amp circuit.

The furnace uses this small amount of electricity to drive the blower or fan part of the furnace, which circulates the air in the house and also drives the suction fans to force the exhaust gases safely out of the house.

When it comes to buying a portable generator, there are some things to consider before buying the first generator you see. The most important thing is that you need to find out is how many watts your furnace uses.

Most household furnaces consume about 600 watts depending on the manufacturer your furnace may use more or less. The easiest way to find out exactly how many watts your furnace consumes is to consult the manual or the manufacturer’s website to find out what wattage is required.

This could also be found on the manufacturer’s label at the back of the furnace. Once you’ve figured out how many watts your furnace needs, you’ll want to purchase a generator that supports at least twice the amount of wattage your furnace needs to avoid overloading your generator.

Most generator running times are measured at a power consumption of 50%. So if you are trying to get the most runtime out of your generator when operating your furnace, look for a generator that can deliver twice the wattage require by your furnace.

In this way, you can also switch on the other important appliances or equipment while your furnace is running. This can include a mobile phone charger, refrigerator, or other devices needed to help you get survive your next power outage.

How much power do I need?

A great way to maximize the efficiency of your generator is through power management. The use of power management can help you do this:

  • Use a smaller, cheaper generator to meet your requirements
  • More efficient use of the generator

Power management works based on a simple concept: it is not necessary to supply power to everything at the same time. Switching from one device to another helps to minimize the amount of energy required.

Think about it:

  • What is the most important thing to power?
  • Must it be operated continuously?
  • Don’t try to run everything at once.

For example, suppose you use a generator to provide your house with electricity. You want to operate some lights, a fridge, a furnace, a television, and a microwave.

Appliance                     Starting Wattage           Running Wattage

Fridge                             1600                            200

Furnace (1/4 HP fan)      1600                             600

5 Lights                           300                              300

Television                        300                              300

Microwave                      1500                            1500

Total                                5300                            2900

If you only consider the total watts, you might think that you need a 5300-watt generator to power your home. But that’s not the case. Start appliances with high start wattage at different times.

When you start the fridge and the furnace at different times, you don’t need 3200 watts of power – only 1600. If you only use an appliance occasionally for short periods, let it run alone.

Turn off the refrigerator and furnace for a few minutes while using the microwave – a little compromise like this saves you 1500 watts. If you don’t mind turning off the lights and TV, you can use a smaller model. But if you don’t want the stress, go for a bigger generator.

Let’s look at our example again.

Continuous Power requirement

Running refrigerator                   200

Running furnace                         600

5 lights                                        300

Television                                    300

Total                                            1400


Occasional electricity demand

Starting the refrigerator              1600

Starting the furnace                    1600

Microwave                                   1500

Max                                              1600

In this case, a 3000-watt generator would be able to operate everything without any problems. And you don’t have to sacrifice anything.

Of course, you can get by with just 1600 watts – if you’re ready to run the furnace and fridge at separate times and turn off the TV and lights when you start using one or both of these larger devices


To recap, the generators we recommend for powering furnaces are the following:

  1. Honda EU3000IS 3000W
  2. Champion 100302 4000-Watt
  3. Westinghouse iGen2200 Super Quiet
  4. Firman W03081 3300/3000 Watt
  5. Predator 3500 Watt Super Quiet

If you have read thus far then I believe you know the perfect generator size to power a furnace in your home. To know more about appliances generator can safely power, check out the articles mentioned below;

Generator size to power an Ac

Generator size to power a TV set

Ideal Generator size for refrigerator

How many volts should a generator put out?