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Solar batteries can run lights, laptops, TVs and other appliances easily, but a fridge is another matter. They consume a lot of power and need more watts than other electronics. If you really want to live off the grid, knowing the answer to the question “how many batteries to run a refrigerator” is necessary. As you will see, a lot of variables are involved.
To run a 1000W refrigerator for 24 hours, it requires two 150Ah 24V batteries or two 300Ah 12V batteries. Modern refrigerators use 150-200W running, but on startup, a fridge needs 800-1000W. Power requirement also depends on how often you can recharge the batteries, its capacity and voltage.
Before You Calculate Battery Requirements
Before you calculate, answer the following. It will help you find the right specs for the battery, solar panel and the fridge.
- How many watts is your refrigerator?
- What is the battery capacity?
- Are you going to run the fridge on solar batteries all day, or for just a few hours?
- Does your battery have a constant power source?
- How long can you use the battery before recharging?
- How many other devices are going to use the battery running the fridge?
- How hot or cold is it in your location?
Some facts and figures to keep in mind when calculating:
- Refrigerator power is measured in watt hours (wh)
- Battery capacity is measured in amp hours (ah)
- Battery volts vary, with 6V, 12V and 24V the most popular. 12V is the “standard” but 24V is better in reducing energy loss.
- Always add 20% to the amount of power your refrigerator needs.
- Your solar panel must be able to provide the power the battery requires.
- You need an inverter, at least 1000W capacity.
- If you’re going to use the same battery to run other appliances besides the fridge, you have to include your total power requirements in the calculation.
How to Calculate Refrigerator Battery Size Requirement
Here’s an example:
You want to run a refrigerator that consumes 1000 watts a day for 24 hours. You are going to use a battery to run only the fridge. There are six hours of sunlight available and the weather is good.
You already know how much power in watts your refrigerator uses. You just need to find out how many amp hours of battery storage is required.
Watt hours / volts = amp hours
We also have to consider the inverter efficiency. Suppose the efficiency rating is 85%: Replace .85% with your inverter’s efficiency rating.
1000W / 0.85 = 1176ah
1176 ah / 12V = 98ah
If you use 24V batteries:
1000W / 0.85 = 1176ah
1176 ah / 24V = 49ah
So the figure we have is 100ah for 12V and 50ah for 24V batteries. However, you should recharge the battery before it drops under 50%. Meaning you’ll only be able to use half of the capacity. To run the fridge for 24 hours you have to double the battery capacity.
Doubling would mean a 200ah 12V or a 100ah 24V battery. So why did we say you need at least two 150ah 24V or two 300ah 12V battery earlier?
Because refrigerator battery calculations assume that the weather is ideal. We know that is rarely the case. Most of the time you’ll probably have to deal with cloudy skies that limit solar panel energy production. What do you do in those cases? During sunny days, you store up as much energy as possible and save them for cloudy and rainy days. That is where extra battery storage comes in.
And even if the day was perfect with the shining sun, solar panels cannot always produce the maximum power they are rated for. It can happen but only under rare circumstances, and you cannot depend on that for your fridge. That’s why it is better to have more power available in reserve. With two 300ah batteries you have more than enough to power your fridge even if the sky isn’t clear. You can also opt for three 200ah Renogy AGM batteries and get the same results.
Battery Power Plus Another Power Source
Because a fridge uses so much power, most solar panel owners rely on other power sources. You could run the fridge on propane or gas during the day and use a battery or a solar generator like the Bluetti Portable Power Station to run the fridge at night. You can do the same with solar panels. Use solar panels to power the fridge during daylight and let it charge the battery too. At night let the battery power the fridge.
To run a refrigerator, your solar panel must be at least 400W. You need more if you’re going to run other devices alongside it. You can already run a lot of electronics with a 400W solar panel, but a fridge is going to use all of that. This is why most RV owners assign a separate power source for the fridge.
The power requirements stated here are for 1000W refrigerators. More energy efficient and even solar powered refrigerators are now being developed. You can also opt for a mini fridge and save significant amounts in terms of power use.
Solar Panel Power is Important
If your fridge has another constant power source, you can run it on batteries only for as long as needed. If the battery is the main power source, make sure the solar panel array has sufficient power. An array consists of two or more solar panels joined together in a series or parallel. An array is necessary for running a good sized refrigerator along with other appliances.
A high battery capacity is useless if the solar panel cannot provide the power it needs. A solar panel cannot store its energy without a battery either so the two complement each other. If you have a 300ah battery, you should have a panel that delivers at least 1300W. Make adjustments to the solar panel size depending on how much power your fridge needs.
Can a 1000W Inverter Run a Refrigerator?
A 1000W inverter like the Renogy 1000W Pure Sine Wave can provide 2000W to 3000W surge power. That is enough for most refrigerators that need at least 1000W during the start. Once the fridge is running it only requires 150W to 200W, maybe 300W for powerful units. But even a 300W unit should not be a problem for a good sized battery.
Before you buy an inverter, check the surge capacity and compare it with your refrigerator. Some refrigerators require a 3500W surge, and that may not be enough for a 1000W inverter. You should buy a 3000W inverter if your fridge requires a lot of starting power.
The important thing to keep in mind is you need a powerful battery, inverter and solar panel to run a refrigerator. During sunny days your fridge should run fine. When the sun goes down, your battery has to be recharged. The inverter should set off an alarm notifying you of this.
Either use another battery to keep the fridge running or hook it up to another power source. This scenario assumes you are using the battery to power the fridge all day. This will not be a problem if you only run the fridge on battery during the night.
The good thing about modern refrigerators is they are more energy efficient than ever. Unlike old units that consume a lot of power, today’s units do not need too much power to start up the motor. The need for 2000W+ should come up only if you have a really large fridge. In that case it may be better to run it on electric power or gas so you can use solar power for other devices.
Look for a pure sine wave inverter for the best results. Also make sure that the battery is compatible with the inverter and can handle the power it generates. The best way to figure this out is to check the power requirement of your fridge and buy an inverter that matches or exceeds it. Do not buy an inverter with barely enough sufficient power, as it won’t be able to handle the motor.
Running a refrigerator on batteries requires a lot of batteries, but it is by no means impossible. With the right preparation and mindset, you can have a system set up that runs any fridge you want. Just like with anything solar, all it requires is careful planning.