Solar power system requirements Run a Refrigerator for 24 hours

The refrigerator is one of the most important appliances in your home. It keeps food cold and fresh, preserves leftovers, and makes it easy for you to prepare healthy meals. How much power does a fridge run on and can you run your refrigerator on solar power?

Solar power system requirements Run a Refrigerator for 24 hours

In this article, we discuss the various wattages of refrigerators. We differentiate the starting and running watts of refrigerators.  We also discuss matching your fridge to an inverter, solar panel, and battery to make an off-grid setup

Solar Power for a 200-watt refrigerator

In order to calculate how long a battery will last with an appliance, we first need to consider the wattage of the refrigerator. Most modern refrigerators are rated at 200 watts this is as same as desktop computer. This figure is the running wattage of the refrigerator. The starting wattage can be 200-400 watts higher than this.

To run a 200-watt refrigerator you’ll need a 1000-watt solar panel or five 200-watt solar panels with a 24v 200Ah battery bank. This is enough to run your refrigerator for 24 hours on solar power. 

We take you through the math. 

Refrigerator Watt-hour requirements

When you are determining how much energy a device uses, you must consider the amount of time that it will be used. A Watt-hour is a product of multiplying a device’s wattage by its run time in hours. To calculate Watt-Hours you multiply the Wattage of the device or appliance and multiply by the number of hours you use the device. 

Watt-Hours = Watts X Hours 

If you want to use a 200-watt refrigerator for 1 hour you will need 200Wh, for 24 hours you need 4800 Wh or 4.8 kWh of energy. 

A fridge’s watt-hour requirements or Kilowatt requirements are usually indicated in the energy star rating. A 200-watt refrigerator will have a consumption of around 1575 kWh annually. Real figures may be higher or lower. This corresponds to the 4.8 kWh requirement per day. 

However, the starting wattage (power required for the compressor to turn ON and run) is twice the operating wattage of refrigerators. This could be around 600-800 watts depending on the model. 

The compressor will also be running at intervals of around 6-8 hours cooling the refrigerator. The defrost cycle turns the heating coils on for about 30 mins every 24 hours. This is all dependent on the brand, model, and size of the refrigerator.

With all that in mind, we still use the 4.8 Kwh to calculate the number of solar panels needed. 

How Many Solar Panels for a Refrigerator?

The size of the solar panel is dependent on the area, altitude, and how far you are from the equator. For example: If you’re in North America and want to charge an electric kettle using solar energy, then you would need a larger solar panel than if you were in Australia or South America.

This is why we use a ballpark figure of 4 hours as this would apply to everyone in any season. However, sun hours can last up to 6 to 8 hours in some regions. 

If you are in an area that receives around 4 hours of sunlight a day you will divide the total Watt-hour requirement by this number. 

In order to determine how many solar panels are needed for an electric kettle, we divide the total watt-hours required by the number of sun-hours we get in a day. So In the case, we are using the refrigerator for 24 hours you need around 4800Wh. 

An example is to use an average of 4 hours which could be high peak hours in the afternoon between 12 and 4. If you get more than 4 hours of sun per day, then use that number. 

4800Wh/4= 1200 Watts

A 1000-Watt solar panel or five 200-watt solar panels will be enough to provide around 4800Wh in the course of the day. 

What Size battery for a Refrigerator

There are two ways we can calculate the size of the battery needed to run the refrigerator. We can use the watt-hour requirements as we did with the solar panels or use the wattage of the refrigerator to get the amps. 

Using the Watt-hours to calculate battery size

To calculate Amp-hours you divide the Watt-hours by the voltage. 

The voltage in a battery bank is usually between 12v and 24v depending on how you wire the system. 

To find the size of the battery, you divide the watt-hours by the voltage. In the case, you have a 12-volt system, so you divide 900Wh by 12V and for the 24V system, you divide by 24V. 

4800/12 = 400 Ah

4800/24 = 200 Ah

So we’ll need a 12v 400Ah battery or a 24v 200Ah battery. 

However, there is something else to consider. How many amps is the refrigerator drawing and will our battery be able to support it? 

Using Running Watts to Size the Battery

Since there are two-wattage requirements for the refrigerator ( running and defrost cycle) you need a battery that can support the amp requirements for both

To get the amps you simply divide the watts by the voltage

Amps = Watts/Voltage

In a 12v system, the refrigerator will be drawing;

200/12 = 16.67 amps

200/24= 8 amps

For the defrost cycle it needs 600 watts however since it only lasts for 30 mins you half the wattage requirement:

300/12  =  25 amps

300/24  =  12.5 amps

So in a 12v system, the refrigerator will pull a total of 40 amps when running and using the defrost cycle and 16 amps when running normally. In a 24v system, the refrigerator will be pulling 8 amps when running normally and a total of 20 amps during the defrost cycle. 

In this case, it is better to go with the 24v 200Ah battery or two 12v 100Ah batteries connected in series. With the five 200-watt solar panels this system can run for 24 hours. 

Inverter for 200-watt refrigerator

An inverter converts the DC power from the battery to AC power that can be used by your refrigerator. When you are choosing an inverter you match the wattage of the appliance to the inverter. 

However, when matching your refrigerator to an inverter you need to be aware of the starting wattage. A 200-watt refrigerator will have a starting wattage of around 600 watts. 

For this refrigerator, you will need an inverter that is at least 800 watts. 

Conclusion 

One final note: if you’re looking to accomplish this yourself, keep in mind that this guide is an estimate. A refrigerator performs differently according to weather, location, and how much food is stored. You also have to take into account any spikes or surges that might occur. These calculations may be beyond the scope of this article, and we strongly suggest speaking with a professional before setting up your system.

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