How Many Deep Cycle Batteries to Run a Refrigerator is Needed?

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To run a 1000 watt refrigerator for 24 hours, it requires two 150 amp hour 24 volt batteries or two 300 amp hour 12 volt batteries. Modern refrigerators use 150 to 200 watts running, but on startup, a fridge needs around 800 to 1000 watts. Power requirement also depends on how often you can recharge the batteries, its capacity and voltage.
Before you calculate battery requirements, you have to answer the following questions. It will help you find the right specs for the battery, solar panel and the fridge.
1. How many watts is your refrigerator?
2. What is the battery capacity?
3. Are you going to run the fridge on solar batteries all day, or for just a few hours?
4. Does your battery have a constant power source?
5. How long can you use the battery before recharging?
6. How many other devices are going to use the battery running the fridge?
7. How hot or cold is it in your location?
Some facts and figures to keep in mind when calculating:
1. Refrigerator power is measured in watt hours
2. Battery capacity is measured in amp hours
Battery volts vary, with 6 volts, 12 volts and 24 volts the most popular. 12 volts is the "standard" but 24 volts is better in reducing energy loss.
Always add 20% to the amount of power your refrigerator needs. The cushion is essential not just with refrigerators, but any appliance or electronics you will run on solar panels and solar deep cycle batteries.
Your solar panel must be able to provide the power the battery requires.
You also need an inverter with at least 1000 watt 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.
So How do you Calculate Refrigerator Battery Size Requirements?
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 deep cycle 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. The formula is:
Watt hours divided 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.
1000 watt divided by 0.85 = 1176 amp hours
1176 amp hours divided by 12 volts = 98 amp hours
If you use 24 volt batteries, the formula is:
1000 watts divided by 0.85 = 1176 amp hours
1176 amp hours divided by 24 volts = 49 amp hours
So the figure we have is 100 amp hours for 12 volts and 50 amp hours for 24 volt 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 200 amp hour 12 volt or a 100 amp hour 24 volt battery. So why did I say you need at least two 150 amp hour 24 volt or two 300 amp hour 12 volt 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 300 amp hour batteries you have more than enough to power your fridge even if the sky isn't clear. You can also opt for three 200 amp hour AGM batteries and get the same results.
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 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 400 watts. You need more if you're going to run other devices alongside it. You can already run a lot of electronics with a 400 watt 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 1000 watt 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.