how much solar power do i need to run a refrigerator

How Much Solar Power Do I Need to Run A Refrigerator?

Thinking about switching to solar just to power your fridge? Now would be a good time to finally make the leap since solar power can do much more than that. While some people only use solar energy to power their lighting systems and other light appliances, it has the potential to power your refrigerator and help you save hundreds of dollars in a year. However, a lot has to be taken into consideration.

First off, the answer behind how much solar power you need to run a refrigerator lies in the number of solar panels you need. A simple answer would be to say that about three to four solar panels could do the job, but you wouldn't know which solar panel is best for your case. In addition, you'd also need to know how much power your refrigerator consumes since different refrigerators consume different amounts of energy.

If all that sounds interesting, but you don't know where to start, then you've come to the right place. In this article, we explain why it's important to understand your refrigerator's energy requirements before outlining the kind of equipment you'll need for the setup and why. Additionally, we'll also discuss a few important tips that can help you get the most from your solar power system.

Most electrical appliances we have at home consume different amounts of electrical energy. Whereas the power consumption of your smartphone will be low, your refrigerator may not always go easy on your electricity bill. This is especially true if your refrigerator has lots of functionalities. 

To know how much solar power you need to run your refrigerator, you would first need to know how much energy your refrigerator consumes, and there are several ways of finding this out. 

First, you can find this information on the energy rating label. Most refrigerator manufacturers usually place a sticker containing the energy rating on the door. The amount of power the refrigerator consumes is usually indicated in KWh per year and can range anywhere from 200KWh per year to over 600KWh per year. 

Of course, more means that the fridge consumes more power in a year, and this means you will have to part with a little more cash when setting up a solar power system specifically for your fridge.

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If your refrigerator doesn't have the energy rating sticker, you can still estimate the value by first finding out its power rating. It is usually measured in watts and you can find this information next to where your fridge's serial number and model are indicated. 

This can also be estimated by multiplying the voltage by the amps the fridge needs. Typical values can range from 100W – 400W or more. You can then proceed to convert this to KWh depending on how long you use the fridge.

The KWh value will be important in determining how much power your refrigerator alone consumes. With this, it will then be easy to size the solar power system and know exactly how many solar panels you need and how big of a battery will be needed to power your refrigerator.

If you would want to power other appliances other than your fridge, then you should include them in your total energy consumption too.

What You Will Need for The Solar Power System

Now that you have an idea of how much power your refrigerator consumes, it becomes easy to pick the other equipment that will be vital in the solar power system. Ideally, you will need the following:

  • Battery
  • Inverter
  • Charge controller/regulator
  • Solar panels

Batteries and solar panels are actually the heart of a solar power system. Their individual efficiencies will greatly influence the overall efficiency of the entire system. The batteries, however, are what will store energy and enable you to use power when there's no sunlight e.g. at night. Inverters and charge controllers, on the other hand, ensure efficient transmission of power within the system.

Battery

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Typical solar batteries deliver 12V of electrical energy, but their ampere hours (Ah) differ from one another. Ampere hours simply describe the battery's capacity by indicating how many amps a home appliance can draw from a battery and for how long.

As an example, a battery that's rated 240Ah means that it can theoretically provide 10 amp for 24 hours. However, it is worth noting that batteries are rated using a 20-hour cycle. This means that this same 240Ah battery can provide 12 amps per hour for 20 hours.

Calculate Appropriate Battery Size

With that in mind, you should then proceed to calculate how many watts are needed by your refrigerator in case you need it to run for the whole day. The main reason we are calculating it on a day basis is because you can easily adjust how many hours you'd need to run your fridge on solar power.

If the running watt hours of your refrigerator is say 110W/h, you can get the total watts it requires in a day by multiplying this value to 24.

Daily Total Watts Your Fridge Uses: 110W/h X 24h = 2640W

Next, we now need to know the amperage required. To do that, we simply divide the daily total watts by the voltage of the solar battery. 

Total Amps Needed: 2640W / 12V = 220A

Ideally, to power our 110W/h fridge, a 12V battery rated at 250Ah would work. However, since we never want the batteries to go below 50% depth of charge, you should multiply this value by two.

Required Battery Size: 220A X 2 = 440A

Thus, in this case, a 500Ah battery would be perfect since it can deliver over 220Ah without going below 50%. Here too, you should note that the higher the amp-hours, the more expensive the battery will be.

However, depending on how you install the solar power system, you can choose to power your refrigerator with electricity from the grid during certain hours and then use solar power for the remaining hours.

If, for instance we chose to use the solar power for only 12 hours, then a 250Ah battery would be just fine since it would only use 110Ah in 12 hours before going below the 50% mark. Doing this will lower both your electricity bill and the initial cost of setting up a solar power system.

Battery Types

One other thing to note about solar batteries is that they come in several types. You can choose from either flooded lead acid batteries, sealed lead acid batteries, or lithium batteries. 

Flooded lead acid batteries are cheaper, but they also require some maintenance and have average lifespans of 5-7 years. On the other hand, lithium batteries cost more but are usually more efficient and have impressive lifespans of more than 10 years.

Inverter

Batteries may be the heart of a solar power system, but without getting a proper inverter, the whole system could still be inefficient. As earlier mentioned, inverters convert DC power from the battery to AC power for your refrigerator. This conversion will always result in a loss of electrical power regardless of the inverter you're using. As such, choosing an inverter with high efficiency is the way to go, but there are a few things to consider here as well.

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Inverter Sizing

Your inverter's operating voltage should be the same as that of your battery. This will also apply when getting solar panels as they too need to have the same voltage as your battery and inverter. Sizing an inverter will also require you to know a little bit about the continuous running watts and the surge watts rating.

Continuous Watts vs. Surge Watts

If you intend to use your solar power system to power your refrigerator alone, then you really needn't worry about the surge watts rating or continuous watts rating of your inverter. This is because you can simply get one that has a rating which is slightly higher than your fridge's energy requirement. However, if you plan to power multiple appliances, then the two become very important.

Continuous watts rating indicates how many watts your inverter can support. This means that a 2000-watt inverter will only supply 2KW. Surge watts, on the other hand, indicates how many watts the inverter can supply for a short duration. Refrigerators usually have surge watts of up to 1.5X. As such, you should ensure that your inverter can handle at least 1.5 times the wattage of your refrigerator.

Wire Length

The length of wire you use between your solar panels and your battery is also crucial because longer wires tend to result in more voltage drops. You should use shorter wires if you are only dealing with high voltages and low currents. If you still have to use longer wires, then the wires also need to be thick so that they can transmit power efficiently.

Is Inverter Stacking Good for Refrigerators?

While some people opt to stack inverters so that they can get more power, you'll hardly need this since a single efficient inverter will be enough to power your refrigerator. Regardless, stacking is still a great way to expand your solar panel power in the future since you would only need to buy more solar panels and add an extra battery to your bank in case your current battery bank is not as powerful.

Charge Controllers

Use of a charge controller will also be inevitable if you intend to power your refrigerator with solar power. While solar power systems could sometimes work without charge controllers, this only applies if you are using solar panels that deliver 5W or less. This won't be the case with refrigerators since they consume a lot more power.

Choosing the Right Charge Controller

Nevertheless, sizing a charge controller is super easy since it only requires you to be keen about two things:

  • Voltage
  • Current capacity

Just like with inverters and batteries, the voltage of the charge controller you choose should match that of all the other devices you have in your solar power system. Charge controllers are also rated at 12V, 24V, and 48V which means you will always have a charge controller that is just right for you.

One great thing about charge controllers though, is that you can get some models with voltage auto-detect feature. This will allow you to use it in almost any kind of solar power system without necessarily having to worry about the voltage. In addition, such charge controllers can also come in handy in case you want to upgrade your solar power system in future.

Your charge controller should be able to handle the maximum output current from your solar panel array. Usually, a solar panel's maximum current (short circuit current) is what you need to keep an eye on. It is indicated as LSC in your panel's spec sheet, and it is good practice to choose a charge controller that can accommodate up to 1.25 times the value of your panel's LSC.

This is because solar panels could easily produce an extra percentage of power on sunny days. If the charge controller you installed has a lower amp rating, then it can get damaged when the current from the solar panels is higher than what the charge controller can handle.

Ideally, if you have a 12V solar panel that gives anywhere from 5W to 45W, then a 4-amp charge controller would suffice. However, if you have a slightly bigger system that relies on a 24V solar panel that delivers up to 160W, then you may need a charge controller that can handle more than 10A.

For fridges though, chances are that you might be content with a 4-amp or even 7-amp charge controller because they can do the job without any fuss.

Solar Panels

Without solar panels, there wouldn't be any solar power for your refrigerator, and this is why they too are crucial. Earlier on, we suggested that about four solar panels could easily power your refrigerator. But this isn't always the case, especially when the discussion on batteries, inverters, and charge controllers shed light on the importance of sizing. Sometimes, even a single solar panel can still power an entire refrigerator comfortably.

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There are, however, a number of things to consider when picking solar panels as well. Some of them include:

  • Solar panel quality
  • Solar panel size
  • Hours of sunlight

Solar Panel Quality

Your refrigerator alone probably wouldn't need the best of the best when it comes to the actual solar panel, but getting a quality solar panel would work more in your favor. A good quality solar panel is one that is highly energy efficient, has a low temperature coefficient, and uses efficient solar cells.

In terms of energy efficiency, a good solar panel should be able to convert most of the light it receives into electrical energy. Such efficient solar panels come in handy during days with poor sunlight since they'll still be able to trap as much sunlight and convert it to electricity.

Good quality solar panels also experience less impact from heat. Since solar panels are meant to stay in the sun all day, they can at times overheat and this can accelerate their ageing process. However, a solar panel with a low temperature coefficient means that temperatures won't impact performance severely unless they go over a certain threshold.

Also worth noting about solar panel quality is that the type of solar cell used can make a big difference. There are usually three main types of solar cells:

  • Monocrystalline – Highly efficient and has impressive heat tolerance
  • Polycrystalline – Average efficiency and a great choice for residential homes
  • Amorphous – Least efficient

Solar panels that use polycrystalline solar cells are a great choice for most cases and they can comfortably power your refrigerator. However, if you do have some extra cash, then it wouldn't hurt to go for the more durable monocrystalline solar panels.

Solar Panel Size

Physical size of a solar panel is important, but you should first consider the wattage first as this is what will power your entire system. Based on your refrigerator's requirements which we had earlier looked at, you can proceed to pick a solar panel that will meet your needs first and in an efficient manner. Bear in mind that the number of watts indicated on a solar panel directly relates to the watt hours it can produce. As such, a 150W solar panel can generate 150Wh.

Hours of Sunlight

Apart from the size of a solar panel, the duration of sunlight in your area can also affect the number of solar panels you need to install. If the quality of sunlight in your locality is poor, you might need to install more panels to get the minimum wattage required to power your refrigerator. As such, you should look up the daily peak sunlight hours for your region. This will allow you to now calculate the number of solar panels you need. You can do that by multiplying your refrigerator's hourly energy requirement by the peak sunlight hours then dividing that by a panel's wattage

No of Solar Panels = Average Hourly Energy Requirement X Peak Sunlight Hours / Solar Panel Wattage

How to Get the Most Out of Your Solar Power Installation

Most people use their solar power systems to operate a few household appliances other than refrigerators. Regardless of the case, there are always more ways of getting the most from your solar power system in terms of efficiency, and battery lifespan. Below are some of the things you can do to get started:

Take note of power-hungry appliances

You can reduce your energy requirements by considering certain appliances that still consume power in standby mode. Modern TVs, gaming consoles, and even surround sound systems consume electricity even when in standby mode. This means that even though they're off, they can still draw power from your solar power system.

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Of course, sizing is supposed to take care of the energy requirements of all devices in your home, but occasionally keeping some of these devices off when they are not in use can conserve a lot of energy. Devices that have a continuous display of some sort are usually big culprits too. Simply unplug them so that they won't consume any power in idle mode.

You can end up saving up to 10% of energy used in your home in a year. This will not only be good for your battery, but also for the other devices you used in your solar power system. In the end, you can expect your solar power system to serve you for a long duration.

Other than saving energy, you will also save on the initial cost required for setting up the solar system since your average energy use will go down when you completely switch off some of the appliances that you have.

Be wary of your refrigerator's power usage fluctuations

If all you wanted to power was your fridge, then you should know that the power it uses can vary depending on what you do to the refrigerator itself. Normally, sizing usually covers your fridge's operating power and surge power whenever it is connected to power. 

However, certain practices can dramatically increase the power usage of your fridge. Storing hot foods in your fridge, for instance, will make it overwork so that it can maintain temperatures inside the fridge at the temperature level you set. This will then cause it to draw much more energy than was initially planned for.

If sizing was not done correctly, such a solar power installation may end up being inefficient as it won't meet your needs properly. This can be worse if you also use the same solar power setup for other devices as well because your fridge will now consume more power that was allocated for the other devices.

While sizing can indeed solve such a problem, the logical solution would be to simply use your fridge the right way. That means you shouldn't leave the doors open and you should also avoid placing hot foods inside the fridge.

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Take care of your battery

In most solar systems, batteries are usually the most crucial because they supply power to your appliances even when there's no sunlight. We also briefly looked at three types of batteries that you can use for your solar power installation and realized that some require maintenance while others don't. Of course, batteries that require more maintenance will need you to keep a closer eye on them than those that don't. But that is not the only way of increasing your battery's lifespan.

If you have several batteries in your battery bank, try and reduce them. Having too many batteries at the bank increases resistance and can ultimately result in unequal charging. That is why it is preferable to have a single battery whenever possible. On the same note, ensure that you don't leave your batteries uncharged for a long time.

You should also ensure that you keep your battery or battery bank in a cool place and away from high temperatures. When solar batteries are exposed to high temperatures, their cyclic life is reduced. As such, you won't enjoy the full efficiency of your solar power system and the lifespan of your batteries will be significantly reduced.

Clean your solar panels occasionally

In as much as you can simply leave your solar panels on the roof and forget about them, dirt and other materials are bound to settle on top of the panels. The result? Parts of the solar panel will not effectively generate the power they are supposed to produce, and this will lead to slower charging of the battery. 

It is thus a good idea to keep your solar panels clean. There's no right or wrong period for which you can do this, but if you have lots of trees around which drop their leaves on your roof, then you might need to clean more often. You should also ensure that your solar panels are away from any shade as this will have an even bigger impact on the effective power produced.

In practice, it's not always necessary to clean your solar panels if they are still delivering good enough performance. In fact, occasional rainfalls will do the cleaning for you. But you can also opt to install monitoring systems that will allow you to document the daily performance of your solar panel. Be sure to conduct most of the tests when there is no cloud cover and when there is heavy cloud cover as well and use these values as the maximum and minimum your solar panels should generate.

Conclusion

In summary, there is no one right answer as to how many solar panels would be required to power your refrigerator because there are a number of factors involved. The easiest way would be to multiply your fridge's hourly energy requirement by the peak sunlight hours then divide the value by a panel's wattage. However, you would still need to know one or two things about the type of solar panel that would work best for you. 

In addition, since you'll require other equipment like charge controllers, batteries, and inverters, it makes sense to know how to pick all these items and why you should pick one over another. The costs of these equipment will also depend on how much power you expect from the system. While it is possible to invest in a solar power system for a single appliance like your refrigerator, it is advisable to set up your system in a way that it can easily accommodate more appliances in the future.

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