How Much Solar Power Do I Need to Run a Refrigerator?
Refrigerators are one of the most essential appliances in any home. You need them to provide a cool place for your food to stay in, but they’re continually plugged in and need a lot of power to run. That's why many people think that it's just too much for solar panels.
However, with the right setup and enough solar panels, there's no reason why you couldn't run your refrigerator. You need to do some math and crunch some numbers first. After that, put your plan into action and take your refrigerator off-grid.
The Math
The logical starting point is to figure out how much power you need to run all the lights and appliances you want. That will tell you how many solar panels and batteries your system needs to power everything. You can do that in a few different ways.
The first one is to check the wattage of every device that will be connected to the solar panel grid. It's usually stated on stickers found either on the bottom of every appliance or near the power cord.
Sometimes it's displayed in amps, other times it's in watts. You can quickly convert amps (current) to watts (power) using this simple formula: P = VI (where P is power, V is voltage, and I is current).
For example, if your device is rated at 5 amps, that means that you need to multiply 120V with 5A to get a total of 600W. Repeat the same process for all devices and then add up the total power needed.
The second method requires a small device called an electricity usage monitor. It's a standard device in any electrician’s tool kit, and it tells you exactly how much power your appliances use. If you're not good with math and if you want to make sure that the numbers are 100% accurate, this device will help you a lot.
Most refrigerators use between 200 and 600W. If you can, get a model with an Energy Star for energy efficiency. Refrigerators tend to have higher draws when you turn them on, but the consumption goes down when they reach the optimum cooling temperature. When you've got that done, you need to consider all of the lights on the property.
How Long Will They Run
So, when you've figured out how many watts your appliances need to run, you need to consider the daily runtime. Your fridge will consume power for about 8 hours a day. An average 75W light bulb will run about three hours every evening. Let's say that you have five lights.
Add the numbers and list all consumers to get the final result that tells you how many daily watt-hours your grid needs to power everything. Here's a basic example:
Fridge needs 1800W
Lights need 400W
Other consumers need 600W
The total is 2,800W
Let's say that your grid needs 2,800W of power every day. That's still not the final consumption. Since the sun doesn't shine all the time, you need to consider the number of sunny days during a year. Multiply the total by three to get a more accurate estimation. So, multiply 2,800W by three and that comes down to 8,400W.
There are even more things to think about. The batteries of your solar power system should never go below 50%, which means that you have to multiply that number by two. The final power for our imaginary home is 16,800W or 16.8kW. That's enough power to keep your appliances working for three days without recharging.
The Size of the Battery
After considering all of the factors, you have to calculate the size of your solar battery bank in Ah (amp-hours). You can find out how many amps you need by dividing the final number with the voltage of the batteries.
In our case, that's 16,800W divided by 12, which is precisely 1,400Ah. Then divide that number with the rating of the batteries you will use on your system to find out how many batteries you need. Deep-cycle batteries have 300Ah capacity, which means that you'll need at least five to power your grid.
Many other battery types are even smaller, so you might need up to 10 batteries to provide the required 16.8kW of power. The last step is to calculate the number of solar panels you need to supply the power to the batteries.
How Many Panels Does Your System Need?
The last step is to calculate how many solar panels you need to provide enough power to recharge the batteries. You need to divide the total daily kWh with the number of sunny days. So, let's say you have a 75W panel that gets 5 hours of sun every day. That means that one panel produces about 375W or 0.375kW per day.
Now you have to divide the total daily usage with the production of a single panel. So, 2,800 divided by 375 is almost 7.5, which means that you need 8 panels for your system.
In the end, your planned system needs 8 solar panels and 5 batteries. If you get larger panels, you will need fewer. Everything depends on how much money you are willing to spend.
Do the Math and Power Your Fridge with Solar Panels
Since refrigerators are among the biggest consumers of power, you need to make sure that your solar power system has what it takes to run it. With a bit of brainstorming and a little math, you can easily find out how many panels and batteries you need to power your fridge together with the other consumers.