Planning to buy a backup generator to manage your power needs during prolonged power outages?
The first thing you need to do for calculating the generator wattage is list the appliances you will run by using it.
And one major household appliance that you need to run is the refrigerator.
Is running a refrigerator on a generator safe?
As long as you have picked the right generator for the refrigerator in terms of power capacity, it’s perfectly safe.
You need around 2,000 starting watts and 200 running watts to run a refrigerator on a generator.
How Much Generator to Run a Refrigerator?
There’s one major difference between a refrigerator and other appliances
The main component of a refrigerator or a freezer is an electric motor that runs the compressor. The same is the case with other appliances like air conditioners, grinders and mixers, and vacuums that have motors or compressors.
The point is, any device that depends on an electric motor will need a large amount of current to start up.
Allow me to explain.
Basically, the motor consists of a rotor and a stator. Now, the emf induced in the rotor depends on the Slip, which is the difference between rotor and stator speed.
Slip (s) is measured by the following formula:
s = (Ns − Nr) / Ns
Here, Ns =speed at with the magnetic field of the stator rotates and Nr= speed at which rotor rotates
Since the rotor of a motor is stationary when it starts, Nr is zero. So, the value of slip at this point is 1, which is the maximum.
The emf generated at the rotor (Er) is given by the formula Er = sEs, where Es is the stator voltage.
So what’s it all about?
As the value of s is 1, the emf generated at the starting point is the highest. Since the rotor offers minimum resistance to the current at this point, the current flowing through the motor is very high.
Also, the power drawn by the motor at this stage will also be much higher. The starting watts can be 4 to 8 times higher than the normal power requirement.
However, this higher power draw usually takes around 2 to 3 seconds and rarely exceeds 10 seconds even for larger appliances.
This is the cause behind the high starting wattage for refrigerators. The actual value will depend on the size of the motor, its energy efficiency, and other factors.
And remember: a refrigerator with a higher energy star rating will consume fewer starting and running watts.
As the rotor gains speed, the current decreases and the wattage requirement drops to the standard running watts.
Large older refrigerators can have starting watts of more than 2000 watts. On the other hand, the running watts can be around 700-1000 watts.
In general, the power consumption of modern refrigerators is listed below.
- Large refrigerators- 1500-2500 starting watts and 200-400 running watts
- Medium size refrigerators- 700-1000 starting watts, 100-250 running watts
- Standard Mini Fridge- 200-300 starting watts, 50-75 running watts
- RV refrigerators- 80-120 starting watts, 40-50 running watts
Quite simply, while choosing a generator to run a refrigerator, the high starting watts should be considered.
For example, for a large refrigerator, a generator that can deliver around 2,500 to 3,000 starting watts should be an ideal choice. Make sure to check the user manual to find the exact value of the starting watts for the unit.
What if the numbers aren’t available?
As a rule of thumb, you can multiply the running watts by a factor of 4 to estimate the starting watts for running a refrigerator on a generator.
If you’re planning to run a freezer on a generator, keep in mind that the wattage for modern freezers can vary between 80W to 900W depending on the capacity.
Obviously, the refrigerator isn’t the only appliance the generator will run. So, the total wattage will depend on the power requirement of all the appliances put together.
So, how should you calculate the right generator size for your home?
This demands a separate discussion.
Conserving Fridge Generator Power
Keep in mind that frequent starting and stopping can stress a motor. This is due to the mechanical stresses generated in the rotor cage and heat generation.
In reality, motors are designed to handle the high starting watts but frequent starting can reduce their life expectancy. So, it’s best that you reduce the number of times you start and stop a refrigerator as best as you can.
Picking a generator that doesn’t supply the necessary watts will fail to run the refrigerator. It will also increase the thermal stresses on the compressor motor. In addition, it can also damage the thermostat inside the refrigerator.
Beyond that, a low wattage generator will also trip the overload circuit when used to power up a large refrigerator. In other words, the generator will shut down.
Bottom line: never force a generator to supply more power than its rated watts.
That said, you can’t run your generator for extended periods of time during a prolonged power outage. Any generator will need a break after hours of operation.
However, you can conserve your generator fuel supply during a power outage by using the refrigerator’s ability to keep cold even without power.
With the door kept unopened, a refrigerator can keep the food cold for about 4 hours. Smaller refrigerators will be able to keep things cool for about 2 hours without power. Keeping the door closed will help in preserving the temperatures.
Likewise, a fully loaded freezer can keep the interior temperatures cold for 48 hours without power if the door remains unopened. If the unit is half loaded you can expect the temperatures to remain cold for around 24 hours.
This is because, with more mass, the time taken for heat transfer is higher. That means if your area has frequent power outages, stuffing the fridge with more items is a good idea. You can also use dry ice during a power outage to keep the refrigerator cool for longer periods.
In addition, keeping ice packs, or gel packs in the freezer and plastic water bottles are effective ways of reducing heat transfer. Keep the fridge in a cool dark place away from heat sources to prevent it from working harder to preserve the inner temperature.
Running the refrigerator intermittently will help you conserve generator fuel. But it’s best to keep the refrigerator running continuously as much as possible.
That way, you won’t be risking the food getting spoiled. Also, if the generator runs on the running wattage for longer periods, the unit will not have to work hard to bring the temperature down. Thus, it will save you power in the long run.
Running Multiple Appliances
One mistake many users make while running multiple appliances on a generator is not taking into account the starting watts.
If you’re running multiple household appliances simultaneously, especially the ones with a motor, the starting watts needed will shoot up. If the generator doesn’t deliver enough power to cover that wattage, it will shut off.
There are two ways to deal with this. Firstly, you need to size the generator correctly to cover all the appliances. However, larger generators are more expensive. They also consume more fuel and are noisier.
The other way is not to run all the power-hungry appliances at the same time. Adjusting the usage pattern of appliances will help you to optimize the power consumption and reduce the power requirement. This will allow you to choose a smaller generator to run things efficiently.
Note, generators shouldn’t be run at full capacity at all times as this will reduce their lifespan. It’s best to choose a unit that offers a 15 to 20% higher amount of power than your requirements.
Once you have picked the proper power output needed for running a refrigerator on a generator, it’s time to determine the generator type. The main options in terms of fuel are gasoline, propane, diesel, natural gas, or rechargeable batteries.
When you’re running multiple appliances, you will need a generator with a high-power capacity. We suggest picking an inverter generator as it provides clean energy for power-sensitive electronic devices.
And another thing…
Inverter generators will also automatically throttle down when the power demand is less. When the power demands are high, the engine will rev up again. This provides better fuel economy than ordinary generators.
That said, you need to run these generators with the same precautions as non-inverter models.
For running a large refrigerator you’ll need a generator run by gas or propane. Or else, you can also pick a dual fuel generator if propane is cheaper in your area. Besides, propane also has a higher shelf life and doesn’t generate fumes. So, it’s easier to store than gasoline.
Since solar-powered generators deliver a relatively lower power output, they aren’t suitable for delivering the high starting watts needed for refrigerators. However, some solar-powered devices can be used with solar panels to power small mini-fridges.
Note, if you want to pick generators for your apartment, the choice is limited to battery-powered units. Since they have relatively low power outputs, they aren’t the best choice for powering refrigerators.
Running Only a Fridge
When you’re running only a refrigerator on a generator, the calculations are easier. All you need to do is pick a generator that can deliver enough backup power to cover the high starting watts of the refrigerator motor.
The problem is, the start-up watts aren’t mentioned on the label of most refrigerators. In that case, the best option is to go by the rule of thumb and make a rough estimate.
A standard 120-volt refrigerator needs no special connections. If you’re using an extension cord, make sure that it’s rated for the generator. Or else, you can install a transfer switch that makes using an external power source easier.
How Long to Run a Generator for a Refrigerator
It’s impossible to pinpoint the exact running time of any fuel-powered generator as it depends on many factors. These are the specifications of the model and the wattage. Basically, you can run a portable generator as long as the fuel tank lasts.
For standard gas-powered inverter generators, that can be between 6 to 12 hours. For propane generators, the run time is limited by the size of the propane tank hooked with the unit.
Remember to give the generator some time to cool down before refueling. Pouring gasoline into a hot engine can be risky and cause a fire hazard.
Choosing the Right Generator for a Refrigerator
We have listed the best portable generators for home use in our reviews. Among the top picks, these are the three options that are the best choices as refrigerator generators.
The Honda EU2200i is the top pick as it’s one of the best generators in the market in terms of performance and reliability. With 2.200 watts of surge power output, it’s capable of powering most refrigerators. The fuel efficiency is good enough to make it run for 6 to 7 hours on a full tank. While it’s not cheap, the “Honda reliability” ensures years of trouble-free use.
The Wen 56200i generator is a great choice when you’re looking for a portable inverter generator. With an output of 2,000 surge watts, it can power refrigerators and a few other smaller appliances as well. Moreover, it’s a budget-friendly option that offers excellent dollar value.
If you’re looking to run multiple appliances, the DuroMax DS4400E is a dependable choice that combines reliability with an affordable price tag. The surge power output is 4,400 watts and it has excellent safety features along with a user-friendly power panel.
Frequently Asked Questions
How long does a generator need to cool down?
The time required for a generator to cool down depends on a number of factors like the size, fuel type, the number of running hours, and the ambient temperature. Depending on these factors, a generator can take anywhere between a few minutes to multiple hours to cool down
How many watts to run a refrigerator on a generator?
The number of watts required to run a refrigerator on a generator depends on the size of the refrigerator and its starting watts. Generally, a 2,000-watt generator should be able to run a standard refrigerator in most homes.
Do you need a generator for a chest freezer?
Chest freezers are more affordable and consume less power than a deep freezer. Generally, they consume around 20 to 25 kWh of electricity per month. So, you’ll need to use a generator for running it during an outage.
Once you understand the basics of selecting the right type of generator, running a refrigerator on a generator is a breeze. With the right generator output, it’s perfectly safe to use a generator to run a refrigerator during a blackout.
Ideally, you should keep your generator running the whole time during an outage to power the refrigerator. However, for prolonged outages, you might need to shut it down for a few hours.
And after having picked the right generator to run a refrigerator, make sure to follow the necessary safety guidelines for running fuel generators.
Now go out there and make it happen.