The refrigerator is one of the most energy-intensive appliances in most homes. Unlike most appliances, the fridge runs 24 hours a day, 365 days a year, making them the single most significant energy consumer in most homes. Considering this high demand, someone thinking about solarizing their home may wonder how many solar panels they would have to get to power their fridge.
So, how much solar power do I need to run a refrigerator? The average fridge in the United States needs between 350-2,000kWh a year to operate. This typically translates into 1-4 solar panels. The amount of solar power needed to run a refrigerator depends significantly on the age, and model of the fridge, given that newer fridges can consume less than half the energy of older ones. It also depends on the panels used and how much sunlight they get. For example, a 100-watt panel in New England will produce far less energy than a 500-watt panel in Arizona.
This article will go into greater detail about each of these considerations. We’ll be looking at just what it takes to power a fridge in a solarized home. We won’t look specifically at more portable panels to power the refrigerator itself detached from the house (mainly because the considerations won’t be much different). We also won’t talk about how much energy it would take to power the whole home (even though it doesn’t make much sense to install the panels needed for just the fridge and nothing else).
How Much Energy Does My Fridge Consume?
The average refrigerator in the US consumes between 350-780 watts a year. Of course, this varies substantially depending on the make, model, and how old the fridge is.
A full-sized fridge/freezer will consume much more energy than a simple mini-fridge. And a newer, high-efficiency model will consume much less than an older, less advanced one.
To calculate how much solar power you need, you’ll have to figure out your specific model’s total consumption. Fortunately, there are several different ways you can go about doing this.
The Energy Guide Label
One of the easiest ways to find your model’s consumption is to find the Energy Guide label. Since the 1980s, appliance manufacturers are required to feature one of these labels on their appliances. It’s yellow and black, typically affixed to the back, and details the annual energy requirements in kWh and an estimated annual cost of operation. The kWh number is what you want to guide your assessment of solar panels.
However, if you have an older model, it likely will not have one of these labels. So if your model is too old, or if the label got ripped off at some point, you’ll have to use another method.
The Quoted Power Rating
The quoted power rating is found on a different label from the Energy Guide label. It basically presents an older version of the same information as the Energy Guide label–an estimate of annual electrical use for that appliance–just without the annual price estimate.
A refrigerator’s quoted power rating is listed with the serial number and can be found either on the back or inside the fridge. Unlike the Energy Guide label, older models will include a quoted power rating.
The information on the quoted power rating may be presented in watts or just volts and amps, so you may have to do a little conversion to compare it with solar panel output.
If you can find a watt number, compare that with the listed wattage or kilowattage of solar output. However, you’ll have to calculate if your rating is given in volts (written as VAC, volts of AC current) and amps without a wattage listing.
To determine wattage, multiply the voltage by the amperage (Volt x Amp = Watt).
Here’s the calculation for my refrigerator: 110 VAC x 6.5 Amp = 715 watts
Other Published Information
If you can’t find these labels, you can always look up the power rating on the manufacturer’s website using the specific model name. To get accurate results, you’ll likely need to use the serial number.
The serial number is typically on the same label as the quoted power rating, so this method might just be adding an unnecessary step. Also, if your fridge is old enough, this information may no longer be readily available on the internet. For example, it may be a discontinued model, or the manufacturer may no longer exist.
If you are one of those rare people who keeps instruction books, you may also be able to find the power rating in there.
Now that you know the power requirements of your fridge, it’s time to find the correct number and type of panels.
How Much Energy Can a Solar Panel Produce?
Solar panels come in many shapes and sizes, capable of providing a wide range of power generation. Small, portable panels can produce as little as 5 watts, and larger, house-sized units can produce up to 500 watts.
But what do those ratings mean?
The power rating of a solar panel is an assessment of the amount of power it produces in a single hour on a perfect day. For example:
● A 300-watt panel produces 300 watts an hour
● A 400-watt panel produces 400 watts an hour
Looking at this chart, you may think you can simply multiply the wattage by your total daylight hours and get your total for the day. But not quite…
Solar power, as advanced and robust a technology as it is, is still remarkably inefficient and needs ideal circumstances to produce much electricity.
Solar specialists speak in terms of “peak hours” – the hours when the sun is at its highest point in the sky and gives off the most energy. Solar panels can only reach their rated output during these times, and this peak time typically lasts only 4-7 hours a day, depending on where you live. The panels may produce electricity outside peak hours, but the output will be much less than advertised.
This means that a 300-watt panel will only produce 300 watts an hour during peak hours. Considering there are usually only 4-7 hours of peak a day, you can realistically expect 1200Wh-2100Wh or 1.2kWh-2.1kWh of energy production a day under ideal conditions. You can calculate the daily amount of power generated by any panel rating in any given location.
So let’s talk about location.
How Much Will a Solar Panel Produce in My Area?
There is incredible variation in sunlight throughout the United States. Places like Arizona and southern California can expect up to 7 peak hours a day on average, whereas someplace like New England usually only gets 4.
Here’s a breakdown of the daily peak sun averages by United States region:
● Northeast: 4
● Midwest: 4.5
● South: 5.5
● West: 6.8
Of course, these numbers are gross generalizations. Exposure to peak sun for an individual property will depend on several other factors, like whether or not you’re on a hill, surrounded by trees or other buildings, near larger mountains, etc. You’ll need to consult with a local solar authority to understand better what you can expect from your situation.
How to Power My Refrigerator at Night
A key thing to remember about solar power is that it can only produce energy during the day. At night, you will get no electrical production from it.
Unless you have a storage device like a battery, electricity is consumed as soon as it is produced. Without a way to store it, the electricity that isn’t immediately consumed or sent elsewhere to be consumed won’t stick around – it’ll just dissipate.
Most solarized homes are attached to the grid for this reason. Any excess power produced during the day gets sent to the grid for other houses and businesses to use. Then at night, when the panels aren’t producing electricity, the solarized home can draw power back off the grid.
The grid operator keeps track of how much that house contributes to and draws from the grid, so you only have to pay if your overall consumption outpaces your panels’ overall production. Off-grid homes don’t have this backup system, so they need a battery to get them through the night.
What this all means: to power a refrigerator in both on-and off-grid houses, your panels need to produce enough electricity in 4-7 peak hours to power your fridge for 24 hours.
For off-grid houses, they also need to consider the time and power required to charge their batteries. Like the panels themselves, batteries have inefficiency problems that will impact your requisite number of panels to power your fridge.
Since solar batteries operate on DC power (whereas appliances operate on AC power), an inverter is needed to convert the electricity between the two. Unfortunately, energy is lost in this conversion process, meaning you’ll get less power out of the battery to run the fridge than the solar panels put into it to charge it.
A paper published by the University of Texas at Austin demonstrated this total loss to inefficiency to be about 15%. So, you’ll need an even higher power output from the panels than you would in an on-grid system.
Example Production Amounts
Let’s look at a few general examples to see the impact that a panel’s size and location make on its production and battery loss. These calculations will be based on one refrigerator, so the numbers would undoubtedly need to be adjusted for more than one.
Say I live in Seattle, Washington, where I only get 3.9 hours of peak sunlight a day. If I have a 100-watt panel at 100 watts per peak hour, I can expect only 0.39kWh a day. Multiply that by 365 days a year, and my 100-watt panel produces 142kWh a year. Given our range of 350kWh-2,000kWh needed for most fridges, I would need between 3 and 14 panels to do the job.
Now, at the same location with a 300-watt panel, I’d get 1.17kWh a day. Multiply that by 365 days a year, and my 300-watt panel produces 427kWh a year. One panel would do the job for some modern refrigerators, but I could need up to 4 more (up to 5 total) depending on the fridge.
Alternatively, if I live in Phoenix, Arizona (where I can expect 6.6 peak hours a day), a 100-watt system would yield 6.6kWh a day. Multiplied by 365 days a year, that’s 240kWh a year. I’d need between 2 and 9 100 watt solar panels to run a refrigerator in Arizona, compared to 3-14 in Seattle.
A 300-watt system in Phoenix would yield 1.98kWh a day. Multiplied by 365 days a year, that’s 722kWh a year–enough to power most new model refrigerators with a single panel and older models with up to 3.
Finally, if I take the last example (a 300-watt panel in Phoenix), but put it in an off-grid system with a battery, I’d lose about 15% of my energy production. My daily production would be reduced from 1.98kWh to 1.68kWh. This daily reduction means my yearly production would be 614.3kWh, over 100kWh less annually than my on-grid counterpart. Still, enough for newer fridges but requires up to 4 panels for older ones.
Recap: Amount of Solar Power Needed to Run a Refrigerator
Many factors contribute to how many solar panels you’d need to power a fridge:
● You first need to find out just how much power your fridge consumes.
● Then you’ll need to look at the power output of a panel and the number of peak hours where you’re installing it.
● If you’re using a battery, you also need to consider the loss to inefficiency and increase your requisite power output accordingly.
● When all of these forces have been balanced, you determine how many panels you need to power your fridge.