How Many Solar Panels and Batteries for a 24/7 AC 115V Mini Fridge?

When considering powering a mini fridge using solar panels, the number of panels and battery capacity required depends on several factors, including the location's latitude, climate, season, and the fridge's energy consumption. This detailed guide aims to help you calculate the necessary components based on specific parameters and general configurations.

Understanding the Power Consumption of a Mini Fridge

A mini fridge typically consumes around 100-200 watts. However, to operate it 24/7 with solar power, you need to consider the following factors:

Sunlight availability Battery capacity Energy usage patterns Local weather and climate conditions

For example, a standard AC 115v mini fridge requires roughly 100 watts to run continuously. This power consumption can increase based on the type of fridge and its efficiency.

Calculating Solar Panel and Battery Requirements

Assuming the mini fridge consumes 100 watts, you would need one 250-watt solar panel. Solar panels do not work 24/7; they generate electricity only when the sun shines directly on them. On average, most locations have about 6 hours of peak sunlight per day.

Here’s the basic calculation:

To cover the entire day, you need 24 hours of electricity from the fridge. Given that the peak sunlight is 6 hours, the total energy required per day is:

100 watts/hour * 24 hours 2400 watt-hours or 2.4 kWh

Step 1: Calculate the solar panel capacity:

2400 watt-hours / 6 hours of sunlight 400 watts

Therefore, you need at least two 250-watt solar panels to meet this demand.

Step 2: Calculate the battery capacity:

2400 watt-hours - 250-watt panel * 6 hours 1800 watt-hours or 1.8 kWh

This means you need a battery with at least 1.8 kWh to cover the remaining 1800 watt-hours without sunlight.

Location-Specific Considerations

The number of solar panels and batteries needed can vary significantly based on the local climate and weather patterns. For instance, in areas with low sunlight like the PNW (Pacific Northwest) region, you may need a larger battery bank to cover extended periods of low or no sun.

Here are the general rules for calculating battery capacity:

Estimate the daily energy consumption during the months with the least sunlight. Decide how many days without sunlight you need to cover.

If you need to run the fridge for 10 days in low sunlight:

Lower demand solution: 0.64 kWh/day * 10 days 6.4 kWh (LiFePo battery) Higher demand solution: 3.13 kWh/day * 10 days 31.30 kWh (LiFePo battery)

Each 5 kWh LiFePo battery costs approximately $1500, and you might need to double the size for a lead acid battery.

Practical Applications

While the calculations provide a general guideline, specific requirements can vary. For instance, if you live in a climate like Seattle, where the weather can be drastically different month to month, you should size the solar array for the month with the least sunlight (like December). This way, you would have excess energy during the summer months.

I personally operate a 21-cubic-foot refrigerator on solar, but my battery bank is only sufficient for one day. In cases of low solar production, I use a generator as a backup.

To get a more precise estimate for your location, consider using the PVWatts calculator, which takes into account the specific conditions of your area.