How Many Watt Solar Panel to Charge Deep Cycle Battery?

How Many Watt Solar Panel to Charge Deep Cycle Battery?

As solar technology has become more accessible in recent times, many people have found it more convenient to go entirely off major power grids. If you can manage to achieve this feat, it would imply an independent energy source, albeit dependent on some factors. In addition to the positive impact of solar power on the environment, you get to be independent of the public power utility.


The major components of a solar system are the panels and rechargeable batteries. What can be confusing is figuring out how many watt solar panel to charge deep cycle battery. I hope to put you through the process of calculating your solar requirements whenever you are ready to set up your sustainable solar system.

What Is a Deep Cycle Battery?

In solar energy systems, deep cycle batteries are typically lead-acid batteries designed to have a significant percentage of the capacity discharged. The sun as a renewable energy source produces instant energy, and it does not do so intermittently. So, you need batteries that can store up the instantaneous power so that you can access it at a later time.

How to Calculate Your Solar Panel Specification?

You don't want to set up an off-grid solar system that will underperform, and you certainly don't want the system to be stressed out. So, it is imperative that you accurately establish the specifications before setting up. Before you determine how many watt solar panels you need, you first have to consider the battery capacity.

1. The Amount of Energy the Battery Can Store

A very significant factor that affect battery functionality is capacity. The battery capacity you need is to be influenced by your power requirement, but typically, the higher the capacity, the better. Capacity is rated amp hours, but must be converted to watt hours to get the relative amount of energy it can store.

There is a mathematical formula used to covert amp hours to watts hours. All you have to do is multiple the capacity, rated in amp hours, with the battery voltage. For example, if a 10 volt battery's capacity is 15 amp hours, you multiply 15 by 10 to get the power in watt hours

Power = Battery Capacity X Voltage of the Battery

Power = 15 x 10

Power = 150 watt hours

This implies that the 10 volt battery, when fully charged, can supply 150 watts power for sixty minutes. Breaking it down further, the battery can supply 75 watts over a period of two hours and 10 watts for 15 hours. In essence, as you consume more power, the battery discharges faster. 

2. Energy Used by Appliances over a Given Time

Another thing you need to calculate is the energy consumption of appliances in that space where the solar system is to be installed. This is essential to determine the energy level the solar system is required to produce per time given. For every electrical appliance, consider the power in watts consumed over an hour to get the value in watt hours.

Power consumption for a given time = Power of appliance x Duration of use

To make it easier to understand, let's say you have an air conditioner rated at 30 watts. The energy consumption is determined by multiplying 30 by the number of hours for which the AC is used. If you use the AC for 4 hours in a day, the total power consumption will be:

AC’s power consumption = 30 x 5

AC's power consumption over time = 150 WH

In a similar manner, compute the power consumption of all other appliances and sum them all up to get an approximate power consumption of your home or office's electrical grid.

3. The Amount of Energy the Solar Panel Can Generate Over Time

Due to the intermittent nature of solar power, you have to consider the amount of energy a solar panel can produce relative to the amount of energy the batteries can store. Solar panels' power generating capacity is also rated in watts. To get the energy quantity a solar panel produces for the battery, the power generation should be multiplied by the number of hours the panel will be in direct sunlight. 

Energy generated = Solar panel rating x Exposure duration

If your solar panel has a 15 watts rating, in direct sunlight for 4 hours, will generate 60 WH to charge the battery. However, the energy generated by a solar panel is influenced by a number of factors, so it can be quite hard to predict the exact energy level generated by a solar panel over a given time. All other things being equal, an approximate value can always be calculated.

4. How Many Watts to Charge a Battery?

To fully charge your deep cycle batteries, you need to get a suitable solar panel that can generate sufficient energy levels to fill the batteries is a reasonable length of time. The answer to the question "how watt solar panel is required?" is ambiguous, as several factors like weather condition and panel placement will also affect the level of energy produced.

When you consider those factors, you should be able to establish the average duration for which the sun shines in your location. With that information and the amount of energy the battery can store, you should able to predict the range of solar panel wattage that will charge your battery.

Do You Need an Inverter?

Many people wonder if inverters are necessary for solar electric systems. Yes, they are necessary for renewable energy systems. The rechargeable batteries used in solar systems receive and release the power in the direct current form. The typical electric grids produce electricity in alternating current form, and as such, it is more practical for long-distance transmissions.

Inverters convert direct current to alternating current in solar systems for domestic use. It is something like a power adapter. In addition to converting the form of the current, it also changes the voltage. You should know that it is possible to use the direct current for the batteries, but the best form of current for typical household appliances is the alternating current.

While current moves in a single direction, alternating current changes direction many times in a second. However, it would be best if you never compromised on inverter quality, as a low-quality inverter will negatively affect your solar system's output, regardless of the quality of output from the battery.


Establishing the exact solar wattage to charge a deep cycle battery is not a straightforward process. Nonetheless, you can determine a suitable watt range that will charge your batteries fully in a given period. The process is typically easier with the input of a professional. Regardless of the cost effect of setting up a stand-alone solar power grid, the long term cost effect is cheaper than power from central electric grids. I hope you now understand how to calculate the requirements when planning a stand-alone solar power system. If you found the information helpful, do well to share with other people who may also find it helpful. If you have any thoughts you would like to share, please do so in the comment section below.

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