How Many Watt Solar Panel To Charge Deep Cycle Battery

How many watt do we need for your battery?

Off-grid living is slowly but surely gaining its popularity nowadays; it is one of the new trends of today that gets a lot of people interested. It is a self-sufficient lifestyle that doesn’t rely on public utilities and makes use of what mother nature can provide.

Going off-grid means going solar, where you are going to harvest the most renewable energy available and converting it to electricity to power your home its electrical components. It’s a more eco-friendly way of supporting all the comforts of home with a great money saving potential in the long run.

However, going solar also means that you need to use highly efficient batteries to store the harvested energy. Using the right one is crucial to have a stable and reliable power source for your home.

Some off-grid experts use reconditioned forklift batteries to save money and get massive storage capacities. But if you have an idea of how many watts are needed for a solar panel to charge a deep cycle battery, you are going to have a very efficient and reliable off-grid solar panel power system installed!

Here you are going to learn how to calculate your solar power requirements and everything you have to know about hooking up a highly reliable and sustainable solar panel system. So sit tight and be prepared to enlighten yourself on how to go solar!

Guide To Calculating Solar Power Requirements

To compute or calculate for your solar power requirements, there are three significant aspects that you have to consider to get an accurate result. Thinking about these important aspects is the key to install a solar panel power system that will be capable of running your entire home without any hiccups or issues.

So let’s begin calculating your solar power requirements by going through these aspects one by one!

The Amount Of Energy The Battery Can Store

The battery’s maximum energy storage capacity is one of the main things that you have to consider if you want to have an adequate and reliable power system. The more energy you can store the more dependable your system will be.

​Your battery capacity is measured in terms of Amp Hours which has to be converted into Watt Hours. You can do this by simply multiplying the amp hours of your battery with its voltage. To make easier, take note of the mathematical formula below.

Power in Watt Hours = Battery Capacity (AH) X Voltage of the Battery

So let’s say you have a 12-Volt battery with a capacity of 20 Amp Hours (AH). You can convert its capacity measured in AH to Watt Hours by simply doing the mathematical equation below.

Power (Watt Hours) = Battery Capacity (AH) X Voltage (12V)

Power in Watt Hours = 20 X 12

Power in Watt Hours = 240

Power = 240 WH

The equation above simply means that your 12-Volt battery will be able to deliver 240 Watts of power for an hour, 120 Watts for two hours. It may also mean that your battery can provide 2 Watts of power for 120 hours. It depends on how much power you are using, the more power you use, the faster your battery will discharge.

You also have to keep in mind that it’s not possible to take all the power stored in your battery. Once the voltage drops and it’s below the voltage requirement of an electrical component, the component will stop running.

Energy Consumption Of Devices Or Appliances Over Time

​To calculate your power requirements to make sure that your solar panel system is capable of running your home electrical grid. You also have to consider how much power your appliances or devices will consume over a period of time.

Considering this aspect will give you an idea of how much power your system should deliver to run your home 24/7. Power is measured in Watts, and you have to get the value of power consumption over a period of time which is measured in WH.

​To calculate for the power of your home devices will consume over time you have to multiply power consumption (Watts) by the number of hours the devices will be used.

Power Consumption Over Time (WH) = Power (Watts) X Hours of Use (Hr)

For a better picture, to compute for the power consumption of a TV that uses 20 Watts of power used for 5 hours a day. It will be mathematically represented on the equation indicated below.

TV’s WH = Power Requirement (20 Watts) X Hours to be Used (5 Hours)

TV’s WH = 20 X 5

The TV’s WH = 100 WH

This means that if you are going to use a TV with 20 Watts power requirement for 5 hours a day, its total power consumption over time will be 100 WH. To calculate your total home power consumption, you can do this computation for every single appliance or device at home then sum up all the results you will get. This will lead to an accurate value of how much power or energy your entire home electrical grid will consume.

The Amount Of Energy The Solar Panel Can Generate Over Time

Finally, calculating your solar power requirements will also require you to consider how much energy your solar panels can generate over a certain period of time. This is going to be another important factor to consider since solar panels will only have the entire daytime to harvest the sun’s solar energy.

A solar panel’s rating for generating power is also measured in Watts and to calculate the energy it delivers to the battery. You will have to multiply the power generation rating of the solar panel by the number of hours it will be exposed to sunlight. This is represented on this mathematical equation.

Energy Generated Over Time = Solar Panel Power Rating (Watts) X Exposure Time (Hr)

So, if you have a solar panel that with a 10 Watts power rating and it is exposed to sunlight for at least 6 hours. You can get the amount of energy it will provide the battery by multiplying 10 Watts by 6 hours which will give you 60 WH. This means that on that scenario the solar panel delivered 60 Watts of power to charge the battery.

Considering these three main factors before installing or setting up a solar panel power grid will help you make sure that you will have a highly reliable system. An off-grid power system that has all the ideal specifications to supply the power you need to run your home on a daily basis.

How Many Watts Is Needed To Charge A Battery?

When it comes to calculating the solar power requirements of a home electrical grid, formulas are used to get accurate results. However, answering this question is not as simple as the computation above.

Unlike those computations, determining how much wattage a solar panel needs to generate to charge the battery fully will depend on several uncertain factors.

These different factors vary according to how the power grid system is set up and the uncertain exposure time of solar panels. Every set up will also have different battery capacity, voltage and solar panel specification which will make it more difficult.

In this case, what we can do is to calculate the average charging time of the battery!

First, you will have to determine the Ampere per hour rating of the solar panel by dividing its power generation rating given in watts by the voltage of the battery.

Then take the battery capacity which measured in AH and divide it by the amp rating (the result from prior computation) of the solar panel and then adding 10% of the Charging Time to it. The additional 10% is to make sure that the battery is fully-charged.

Ave. Charge Time = (Battery Capacity (AH) / Ampere Rating of Solar Panel) + 10% of CT

WHERE: Ampere per Hour Rating of Solar Panel = Solar Panel Rating (Watts) / Battery Voltage

and CT = Battery Capacity / Ampere Rating of Solar Panel 

Let’s say you want to compute for the average charging time of a system with a 12V battery with 50 AH capacity and a 15 Watts solar panel. The first thing you have to do it to compute for the ampere rating of the solar panel by following the equation below.

Ampere per Hour Rating = 15 Watts / 12 Volts

Ampere Rating = 1.25 amps

Then, divide the battery capacity which is 50 AH by the Ampere per hour rating of the solar panel which is 1.25 amps which will be the Charging Time. Then add 10% of the Charging Time.

Ave. Charging Time = (50 AH / 1.25 amps) + 10% of CT

Ave. Charging Time = 40 Hours + 10% of 40

Ave. Charging Time = 44 Hours


Identifying how many Watts is needed for a solar panel to charge a deep cycle battery is a difficult task due to the dynamic factors involved. However, the more important thing is to determine the power requirements of your home to determine the best suitable components for your solar system.

To make sure that you will install a reliable and efficient stand-alone power grid. You can save money and reduce the cost of installation or set up by using reconditioned batteries which are cheaper.