One of the first things that many people think about when designing their own home solar power system is wondering how many panels they might need to power various home appliances. For some people, the shift to solar power is all about downsizing, while for others it is about offsetting their power consumption while still living a normal life.
For those who aren’t downsizing, one of the biggest questions is about their home refrigerators and how many solar panels it will require to keep them running. If you’re just looking for a quick answer, we can definitively say that for most average homes it will take 4-5 solar panels to power a refrigerator.
If you want to know how we came to that number, or how to calculate this for yourself, read on…
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How do solar panels work?
Solar panels, more formally known as photovoltaic modules, convert solar energy into usable electricity by way of the photovoltaic effect. When photons from the sun strike the surface of the solar panel, their energy is transferred to atoms that make up the materials of the panel and excite the electrons to move up to a higher energy state. These electrons are then gathered up and converted from DC electricity into AC electricity that is more commonly used in home appliances.
How to calculate how many solar panels you need
First, in order to calculate how many solar panels are needed for any given application, let’s assume that you have full sun, defined as an area that gets 6 or more hours of direct sunlight each day.
Next, you’re going to need to know the solar irradiance for your area.
Solar irradiance is the amount of energy from the sun that falls on any given one square meter of the Earth’s surface and measured in terms of watts per square meter. When time is added (for instance, one hour), then this is called insolation rather than irradiance.
Fortunately, it is easy to find out the average annual irradiance and insolation because most countries have some handy maps, like the one below, that show you the average numbers for your area. (Check out our other articles on the cost of solar in Ohio, Florida, or Arizona)
Now that you have an estimation for how much solar energy is available in your area, you’re going to need to look at what solar panel you have and what it is capable of producing. If your panel is capable of producing 300 watts each hour (Further Reading: What Can a 300 Watt Solar Panel Run?), but there are only 200 watts of solar energy available to be harnessed, then you will be limited by the sun that you get.
Meanwhile, if you live in an area with lots of sun then you may be limited by your solar panels and may need to add more.
Finally, you will need to know just how much power your device or appliance will be consuming each day. Fortunately, you’re in luck here – most major appliances state their power consumption right on the appliance, so you won’t have to go searching for this information.
So, with all of this information handy, now we’re ready to calculate how many solar panels you may need.
To help all this make sense, let’s use the example of a refrigerator.
How many solar panels do I need to power a refrigerator?
For this example, we’re going to assume that you live in an area of the country that gets an average of 5 kilowatt-hours (or, 5,000 watt-hours) per square meter per day. Around ⅔ of the United States gets this amount of solar energy daily, so there’s a good chance that this example will apply to you!
Next, let’s assume that you are using a standard size of residential solar panel, which comes in at about 1.6 square meters in size and has an output of about 250 watts per hour.
Finally, I went to Home Depot and picked out this standard refrigerator to use as an example. According to the energy guide, this model consumes an average of 410 kilowatt-hours per year, or 1.12 kilowatt-hours per day. Since we know there are 1,000 watts in a kilowatt, 1.12 kilowatt hours can be converted to 1,120 watts.
Now we have all the pieces we need to calculate how many solar panels are needed to power a refrigerator.
Since 5,000 watt-hours of solar energy is available to us, we know that there is more than enough solar power to run our 1,120 watt-hour refrigerator.
Since each solar panel has an output of about 250 watts per hour, we can divide 1,120 by 250 to end up with 4.48 solar panels needed. Since we can’t have .48 of a solar panel, we will round up and say that it takes about 5 typical solar panels to power a refrigerator.
Now, obviously, this is a very general estimation. How many solar panels you need to power a refrigerator depends on several factors:
- It depends on the power consumption and size of your fridge
- It depends on the output and efficiency of the panel
- It depends on how much sun you get and the time of year
All of these things can play an important role in designing your solar power system. If you live farther north, have lower efficiency solar panels, or have a refrigerator with higher power needs, you will need more solar panels to power your refrigerator.
Hopefully, I have shown you how you would go about calculating how many solar panels you might need to power a refrigerator and helped you to understand the process so that you can calculate your solar panel needs on your own.