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How Many Batteries Do I Need for a 100 Watt Solar Panel?

Writen by Tom Hank

Fact checked by Joseph Varney

how many batteries do i need for a 100 watt solar panel

Solar panels can provide natural power to connected devices. They absorb sunlight and transform the energy into usable electricity. But you still need to store the collected energy in batteries.

Now, you’re wondering, “how many batteries do I need for a 100 watt solar panel?” Different factors can affect how many batteries per solar panel you need. But you should be able to get by with one battery for 2 days with minimal energy requirements.

However, you should consider your location and the frequency of use for the battery. If you need more power to run your devices, you may need more than one battery pack. Continue reading to know more about this need.

Table of Contents

How Many Batteries Do You Need for a 100-Watt Solar Panel?


The number of batteries required to power a 100-watt solar panel often depends on your location. If you’re still shopping for a battery for 100w solar panel, calculate your energy production by using the following formula:

Solar panel output = Solar panel wattage x average peak sun hours.

Now, let’s take a look at an example using that formula; for instance, you might be currently residing in New York City. That area should have about 4.2 hours of average peak sun hours. 100 watts multiplied by 4.2 hours is 420 watt-hours.

After acquiring the solar panel output, your next step is to find the right battery based on your requirements. Take note that batteries attached to solar panels often have ratings in volts and amp-hours. So, calculate the battery watt-hours using this formula:

Battery watt-hours = battery voltage x amp-hours

Now, consider a typical golf cart battery, which generally carries 6 volts and 200 amp-hours. Using those figures, the battery watt-hours is going to be 1,200.

Therefore, this battery can supply about 3 days’ worth of power.

Still, you should take note that batteries can degrade over time. If you’re using an old battery that underwent many charge and discharge cycles, you might only be looking at 50% to 60% of its optimal serviceability.

Therefore, that old battery may only supply about a day’s worth of power to connected appliances and electronics. Plus, you may need more batteries if you connect more devices to them.

What Can You Power With a 100-Watt Solar Panel?


A new and fully-charged battery with power from a 100-watt solar panel should allow a 10-watt LED to give light for about 10 hours. Another example is to use a 10-watt light for 3 hours, use an electric coffee maker, and listen to a radio for about 3 hours.

On the other hand, you can use a laptop for 2 hours straight without using anything else with the power supplied by the solar panel.

Here’s a list of other items that can take advantage of the power supplied by a 100-watt solar panel:

  • Cellphones
  • Lighting fixtures
  • Ceiling fans
  • Wi-Fi routers

Also, you need multiple 100W solar panels and higher-capacity batteries to power fairly large appliances. For example, the average refrigerator will require about three or four 100-watt solar panels. In turn, you need more panels to supply energy for other devices.

You can also watch the video below for a deeper explanation of the gadgets you can power with a 100-watt solar panel.

How Long Will a 100-Watt Solar Panel Take to Charge a 12-Volt Battery?

The duration in which a 100-watt solar panel can charge a 12-volt battery depends on the power pack’s amp-hour rating. For instance, a 12-volt battery with a 50 amp-hour rating will charge from 0% to 100% in about 8 hours.

Many batteries that are compatible with solar panels have frameworks that allow them to recharge and discharge for many cycles.

Take note that the maximum number of charging cycles differ for each battery. However, quality models can usually last for hundreds or thousands of charging cycles.

The discharge rating can also affect the charging time. For example, a 12-volt battery with the same amp-hour rating from the previous sample but discharged to about 50% capacity will become completely charged in approximately 4 hours.

What Size Inverter Do You Need for a 100-Watt Solar Panel?

If used with solar panels, inverters can provide additional functions. For example, some models can monitor the solar power conversion system.

You also need an appropriately sized inverter to provide AC power to connected devices. In other words, you can’t power electronic devices with a solar panel alone. Inverters convert direct current (DC) to alternating current (AC) electricity.

Buy and use an inverter with a capacity that’s 20% higher than that of your solar panel. Therefore, a 100-watt solar panel will need a 120-watt inverter at least. But it can be safe to use an even larger capacity inverter to avoid problems like power blowouts.

A 200-watt inverter connected to one 100-watt solar panel should do well to supply sufficient power to different electronics.

But keep in mind that the inverter only converts the energy. In other words, it cannot provide power if the battery connected to the solar panel runs out of energy.


Here’s a quick summary of what you should do to answer the question, ‘how many batteries do I need for a 100 watt solar panel?’

  • Calculate the solar panel output
  • Determine the battery watt-hours
  • Consider other factors that can affect battery life

Once you have those details, you can purchase the battery for your 100-watt solar panel with features that align with your energy requirements.

Additionally, if you already have a battery for your solar panel, you can use the information from your calculations to allocate energy usage around your residence more appropriately than before.

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