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12V refrigerators and freezers are a nice alternative to a standard fridge. For camping or living in an RV, it is a practical and cost effective alternative. But how many solar panels will you need, and what sizes?
A 12V fridge draws 1 to 5 amps an hour. A 100W solar panel is enough to run it, but a 100ah battery is needed to keep the fridge going for 24 hours or longer.
How to Calculate 12V Fridge Solar Power Requirements
A typical 12V fridge uses amps to measure power consumption. Since solar panel output is in watts, you have to do a conversion.
Amps x volts = watts
If you have a 12V fridge that draws 2 amps an hour and you need to run it for 5 hours:
12 x 2 = 24
That is 24 watts an hour.
24 x 5 = 120 watts
A 12V fridge that draws 2 amps an hour requires at least 30 watts of solar power. The nearest common solar panel size is a 50 watt solar panel.
A 50 watt solar panel can produce up to 250 watts with 5 hours of sun. This is enough to run the fridge. If that is all you need, the Newpowa 50W PV Module is sufficient. You can run the fridge off the panel directly if it is DC powered.
You can figure out the solar power requirement of any 12V fridge with this formula. All you need to know is its hourly amp draw and multiply it by 12.
The result is the minimum solar panel output required. Because solar panel production depends on sun availability and intensity, having reserve capacity is ideal. If the fridge uses 35 watts, get a 50W solar panel. If the fridge requires 55 watts, get a 75 or even a 100W solar panel.
You might be able to get away with the minimum solar panel requirement during the summer. But if you camp during spring, fall or winter, a large PV module is better.
12V Chest Freezer Solar Panel Size Guide
12V refrigerators and freezers come in all sizes and measurements. The following table lists the most commonly used sizes today. Always check your product manual for more specific details.
|Capacity||Amp Draw Per 24 Hours||Watts Drawn Per 24 Hours||Suggested Solar Panel Watt Size|
|30-50L / 31-52 quarts||35ah||420||500|
|50-70L / 52-52-73 quarts||45ah||540||600|
|80L / 83 quarts||65ah||780||800|
The power draws given here are daily 24 hour averages from common models. Power consumption might be lower or get higher depending on usage, how full the fridge is, settings, etc.
The recommended solar panel sizes are only for these power usage ranges. For instance, some 80L 12V freezers consume 85ah or more than 1000 watts. An 800W solar panel will be insufficient so keep that in mind.
Always check the specs for the fridge. But also consider how long you will use it and its capacity. Just like a kitchen refrigerator, the fuller the fridge, the more power it will consume to keep the contents cool.
How Long Will a 12V Fridge Run on Solar Panels?
It depends on how much power the fridge uses, the solar panel output and how many hours of sun are available.
A 50W solar panel can run a 12V 3 amp freezer as long as there is enough sunlight to generate at least 36 watts an hour.
Example, you have a 12V freezer that draws 2 amps an hour. That is equal to 24 watts.
You have a 50 watt solar panel and there are 5 hours of sunlight. On paper a 50W solar panel can produce up to 50 watts an hour, but cloud covering, shading, sun location in the sky etc. means the output will probably be 40-45 watts.
Even so that is almost double what the fridge needs. As long as there is sunlight, the solar panel will keep the fridge going.
The more sun hours available, the longer the fridge can operate on solar panel power. Before you go camping, keep the following in mind:
- Check how many watts the fridge uses per hour. Remember, amps x volts = watts.
- Calculate how many hours you will use it
- Determine how many hours of sun are available
Example: you have a 40 liter 12V fridge that consumes 2 amps an hour.
2 amps is 24 watts, which is 120 watts for a 5 hour runtime. It takes 120 watts of solar power to keep the fridge running.
A 50 watt solar panel should be enough especially during summer. A 12V freezer uses up to 5 amps so you need more solar power. Consider a 100 watt solar panel or better yet, add a battery bank.
How Many Batteries Does a 12V Fridge Need?
Actually you don’t really need a battery to power a 12V fridge. But it is more practical to do so as we will show. The number of batteries required depends on how many hours you want to run the fridge.
You have a 40 liter fridge and you want to run it for 3 days or 72 hours. You have two options:
- Use the solar panel as a charger and run the fridge from the battery
- Run the fridge from the solar panel then switch to battery mode when the sun sets
The first option requires more battery power but is more practical. You don’t have to do any switching, plus the power supply source will not fluctuate regardless of the weather.
To run a fridge on battery for 72 hours, calculate its amp consumption. Assuming it is 2 amps per hour, that would be 144 amps for three days.
A 150 ah battery can run a 2ah 12V fridge for 72 hours. If you don’t want to empty the battery, get a 300ah or two 150ah batteries. The NPP 155ah AGM Battery is going to be enough for most, or you can get two of these if you don’t want to fully discharge the batteries.
To run the fridge on solar panels and battery, calculate how many sun hours are available.
Using the same fridge as above, you need 144 amps for 72 hours. 144 amps is 1728 watts.
The fridge pulls 48 amps a day or 576 watts. A 120-150ah battery paired with a 100 watt solar panel should be enough to operate the fridge for 72 hours.
Benefits of Running a 12V Fridge on Batteries
With a battery, you can run the fridge for 24 hours or longer. Even when the sun goes down there is power available.
Power supply is constant and reliable. Solar panel power ebbs and flows depending on the intensity of the sun. When the sun sets, there is no more power.
Another benefit of having a battery is you can store excess solar power that would otherwise be wasted.
Suppose you have a 60 liter freezer that pulls 5 amps or 60 watts an hour. You have a 100 watt solar panel that generates 90 watts an hour.
The 60 watts goes to power the fridge, but what about the other 30 watts? If you don’t use it, the power goes to waste. If the solar panel runs for 5 hours, that is 150 watts wasted.
With a battery, you can store the extra power for later use. Using the same example, you could end up with 150 watts of power available, enough to run the fridge for about 2 hours even without sunlight. So it makes sense to use a battery.
Tips For Using Solar Power on 12V Fridge and Freezers
- If the fridge runs on DC power you don’t need to use an inverter. You can run it straight from the solar panel. But if it uses AC power, you need a portable inverter to convert DC to AC.
- Decide what type of 12V fridge you want. Will it be used as a fridge or have a freezer function? Freezers use more power.
- Are other power sources available? If yes, you can opt for a smaller solar panel and battery. If not, use the solar panel and battery sizes recommended here.
- How many people will be going with you? More people means a bigger fridge and higher power draws.
- How long will you use the fridge? A few hours, days or weeks?
- What is your budget?
- How much capacity do you need? A larger fridge can store more food and drinks, but the power consumption will be higher.
There are many types of 12V refrigerators and freezers available. They come in different specs so there should be one that fits you. As long as you plan ahead, running a 12V fridge on solar power is going to be smooth sailing. .
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.