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400W solar panels are becoming more and more popular owing to their capacity and affordability. For off grid homes and applications, they make a lot of sense and are practical to use. One question that often comes up is whether a 400W solar panel can power a refrigerator. That is what this article will answer in detailed and simple terms.
A 400W solar panel can run a 12V DC fridge for 5-6 hours a day. If you connect a 100ah battery to the solar panel, you can keep the refrigerator going for 12-16 hours.
How Long Can a 400W Solar Panel Run a 12V Fridge?
To answer that question we need to know two things: how much power the fridge consumes and how long it will run per day.
The formula is:
Refrigerator daily power consumption (ah) x voltage = solar panel watts required
Number of sun hours = refrigerator runtime
Refrigerator power consumption is measured in amp hours (ah), so we have to convert this into watts to find out how much solar power is needed.
To convert amp hours into watts, multiply the amps by its voltage. A 12V 30ah fridge uses 360 watts a day:
30 x 12 = 360
A 12V solar panel like the Renogy 100W has an amp output of 8.3 amps an hour. If you connect four of these in parallel for 400W, you get up to 33 amps. That is more than enough for a 60W 12V fridge that draws 5 amps an hour on average.
This table shows the average power consumption of various 12V refrigerators. These appliances have an on/off cycle so they are typically on for 5-6 hours a day.
|Refrigerator Capacity in Liters||Ave. Power Usage in Winter||Ave. Power Usage in Mild Weather||Ave. Power Usage in Summer||Ave. Solar Panel Power Needed Daily|
|70L and higher||45ah||65ah||90ah||540-1090W|
Since a 12v fridge is on for 5-6 hours a day, the fridge uses 25-30 amps daily on average. As shown in the calculations above, that is 360 watts a day.
If your solar panel can produce up to 400 watts an hour, it should have no problems running a fridge that requires 360 watts a day. However, there are several reasons why it is not practical to run a fridge on solar panels alone, and why a battery is needed.
Why Your 400W Solar Panel Needs a Battery
The problems with running a fridge on solar panels alone is that it is limited to working in daylight. Second, it is dependent on clear weather. By using a battery with your solar panel, you can store extra power to run any appliance without sunlight.
Solar Panels Need Sunlight. That might be stating the obvious, but this affects how long you can run a fridge. Take the following example.
Suppose you have 2 x 200W solar panels for a total of 400W. Its amp output will be anywhere from 8.3 (series connection) to 33.2 amps (parallel). Either way it will be more than enough to handle a 12V fridge that only needs 5 amps an hour.
The Weather Factor. The problem is you are limited by the number of sun hours available per day. If you only get 5 hours of sun per day, that is how long you can run the fridge. At the end of the day, without any sun, your solar panel cannot produce electricity.
The other issue is the output depends on the weather. On a clear sky, a 400W solar panel will produce 400 watts or close to it. But clouds, a sudden storm, debris shading one of the panels etc. will cause its output to drop.
A refrigerator needs a reliable, consistent power source to keep food fresh. This is where a deep cycle battery is going to be necessary. With the right battery and solar panel you can keep the fridge running even at night.
How Many Batteries to Run a 12V Fridge and 400W Solar Panel?
By using a 100ah battery with a 400W solar panel, you can keep a 12V refrigerator running for up to 16 hours or more.
Let us use a 30L 12V battery as an example. If this fridge uses 5 amps an hour and there are 5 hours of sunlight per day, your solar panel can run it for 5 hours, for example from 10:00 AM until 3:00 PM.
If you have a 100ah battery with a 50% depth discharge, you can run the fridge for another 10 hours before capacity drops to 50ah and it needs to be recharged.
So at 3:00 PM you can let the battery take over for another ten hours. If you have a lithium battery you can run it up to 85-100% capacity. A good choice would be the Ampere Time LiFePO4 100ah as it is optimized for refrigerators and other appliances.
The larger the battery the longer it can run your fridge. A 200ah lithium battery offers twice the capacity and running time.
Another thing you can do is run the fridge entirely on the battery. For instance, if your 12V fridge only uses 30ah a day, a 100ah battery will be enough. Allow the battery to power the fridge and use the solar panel to recharge it.
Here is another example. You are out camping for 3 days and want to use the fridge for 6 hours a day. How many batteries will you need?
Assume the fridge consumes 35ah a day. If there are four hours of sun available, your solar panel can provide 20 amps. But let us be conservative and assume the day is overcast and you can only get 15 about amps. That means you need another 20 amps to get to 35.
With a 100ah battery you can run a 12V fridge for 3 days. 15 amps is provided by your solar panel so you only need 20ah per day from the battery.
That should leave you with about 80ah battery power left at the end of each day. That is enough to run the fridge again tomorrow, then as the sun comes up you can recharge it with the solar panel.
With a large battery you do not even need a 400 watt solar panel. Even a few 170w solar panels will be enough. All of these numbers assume that your solar panel and battery will only run the fridge. If you are going to load other appliances, you will need a larger battery bank and more panels.
What Factors Determine Refrigerator Power Consumption?
If you looked at the table earlier, you will see that it has low, average and high power consumption levels. There are many factors that affect the power wattage of a refrigerator, and it is something you always have to consider.
Temperature. The hotter it is, the longer the refrigerator compressor has to work to keep the interior temperature cool. The colder it is, the less work for the compressor and the lower the power consumption. This makes a huge difference in terms of power usage.
Insulation. A quality fridge has excellent insulation. Its doors latch tightly to keep the coldness in. These are two important features you have to look into when buying a 12V fridge.
Usage. When you open the fridge door, the thermostat activates to keep the temperature low. Of course this will require more power and increases its consumption. That is why you should limit the number of times you open the door, especially during summer.
Quality. Some refrigerators are more energy efficient than others. If you are going to get one to work with a solar panel and battery, make sure it is an energy efficient model.