When calculating how much solar power you need to run your fridge, you first need to know how much power your refrigerator uses.
Which can be tricky.
Unlike most appliances, you can’t just look at the wattage of a fridge and multiply that by the number of hours it’s on to get daily usage.
That’s because a refrigerator cycles on and off throughout the day. So it actually uses less power than indicated on the label.
In this guide, we discuss how to calculate how much electricity your refrigerator REALLY uses and how much solar power you’ll need to run it.
How Much Power Does My Refrigerator Use?
For most appliances and electrical equipment, it’s easy to calculate how much power they use.
You look at the wattage indicated on the appliance and multiply it by the number of hours it runs. If you have a 1500W space heater, it’ll use 1500Wh if you run it for an hour and 4500Wh if you run it for three hours.
You can’t do the same with a refrigerator. A 200W refrigerator doesn't consume 4,800Wh every day (200W*24hrs). It uses way less power than that.
Because the compressor cycles on and off, the fridge runs at full power for only part of the day.
There are several ways to estimate how much power your refrigerator uses.
Note that your refrigerator could consume more power than you’ve calculated depending on several factors.
If you live in a warm climate, the fridge will use more power since the compressor works harder to keep the refrigerator cool. Ditto if you open the fridge door frequently or the refrigerator stays half empty most of the time (a full refrigerator uses less power).
Older refrigerators are less efficient and will also consume more power.
Unless you’ve used an electricity usage monitor to get an accurate measurement, we recommend adding a small margin to your final calculation to make sure you plan for adequate solar power.
Say, you’ve calculated your fridge uses 1.6kWh per day. Round that up to 1.8 or 2kWh.
Now, you can figure out how much solar power you need.
What Size Solar Generator Do I Need To Run A Refrigerator?
If you are planning to use a portable solar generator to power your refrigerator, get one with enough capacity to power the fridge for at least a day.
In our example above, we’ve calculated that our refrigerator uses 1.6kWh per day. Let’s add a safety margin and use a figure of 1.8kWh or 1,800Wh.
So we need a solar generator with a capacity of at least 1,800Wh.
However, lithium solar generators do not provide 100% of their stored capacity. They typically hold back 10 or 20% to protect the battery from degradation.
Let’s say you can’t access 15% of the capacity. So in reality, you need a capacity of 2,070Wh (adding 15% to 1,800Wh) to get the 1,800Wh capacity you need.
If you want to be able to power your fridge for more than a day or you plan to power other appliances in addition to the refrigerator, get a bigger solar generator.
For campers looking to power a mini camping fridge, repeat the above calculations using your fridge’s average wattage.
For instance, a camping fridge rated at 60W probably averages a power consumption of 20Wh (60/3). If you plan to run it 24/7, it’ll use 480Wh each day (20Wh*24hrs).
A 600Wh solar generator should be enough to keep it running all day.
You can get a smaller unit if you plan to run the fridge for only a few hours each day. For instance, a small 200Wh solar generator can power our camping fridge for 8 hours.
Tip: Make sure the solar generator inverter can supply the necessary running wattage for the refrigerator. The good news is that refrigerators are generally low wattage (usually less than 300W), so even a small solar generator is up to the task.Tip: For camping and portable refrigerators, get a 12V powered fridge. Plugging your fridge into the solar generator’s DC outlet will get you a longer run time compared to plugging it into the AC outlet. That’s because the AC inverter is not 100% efficient, so there are some power losses.
What Size Solar Panel Do I Need To Run A Refrigerator?
If you want to rely fully on solar power to run a refrigerator, you’ll need solar panels that generate enough power to power the fridge for a day.
Start by calculating how much power your refrigerator uses in a day. We’ve already covered that above.
That’s the minimum amount of power you need from solar panels.
If a refrigerator uses 1.8kWh daily, we need solar panels that produce at least 1,800W.
Because solar panels don't always produce the rated output (that is, a 200W module doesn't always produce 200W), add a margin to account for this.
On average, solar panels produce 70-80% of the indicated output.
To be sure we’ll get 1,800W from our solar panels, we add a 30% margin to get 2,340W.
We need solar panels that give us at least 2,340 Watts or about 2.3kW of power in a day.
Next, we need to calculate required solar output per hour. That will help us choose the size of solar panels to get.
To do this, we divide the total daily output by the number of peak sun hours in our location. These are the hours when sun intensity is highest, and thus solar output is also highest.
Number of peak sun hours varies by region, but most places get at least 5 on most days. Use this tool from the National Renewable Energy Laboratory to get the peak sun hours for your specific address.
To calculate required hourly solar output, we divide 2,340W by 5 hours to get 468W. This is the size of the solar panels that we need.
Solar panels have gotten much cheaper, so it doesn't hurt your pocket to get more than you need. We can connect three 200W solar panels to get 600W, plenty enough to supply the 468W we need.
Each day, our three solar panels will produce on average 3kWh of power (600W x 5 peak sun hours). That’s plenty to cover the 2.3kWh we need for our refrigerator.
What Size Solar Battery Do I Need To Run A Refrigerator?
You need a battery that stores enough power to run your refrigerator for 1-5 days, depending on the days of autonomy you want (more on that shortly).
The first step is to calculate how much power the refrigerator consumes in a day. Check above for those calculations.
Going with our example, our refrigerator needs 1.8kWh each day or 1800Wh.
That’s the minimum amount of solar battery capacity we need. But, as we’ve already mentioned, solar batteries don't discharge to 100%.
So we can’t just get a 1.8kWh battery. It won’t be enough.
Lithium batteries generally discharge to 80%. Add a 20% margin to the amount of power your fridge uses daily.
In our case, we need a capacity of 2.7kWh to get 1.8kWh of energy each day.
If we were to get lead acid batteries, we’ll need double the amount of power the fridge needs. That’s because lead acid batteries discharge to 50%.
So to get 1.8kWh each day, you need a battery capacity of 3.6kWh.
Now, let’s talk about days of autonomy.
If you live in an area that’s sunny most of the year, storing just one day’s worth of power might be enough since you can easily recharge the batteries the next day.
But for most homes, it’s a good idea to store enough solar power for 3-5 days of use just in case there’s bad weather and you cannot generate solar power. These are called days of autonomy.
For most people, 3 days of autonomy are adequate.
Take the amount of battery capacity you need each day and multiply it by 3 (or the days of autonomy you want).
In our example, we’ll need a total capacity of 8.1kWh with lithium batteries (2.7*3) or 10.8kWh with lead acid batteries (3.6*3) to run our refrigerator for three days even on cloudy days.
Because batteries are often sized in ampere-hour (Ah) instead of Wh, let’s convert these numbers to Ah to make it easier to find the battery we need.
To do this, we divide Wh by the battery voltage to get the total Ah we need for our battery bank.
8100Wh/12V = 675Ah lithium battery bank
10800Wh/12V = 900Ah lead acid battery bank
If you are setting up a 24V solar system, divide by 24V above instead of 12V.
Four 200Ah 12V lithium batteries (800Ah total) or three 300Ah lead acid batteries (900Ah total), should be enough to power our refrigerator for up to 3 days.
Plug in your own numbers to get the total battery capacity you need for your particular situation.
If, for instance, you want to power a mini fridge in your RV, you won’t need the same amount of capacity as you would for a large kitchen refrigerator.
Sizing Other Solar Components
You’ll need two other major components to set up a solar system for your refrigerator: a charge controller and an AC inverter.
Charge controllers are rated in amps. Divide your solar panel output by the voltage of your battery bank to figure out the charge controller size you need.
If you have three solar panels producing a total of 600W and you have a 12V battery bank, 600W/12V gives you the amperage the charge controller needs to handle.
In this case, it’s 50 amps. So a 60A solar charge controller is ideal (always oversize your charge controller to be safe).
As for the inverter, we look at how much power the refrigerator pulls from the battery.
If your fridge has a rated input of 300W, you need an inverter that can provide this amount of power continuously.
If you plan to power more than one appliance at the same time, make sure the inverter can handle the combined draw of all appliances.
Frequently Asked Questions
Will a 100W solar panel run a fridge?
A 100W solar panel delivers between 300Wh and 600Wh of power each day depending on solar intensity.
That’s enough to run a small mini fridge for an RV or camping.
Will a 400W solar panel run a refrigerator?
A 400W solar panel produces between 1.2kWh and 2.4kWh each day. That’s enough to power a regular kitchen refrigerator for a few hours or a full day.
How long will a 12 volt battery run a refrigerator?
It depends on how much power the refrigerator uses. To calculate run time, divide battery capacity (in Wh) by the average wattage of your fridge.
To get average wattage, divide the power rating of the fridge by 3. E.g. A 150W refrigerator has an average wattage of 50W.
What do I need to run a fridge on solar?
An easy way to run a fridge on solar is by plugging it into a solar generator, also called a portable power station.
Then get solar panels to recharge the solar generator.
Alternatively, set up a solar system with solar panels, a solar charge controller, a battery bank, and an inverter. Wire all these together (along with fuses) to deliver solar power to your refrigerator.
Can you run a fridge straight off a solar panel?
Yes, you can run a 12V refrigerator directly off a solar panel without batteries. You’ll need a charge controller that can support direct DC loads.
But this is not ideal since solar output fluctuates and is only available when it’s sunny.
A better set up is to connect a solar panel to a battery and then run your fridge from the battery.