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How Many Solar Panels Are Required to Run a Refrigerator?

Exploring the pros and cons of running your fridge with solar panels

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Carlos Huerta
Guide

When it comes to electricity consumption, refrigeration represents an important factor. Refrigerators are home and commercial appliances that are used to store and preserve food by cooling it at a specific range of temperature.  

If you are into solar energy, you might have wondered how many solar panels you need to run a refrigerator.

According to different studies, it is estimated that an average refrigerator requires about 3 to 4 average solar panels to be powered. Although, to have a more precise answer to this question, it is imperative to consider various factors: the refrigerator’s power consumption, the amount of solar energy available on your geographic location, and the power rating of the solar panels to use.

In this article, it will be covered the previously mentioned considerations, including some basic equations to calculate the number of panels.

How Much Energy Do Refrigerators Consume?

The usual way to estimate the energy that an appliance consumes is to check their power rate (Watts) on the technical specifications and multiply it by the hours of operation, obtaining a value in kilowatt-hours (kWh).

In this regard, if we have a constant 100W load working about 10 hours per day, we will obtain an electrical consumption of 1 kWh per day.

However, it would be inaccurate to apply this exercise when it comes to a refrigerator. Turns out that this type of appliance cannot be considered as a constant load because there are many factors that affect its operation, for example:

  • Usage habits: When the refrigerator´s door is frequently opened or kept open, the vapor compression cycle is forced, thus, the compressor consumes more power. Moreover, an empty refrigerator consumes more power than a considerably stocked one when the door is opened since more cool air is being replaced with warm air.
  • Type and size: Commercial refrigerators are bigger and consume more power than a home one.
  • Layout: if the fridge is in a warm location or has a lack of adequate ventilation, it will consume more power.
  • Climate change: In summer, refrigerators consume more electricity than in winter because ambient temperature rises.
  • Set point:  The standard temperature of the refrigerator, which is settled in factory, may be lower than your cooling requirements, thus, it will demand more power.
  • Age and condition: older refrigerators are less efficient than newer ones. Also, are less efficient those with poor maintenance.
Figure 1. Load curve of two different types of refrigerators. Source: Prayas (Energy Group)

In the matter of these previous factors, manufacturers usually provide an average annual energy consumption in the refrigerator specifications. Normally, it ranges between 200kWh and 600kWh.

In addition, technology has come a long way about refrigerators. In fact, it is imperative to mention that ultimately cutting-edge refrigerators have an Energy Star Label, which provides information about the efficiency of the appliance.

As a solar energy user, you will likely want to buy a highly efficient refrigerator by choosing one that has a high star rating, which will consume much less energy and save lots of money in your electricity charging bills.

How Much Sunlight Can I Obtain In My Location?

Measuring the amount of sunlight in your geographic location is an essential task in order to calculate how many solar panels you need to run your refrigerator.

There are several terms referred to the radiation produced by the sun and falling on the surface of the earth, however, the most important to our calculations is: the peak sun hours (HSP), which is a measure of the number of hours with a theoretically constant irradiance of 1000W/m2.

The peak sun hours should not be confused with the sunlight hours. Depending on your location and season, you may obtain 6-8 sunlight hours, but solar peak hours range from 3 to 6 hours.

Figure 2. Peak Sun Hours. Source: All Bay Solar

Nowadays, you can measure and forecast the sun peak hours, as well as other solar variables, in any location you want, by using online tools developed by specialized data centers, which collect solar and meteorological data to provide resources for renewable energy research. For instance, the NASA Power Project, an easy-to-use platform accessible for anyone.

Calculation Of Solar Panels Required To Power A Fridge

In order to calculate how many solar panels are required to run your refrigerator; you have to do some simple math, taking advantage of the values of solar peak hours and the energy demanded by the refrigerator, both discussed in the previous sections of this article.

To do this, you shall first calculate the DC power size of the PV system (kWp) by dividing the daily energy requirement (kWh) of your refrigerator by the multiplication of the sun peak hours (HSP) and a derating constant (associated to the panel losses) of 0.6 for off-grid systems. Thus, the equation must be:

After calculating the power size of the PV system, the next step for obtaining the number of panels required to power your refrigerator is simple. You only have to divide this last obtained value by the power rating of your selected solar panel. This results in the following equation:

In order to provide an illustrative example, consider a refrigerator with an annual average energy consumption of 600kWh, which is desired to be covered by solar panels, how many of them do I need?

Firstly, let’s go ahead and convert this value into a daily one as it follows:

We will assume that this refrigerator is located in California, therefore, as seen in figure 4, it is estimated to have 5 peak sun hours daily.

Figure 3. United States peak sun hours (HSP) map. Source: Unbound Solar

So, we will proceed to calculate the DC system power size using the formula (1):

Now, you must choose a convenient solar panel. As an example, we selected a highly efficient solar panel with a nominal wattage of 305W, from the US brand SunPower, as seen in figure 5. Now, applying formula (2), we obtain:

Finally, you’re all set by knowing the number of panels required to power your refrigerator. You can obtain the panel’s dimensions by searching into its datasheet; therefore, you can calculate the space that the PV system will occupy, and thus, estimate its average cost.

For the sake of simplifying all these calculations, you can take advantage of an online tool to design your photovoltaic system, for instance, NREL PVWatts.

Conclusion

Though refrigerators are getting more efficient overtime, their energy consumption is significant among common appliances. In this regard, going solar may be a great option for you when it comes to power your refrigerator, in terms of efficiency and costs.

Likewise, a common asked question by users that are involved with solar energy, is the exact quantity of solar panels they’ll need to buy and install to run their refrigerator or any other appliance.

So, after going through this article, you have the tools and resources needed to size your PV system. Nevertheless, it is always recommended to obtain professional consultancy from experts to do a more comprehensive analysis of your PV system requirements.

Frequently Asked Questions

Where Can I Find My Refrigerator Energy Usage?


When you’re about to buy a new refrigerator, it is highly important for you to pay attention to the energy star label because it provides valuable information about its efficiency and how much money you will spend on electricity bills in the long term.

You will notice the following characteristics in the energy star label:

–        Maker, model number, and size of the appliance.
–        Estimated yearly operating cost (based on the national average cost of electricity), and the range of operating costs for similar models.
–        The ENERGY STAR® logo indicates that this model meets strict criteria for energy efficiency.
–        Estimated annual electricity consumption.
–        Key features of the appliance and the similar models that make up the cost comparison range.


 
Figure 4. Energy Star Rating Label. Source: U.S Energy Department

Can I Run My RV’s Refrigerator Using Solar Panels?



The answer is yes. Just as any other refrigerator, you only need to follow the analysis that we did through this article.

An important detail to consider for RV’s is that you may need to select lower wattage solar panels of 100W-200W. This is common in most applications due to the limited roof space. It is also recommended to use a tilt mounting kit for your solar panels to get the best possible performance  

Which Components Do I Need In Addition To My Solar Panels To Run My Refrigerator?


Solar panels produce DC power, but refrigerators run on AC power. Therefore, it is essential to have an inverter device that provides the AC output needed. In other words, as with multiple off-grid systems, you will require solar panels, charge controller, battery bank and the inverter.

 
Figure 5. PV System for an RV. Source: Camper Upgrade

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Author Bio

Electrical Engineer with background in solar PV designs for residential and commercial projects as well as power systems development. Fan of renewable energy topics and projects. Technical writer for papers, articles and research in related topics to sustainability and especially solar power.

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