You don’t want to waste money on a large inverter. After all, these devices become more expensive the larger they get. And mini-fridges are not like full-size fridges. They only use a fraction of the power a full-size refrigerator consumes.
On the other hand, a small backup system will overload if the mini-fridge exceeds its capacity. This is why selecting the correct inverter for a mini-fridge is so important. To accomplish this task, you must consider the following variables:
1). Start With Mini-Fridge
The appliance’s power consumption will influence the inverter’s rating. But how many watts does a mini-fridge use? The Daring Kitchen associates the device with an average of 50 to 65 watts, which is appealing because it amounts to less than 1 amp.
Inverters are powerful enough to run heavy-duty items such as pumps and air conditioners. They will make short work of a mini-fridge. The following factors will influence a small fridge’s energy consumption:
Retailers sell mini-fridges in various sizes. Naturally, smaller appliances have a lower energy consumption. The larger the fridge, the more watts it will use. Conserve-Energy-Future has given the example of a 1.6/1.7 cubic feet mini-fridge that uses 70 to 100 watts. This is the smallest size on the market.
70 watts equate to 0.58A (120V). That figure rises to 2A or less for 3.2 cubic feet. The model matters. Some 1.7 cubic feet fridges may use more or less energy than others.
Did you know that aging affects energy efficiency? This study in Applied Thermal Engineering (Volume 205) investigated this subject. Previous studies had already revealed that various technical aging mechanisms increased energy consumption by 36 percent over a product’s 18-year lifespan.
This new study looked at 11 new appliances and noted that their energy consumption increased by 11 percent in just two years. Another set of 21 appliances had been tested while new. Twenty-one years later, their energy consumption had risen by 28 percent.
If you still have doubts, Mark J. Perry has noted in this American Enterprise Institute article that newer appliances have superior energy-saving technologies to their older counterparts. Admittedly, a mini fridge’s rising energy consumption won’t affect the inverter you select because the wattage will remain largely unchanged. However, the rising energy consumption will influence the runtime.
- Consumer Behavior
This is another variable that affects the runtime but not necessarily the inverter size. This study in Energy Policy (Volume 155) polled 706 consumers in Germany and found that consumer behavior had a significant impact (32.5 percent) on an appliance’s power consumption.
For instance, keeping the door open can increase the volume of power a mini-fridge uses. Again, you can’t overload an inverter by forgetting to close the door or allowing the door seal to deteriorate. However, the runtime will reduce drastically.
Where inverters are concerned, you only have two significant factors to consider:
- Inverter Type
You can choose between pure sine wave, square wave, or modified square-wave inverters. Technicians usually pair pure sine wave inverters with sensitive electronic devices that require a clean and stable power supply.
People flock to this type because of its efficiency, longer lifespan, and quiet operations. You can settle for a modified square wave inverter to save money. However, you should expect choppier transitions in the AC output.
The modified square wave inverter cannot produce the same sophisticated power conversions you find in its pure sine wave counterpart. This means appliances with motors will consume more energy because the motors are running hotter than what you see with pure sine wave inverters.
Here, you have three ratings to consider. The first is the continuous power rating. As the name suggests, this is the wattage the inverter can output continuously. An inverter’s wattage tells you the continuous power rating. For instance, a 3000W inverter can run any device that requires 3000 watts or less.
What about the surge rating? Appliances with a motor can easily use three to seven times their running wattage when they cycle on. What happens when you connect a 3000W mini-fridge to a 3000W inverter?
The inverter can run the mini-fridge during normal operations. However, that fridge will overwhelm the inverter when it cycles on. This is why the surge rating matters. It accounts for that initial spike in the electrical draw. You should base your selection of an inverter on both the continuous and surge ratings.
- Input Voltage
An inverter cannot run your mini-fridge alone. Conventional backup systems use batteries to operate your home’s appliances during a power outage. However, batteries generate direct current, while your mini-fridge needs alternating current.
The inverter turns a battery’s direct current into alternating current, which the mini-fridge can use. It performs the same task when you connect it to solar panels. Are your batteries compatible with the inverter’s voltage?
According to Enogy, inverter inputs are 12V or 24V. Make sure the batteries are compatible with the inverter’s input voltage before you buy it.
3). Calculating The Size Of The Inverter
- Find the wattage of the mini-fridge. Check the nameplate or manual.
- Turn the wattage into amps. Dividing the wattage by 12V will give you the DC amperage.
- Determine the inverter’s efficiency and divide it by the wattage of the appliance. For instance, if the inverter’s efficiency rating is 80 percent and you have an 800W device, divide 800W by 80% to get 1000W.
- The efficiency rating tells you how much power will flow from the battery to the appliance. If you only expect 80 percent of the power to reach the load, you must increase the current flowing from the battery through the inverter to the load. In the example above, even though the appliance has a wattage of 800W, you should take 1000W as the load, not 800W.
- Dividing 1000W by 12V will give you the DC amperage (83A).
At this point, you can select an appliance that exceeds 83A. In the case of a mini-fridge, the inverter’s rating should exceed the starting wattage.
Does The Battery Capacity Matter?
Yes, the battery capacity matters because it determines the runtime. For instance, the experts at SF Gate Home Guide expect lead-acid batteries rated at 105-ampere hours to run a fridge with 55 DC amps continuously for 60 minutes.
But if the power outages in your area have a reputation for lasting multiple hours, that 105 ampere-hour battery won’t help you. If the Centers for Disease Control and Prevention is to be believed, food will stay safe for up to four hours in a fridge without power.
Therefore, you need a larger battery capable of running your mini-fridge for the duration of the outage. Keep in mind that draining lead-acid batteries completely is discouraged. In fact, from what Rebel Cell has seen, you can do irreversible damage to lead-acid batteries by discharging them beyond the 50 percent mark.
Therefore, the battery capacity is just as crucial to the batteries as it is to the mini-fridge. Where possible, select batteries capable of operating the appliance for the required duration while staying above 50 percent.