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Refrigerators and freezers need a consistent power source to keep food fresh, so solar power might not seem appropriate at first. But with the right PV system setup, you can run any type of freezer without problems.
2 x 300 watt solar panels can run a 20 cubic foot freezer. To keep the freezer running for 24 hours you need two 100ah AGM batteries.
Freezer Solar Panel Requirements
To be clear, this guide is for freezers only, and does not include refrigerators with freezers. We have a separate guide if you want to run a refrigerator on solar power. While there are all kinds of freezers, it is possible to use the following guidelines and determine how much solar power you will need
The formula is: find the freezer power consumption in watts and add 20%. The result is the minimum solar panel size you should use. The following chart shows the most common freezer sizes, their power consumption and the minimum solar panels required.
|Recommended Solar Panel Size
|1 to 3 cu ft.
|20W – 100W
|100W – 120W
|5 to 9 cu ft.
|50W – 120W
|12 to 18 cu ft.
|200W – 440W
|18 to 22 cu ft.
|350W – 500W
Solar panel power output should be rounded off to the nearest size available. If a 9 cu. ft. freezer requires 144 watts of solar power, get a 150W PV module. We recommend the Newpowa 160W solar panel as it is made of high quality monocrystalline and can be used in homes, RVs and boats.
If your 15 cu. ft. freezer needs 528 watts, two 275W or 300W solar panels will do. A good choice would be the Huajin 300W flexible solar panel as it has a high efficiency rating and works in different environments.
As you may have noticed the power consumption varies quite a bit. That is because freezers come in a wide range of sizes, shapes and designs. Some models are also more energy efficient than others.
These requirements and calculations are for regular use of freezers during the summer. During other seasons there is less sunlight so compensations have to be made. But since most people use freezers during summer the computations are valid.
Freezer power consumption is affected by several factors, so under certain conditions a freezer may consume power than what you might expect. This is particularly true if the freezer is full.
How Long Can Solar Panels Run a Freezer?
The runtime for solar powered freezers depends on its power consumption and how much power the solar panel can produce. While there are other factors to consider we can provide some useful examples here.
The majority of portable freezers are from 1 to 5 cubic feet, and are typically used for camping. Most consume less than 100 watts so a 100 watt solar panel can run a portable freezer for 5 to 6 hours a day.
If you have a larger freezer, the same rule applies. Whether it is a 9 cu. ft. 150W model or a 350W 15 cu. ft. freezer, use the same formula given, add 20% to get the solar panel size you need.
Should you get a larger solar panel? It will cost more and can be difficult to carry if you are camping. But a larger solar panel or array (panels connected together) will provide more power.
The power consumption is not an issue, it is the number of sun hours available. If the solar panel rating is equal (or preferably 20% higher) than the freezer wattage, the panel can run it.
Suppose you have a 350W freezer and a 600W solar array. Not only will the system run the freezer, but you would have enough watts left to power other devices.
The only limitation is the sun. If there are 5 sun hours available the panel will power the freezer for 5 hours. But when the sun sets, solar panels can no longer run. So if you want to keep a freezer operational past sunset, another power source is required.
Do You Need a Battery to Run Freezers on Solar Power?
Almost everyone who runs freezers on solar panels use a battery, because without it you will not be able to use the freezer when the sun goes down.
A 50ah battery can run a 3 cu. ft. freezer for about 3 hours. To run a 5 cu. ft. freezer for 24 hours, a 150 watt solar panel and a 400ah battery are required. You can use one 400ah battery or several smaller batteries like five 80ah for instance.
In this scenario, our 5 cu. ft. freezer uses 120 watts an hour.
120 watts x 24 = 2880 watts
A 150 watt solar panel can produce 750 watts in an hour.
That means you need another 2130 watts, which a 400ah 12V battery bank can supply. 400ah is actually 4800 watts, but only half – 2400 watts – is usable per charge on lead acid batteries.
By combining 2400 watts plus the 750 watts from the solar panel, we have 3150 watts, more than enough to power the freezer for an entire day.
This solar panel and battery combo produces more power than what our 5 cu. ft. needs. But in many instances, the panel and battery may not reach 3150 watts, which is why we have added a safety margin.
Solar panel cells are sensitive to shading, and even a few leaves blocking the panel can slow production significantly. A cloud that suddenly blocks the sun has the same effect. So make sure the sky is clear when you set up a solar panel.
Batteries provide a steady stream of power, which is why they are ideal for freezers and other appliances. However it is dependent on the solar panel to supply the power. If there is limited current going into the cells, the battery will not be able to power the freezer. One way to ensure optimum power is to make sure the solar panel and battery are at the right distance from each other. And even if you have the solar panel and battery, you still need a couple of things to get the freezer going, an inverter and a charge controller.
Inverter and Charge Controller
Portable freezers may be connected directly to a solar panel, but larger models often function like refrigerators. So you need an inverter to run them. Solar power – which is DC – will pass into the inverter and get turned into AC so it is compatible with the freezer.
A charge controller is set between the solar panel and battery, and it protects the battery from overcharging and overloading. The controller also shuts off the battery once the discharge level is reached and ensures the system charges at the proper voltage.
A freezer on a 12V solar panel system requires a 20A charge controller. Technically a 12A controller should be sufficient, but due to numerous factors the voltage and amps can go up to 17, so a 20A controller is best.
If your freezer runs on AC, an inverter is needed to run it on solar power. The rule of thumb is the inverter capacity must be 25% larger than the load. Using this guide, a 150W 9 cu. ft. freezer needs a 200W inverter.
We have a detailed guide for inverter freezers so you should check it out if you want to install a full PV system for your freezer. The point is the solar panel, battery and inverter have to match to keep any appliance running smoothly.
Which Type of Freezer is Best For Solar Panels?
Our goal of course, is to use the most energy efficient freezer possible. However there are other factors that should be considered because some freezers are designed for particular tasks. See which one below best fits your situation.
As the name suggests, these are lightweight freezers designed for picnics, camping, tailgating and generally any outdoor activity. They often use less than 100 watts so a portable solar panel will be enough.
Some portable freezers run on AC, but others use DC power. So check the specs if you will need an inverter. For keeping foods and drinks cold on the go, a portable freezer is often the most sensible option.
Upright freezers are available in various sizes ranging from portable to over 18 cubic feet. They consume more power than chest freezers, but its advantage are its organizational shelves.
You can arrange the contents of an upright freezer easily, so no need to dig through the whole thing if you are looking for something. While you will not save as much power compared to a chest freezer, more energy efficient upright freezers are being developed.
Chest or deep freezers are shaped like a box and the most popular type available. They are bulky and don’t have shelves, but it uses less solar power than upright freezers. Plus they are more affordable.
Chest freezers also come in a wide range of sizes. Some take up as much as 40 cubic feet, but others are only 2.1 cubic feet. This means you have a lot of choices when it comes to deciding which one best fits with your PV solar panel.
The popularity of PV systems have led to the development of solar powered freezers. While they are still not yet commonplace, majority of freezers are now energy efficient to the point it is easier to run them on a solar power system.
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.