What Size Solar Panel To Charge 12V Battery (& How Long Each Size Takes)

Georgette Kilgore headshot, wearing 8 Billion Trees shirt with forest in the background.Written by Georgette Kilgore

Solar Panels | March 15, 2024

Man looking at solar panels connected to a 12v battery and wonders, what size solar panel to charge 12v battery, how many solar panels to charge 12 volt battery and can you charge 12v battery with solar panels?

When you are putting together a solar energy system, one of the most common questions that you stumble upon is what size solar panel to charge 12V battery?

Since batteries are an essential part of most home solar panel installations, knowing how long it takes to charge this size battery is an important part of building the energy system.

Unfortunately, there is not a one-size-fits-all answer. The length of time and what size solar panel to charge a 12V battery depends on the location where the system will be installed (the amount of sunlight you get).

In order to help you navigate through these difficult questions, here is a quick guide to know how to pick solar panels to charge 12 volt battery.

By going through the following information, you can learn what size solar panel to charge 12V battery and how long each size takes.

Understanding the Basics: Why Should You Use Deep Cycle Batteries for Off-Grid Use?

As compared to traditional batteries, deep cycle batteries provide you with steady levels of energy for longer periods of time, without affecting the health of the battery.

The depth of discharge (DoD) or the level at which deep cycle batteries can be discharged against their full capacity is also higher than traditional batteries.

Photograph depicting a set of deep cycle batteries positioned alongside a solar charge controller.

(Image: Cody Kabus, U.S. Department of Energy8)

Typically, deep cycle batteries can be discharged for up to 80% of their total capacity, which makes them boast of a deep discharge feature that is out of reach for traditional batteries.1

With that being said, for a longer battery lifespan, you should mostly use your deep cycle batteries at 50% DoD or lower.

Due to this reason, home and office energy systems for off-grid power use deep cycle batteries.

This is also why you need to utilize deep cycle batteries in your solar energy systems before you learn how to test a solar panel system’s output.

How Do You Charge 12V Battery With Solar Panel? (What Size Solar Panel To Charge 12v Battery?)

You can use solar panels to charge 12 volt battery by using sunlight as a source of energy. Your solar panel absorbs sunlight and delivers it to your battery as direct current (DC). Your battery stores this energy according to its capacity.

You can then use an inverter, which comes with your solar energy system, to convert this DC into alternating current (AC). This directs the required power to your electronic devices and appliances through your solar panel system.

Of course, it can be somewhat complex and difficult at first, at least it will appear that way, but when you conduct it a few times, you begin to realize that it is not so bad at all. A great point is that it is about simple learning and then practicing it.

Then you will realize the process and it will be as if it is second nature to you. While battery capacity is calculated in amp hours (Ah), you can convert it to watt hours (Wh) if you know the voltage of the battery.

When shopping for batteries, you can notice that their capacity is measured in amp hours (Ah). But if you are aware of the battery’s voltage, you can convert these amp hours to watt hours (Wh).

For this purpose, you can use the following equation:

Volts x Ah = Wh

Let’s say that you have a 200Ah 12V battery. Calculation below:

12V x 200Ah = 2400Wh (2.4kWh)

Through this process, you can determine what level of Ah in a 12V battery will meet your energy requirements.

How Long To Charge 12V Battery With Solar Panel?

A few factors will determine how long it takes for your solar panels to charge 12 volt battery.

Photograph showing a 12-volt solar panel battery on a grassy ground with bush behind it.

(Image: Newpowa9)

This includes the energy capacity of the 12 volt battery that you have at hand, the amount of peak sun hours that you receive at the installation site, and the overall output of the solar panels that you use.

This is how each of these factors influence the time it takes to charge 12V battery with solar panel.

Battery Capacity

12V batteries come in a variety of energy storage options that are calculated in amp hours. Gel, lead acid, and lithium-ion batteries are some of the most popular battery options for off-grid energy storage.2

Many off-grid systems can also include multiple batteries at once to meet your energy requirements.

A battery with a higher energy capacity takes more time to charge than one with a lower capacity. But you cannot choose a battery based on the time it takes to recharge alone.

Instead, you have to account for how the battery’s offered capacity caters to your specific energy requirements for off-grid applications.

Peak Sun Hours

This term outlines how much daily sunlight your solar panel gets on a normal day. If your solar panel receives full sunlight that is not obstructed by any type of shade, it can recharge faster.

On the other hand, any obstructions between the sun and your solar panel can negatively influence your solar panel output. Knowing about this information can help you answer how many solar panels do I need.

Your solar panel energy system provider can take a look at your installation site and determine if your solar panels may face occasional obstructions because of the weather or constant shade due to any structures around it. Afterwards, they can let you know how many solar panels you will need for optimal efficiency.

Output of Solar Panels

The wattage of your solar panel also has an effect on the speed of your battery recharge. For example, if you have a 50-watt solar panel, it may take twice the time to recharge your battery as compared to a 100-watt solar panel.

In a similar fashion, a 200-watt solar panel may recharge your 12V battery in half the time of a 100-watt solar panel. Due to this, it could lead you to use multiple panels of 100-watt, 200-watt, or 300-watt in a single set up.

Proper comprehension of the above helps you know how to use setups such as battery 12V, and solar panel 100W systems for off-grid use. This way, you can discuss your requirements with your solar panel provider, understand the technicalities of the process, and make informed decisions about your renewable energy setup.

Knowing these factors lets you obtain an informed opinion about what size solar panel to charge 12V battery (& how long each size takes). You can then learn how much do solar panels cost in your state and get an idea about the price of your solar energy setup.

What Size Solar Panel To Charge 12V Battery?

You can use many common sizes of solar panels to charge 12-volt battery.

But the ideal size depends upon your overall energy requirements.

Photograph depicting two solar panels propped up in front of a tree.

(Image: Newpowa10)

For instance, if your daily energy usage matches that of an average U.S. household at 29.8kWh per day,3 you will need a collective battery capacity of at least 2400Ah to fulfill your needs. But if you have a lower energy requirement, a few 200Ah batteries may do the trick.

To fully recharge a 200Ah battery after using 80% of its capacity, you may need at least one 300-watt solar panel at peak sun hours every day.4 It is because a 300-watt solar panel could provide you with 2.1 kWh of power a day if it obtains energy for 7 hours a day in full sunlight.

This could help you recharge your 200Ah battery with ease.

Alternatively, you can also use three 100-watt solar panels to fulfill the same requirement. With that being said, in order to make up for cloudy days, you may ideally require two 200 watt solar panels or one 400-watt solar panel to fully meet your needs.

This helps your installed solar panels to charge 12-volt battery without running into unwanted issues. You can get a general idea of how long to charge 12V battery with solar panel by looking at the following table.

Solar Panel Wattage (Watts) Hourly Output (Peak Sunlight) Time To Charge 55Ah 12V Battery Time To Charge 200Ah 12V Battery
100 100 Watts Approximately 6 Hours Approximately 21 Hours
250 250 Watts Approximately 2.5 Hours Approximately 8.5 Hours
300 300 Watts Approximately 2 Hours Approximately 7 Hours
350 350 Watts Approximately 1.75 Hours Approximately 6 Hours
400 400 Watts Approximately 1.5 Hours Approximately 5.25 Hours

Graphics of solar panel output comparison on bar graph with solar panel wattage and hourly output in watts on the x-axis and time to charge on the y-axis.

These details give you an approximation of what size solar panel to charge 12V battery (& how long each size takes). From there, you can use this information to find a solar panel setup that works for your needs.

What Is the Best Solar Panel for 12V Battery? How To Obtain Great Solar Panels To Charge 12 Volt Battery

You can look into a green power equivalency calculator to determine factors such as daily energy needs and capacity of your panels.5 You may contact your local solar energy system provider to get precise suggestions.

The best solar panels to charge 12 volt battery vary on a case to case basis.

It is a great idea to look at these different aspects as you are searching for a fantastic solar panel for your needs. The more information you have enables you to make a wise decision when it comes to these energy needs.

Further, your energy needs will always be there and might grow with the advances present in appliances and technology and thereby calls for even more attention to these power sources.

Charging Tesla With Solar Panels: How Many Solar Panels Do I Need for an EV?

You can charge your Tesla with solar panels.

But you may need multiple 400W solar panels to recharge your Tesla with renewable energy, but without investing an excruciating amount of time in the process.

Photograph depicting a Tesla car charging using a solar panel system.

(Image: Kindel Media11)

You can determine how much energy is used by your Tesla model and plan your solar panel system according to that.6

Indeed, turning to the right calculator can help. One that tells you how to start charging Tesla with solar panels will be very beneficial.

How To Wire Solar Panels

Learning how to wire solar panels requires some technical knowledge.

You will find that in this process, there are solar panels and a few other items to watch for as well. For instance, think of a charge controller, and an inverter, too.

Photograph depicting a man making adjustments to the wiring of a solar panel. He is wearing safety equipment.

(Image: Los Muertos Crew12)

Knowing how the shading effect works with solar panel installation is also crucial.7 To minimize stress, go with professionals who know how to wire solar panels as they do it regularly.

What Is the Carbon Footprint Solar Panels Have on the Environment?

The carbon footprint solar panels have on the environment mostly comes from the materials used within them and the manufacturing practices that are utilized to make them. Typically, solar panels offset their carbon emissions after a few years of being used.

You can go through a carbon footprint solar panel guide to gain more information about this.

Can an Individual Use a 12V Solar Panel To Charge Deep Cycle Battery?

It is possible to use a 12V solar panel to charge deep cycle battery. Experts in this sector will suggest that you take this approach because it provides better results.

Remember, when setting up solar panels to charge 12 volt battery, it is best to take this into consideration.

After learning how to charge 12V battery with solar panel, you can be more confident in asking your solar panel system provider for personalized recommendations.

This lets you know exactly what size solar panel to charge 12V battery would cater to your requirements and how you can adopt renewable energy for a more sustainable lifestyle.

Frequently Asked Questions About What Size Solar Panel To Charge 12V Battery

What Size Solar Panel To Charge 12V Battery: Can You Use a 5W Solar Panel To Charge 12V Battery?

Yes, you can use a 5W solar panel to charge 12V battery. Be aware, it may be require more time.


1MIT Electric Vehicle Team. (2008, December). A Guide to Understanding Battery Specifications. Massachusetts Institute of Technology. Retrieved April 11, 2023, from <https://web.mit.edu/evt/summary_battery_specifications.pdf>

2Shapley, P. (2012). Common Battery Types. University of Illinois. Retrieved April 11, 2023, from <http://butane.chem.uiuc.edu/pshapley/GenChem2/C6/3.html>

3United States Geological Survey. (n.d.). How many homes can an average wind turbine power? USGS science for a changing world. Retrieved April 11, 2023, from <https://www.usgs.gov/faqs/how-many-homes-can-average-wind-turbine-power>

4Renogy. (2022, February 9). What size solar panel do I need to charge a 12v battery? Renogy Find Your Energy Freedom. Retrieved April 11, 2023, from <https://www.renogy.com/blog/what-size-solar-panel-do-i-need-to-charge-a-12v-battery/>

5United States Environmental Protection Agency. (2023, February 5). Green Power Equivalency Calculator – Calculations and References. EPA. Retrieved April 11, 2023, from <https://www.epa.gov/green-power-markets/green-power-equivalency-calculator-calculations-and-references>

6Decker, B. (2023, January 5). How much electricity does it take to charge a Tesla? LECTRON. Retrieved April 11, 2023, from <https://ev-lectron.com/blogs/blog/how-much-electricity-does-it-take-to-charge-a-tesla>

7Chaaban, M. A. (n.d.). Wiring within a PV Module and the Shading Effect. PennState. Retrieved April 11, 2023, from <https://www.e-education.psu.edu/ae868/node/875>

8Deep cycle batteries Photo by Cody Kabus for the U.S. Department of Energy / Public Domain. Flickr. Retrieved from <https://flic.kr/p/Y2Lie3>

9Newpowa. Unsplash. Retrieved from <https://unsplash.com/photos/xjzCtZN4i6I>

10Newpowa. Unsplash. Retrieved from <https://unsplash.com/photos/ke0BJJ9Kmp8>

11Kindel Media. Pexels. Retrieved from <https://www.pexels.com/photo/white-electric-car-charging-9800024/>

12Los Muertos Crew. Pexels. Retrieved from <https://www.pexels.com/photo/maintenance-man-working-on-site-8853471/>