How to Calculate Solar Panel Battery and Inverter?

how to calculate solar panel battery and inverter

The reason that solar installation in your home isn't doing all the amazing things you expect it to do is that you haven't estimated the exact battery inverter as well as solar panels that will supply all the power you need.

This estimation requires some inevitable calculation. This is because for the better calculation you will need to combine all the necessary devices, most appropriately, to achieve the optimal result. Now, let's break this down a little further. If you own a house and you have estimated your appliance load to be 100Watts, and you need this for ten hours daily, to achieve this, you need the best combination of solar panels and battery to be able to achieve this.

Although, calculating solar panel battery and inverter isn’t such a difficult task, but it could be a demanding one. However, we promise to break it down the best way we possibly can. Thus, how to calculate solar panel battery and inverter?

1. Understand Your Load Wattage?

Without calculating the load wattage you need for a defined space, there is no way you will get the appropriate battery that measures up to that load wattage. It is fine if you cannot calculate the load wattage of your home or any other defined space. You are not an expert but then again, you can estimate what you think your load wattage is.

The best way you can do this is simply by looking at the wattage of most of the appliances you want your solar power installation to power. Now, let us assume that at the end of summing up the wattage of the major appliances around your home or anywhere else you want to have the installation, you come about a total wattage of 150, and you will love to have your solar running this wattage for a total of ten hours daily, the next thing to do is a simple multiplication.

Hence, you multiply 150watts by 10 hours, and you will have an estimated 1500 wat hours. This 1500 watt-hour then becomes the absolute power you will need your solar panels to store in an inverter for you. what this means is that you will be needing a battery with than estimated load wattage. Pretty easy to calculate isn't it? But that is not all.

2. Estimate the Solar Panel Dimension

The solar panel is the next thing you have to consider after you are certain about the wattage hour you need to run for your space, which is the solar panel dimension. Since you are relying on sunlight, to help you save enough usable energy, then you need a solar panel that is wide enough to handle the transmission job.

It is the solar panel that transmits enough usable energy from the sun into the inverter. Thus the wattage capacity of your solar panel must measure up and correspond with the consumable wattage-hour you have already estimated. We do not intend for any of this to be confusing, so let’s break it down.

Using our analogy from above, let’s assume you estimated wattage-hour is 1500, the next question will be what is the most appropriate solar panel for this wattage hour? To get an answer, you need to determine the number of sunlight your area experience per day. In a typical summer season, you may experience up to ten hours of direct sunlight daily.

Since you already multiply your estimated load wattage of 150 by ten hours, which is the number of times you want to run it for, all you have to do to get the most appropriate solar panel wattage is dividing the estimated wattage-hour by the number of expected direct sunlight. Hence, 1500 wattage-hour divided by ten hours of direct sunlight will give 150watts. Hence, you need a 150watt solar panel in an area that experiences up to ten hours of direct sunlight to cater for an estimated 1500 wattage hour of the load.

Flowing from the above analogy, it becomes obvious that when the number of hours for direct sunlight is reduced, perhaps because of change in season or clime, two implications may arise. The first is that you need a longer time to get your solar system to deliver the estimated wattage-hour. The second is you may need to get solar panels with higher watts.

Hence, let’s say the expected ten hours of direct sunlight is reduced to five, just because it is winter or you say in areas with lower sunlight, you may then divide 1500 wattage hour by five hours of direct sunlight. This means you need a 300watt solar panel to meet that load wattage hour. It’s been pretty simple so far right? Well, that isn’t still all.

3. Consider the Right Battery Ampere Hour

Your solar panel will surely tap some solar energy, and it needs a battery reservoir to store away this energy. However, your battery must be of that capacity that can save the maximum level of power a solar panel can transmit into it. Thus, you cannot have a 50AH battery and expect that it will conveniently cater for a 1500 wattage hour, just like our analogy.

The commonest batteries are the 12V and 24V batteries. However, these batteries come in different amp hours. Let's assume you have an estimated load of 1500 wattage hour, and you have secured a 12V battery, what amp-hour capacity should your battery then possess?

All you have to do is to divide that 1500 wattage hour by 12V to see if the battery has the average amp hours needed for that kind of load. The division will reveal that although it is okay for your battery to be 12V, it will need at least 125 amp-hour to be able to carry the 1500 wattage hour.

This isn't just all. You also need to add a tolerance percentage of at least twenty percent, if you want a battery that stays at its optimal game at all times. With a twenty percent added tolerance, you will then need a 12V battery with 150Ah capacity to carry your load requirement using 1500 wattage hour. As far as inverters are concerned, just look for the inverter that can carry 150Watts load conveniently. You may also choose to add a certain percentage of tolerance to the wattage of your inverter for a more reliable power supply.

Now, let's try to bring all our calculations together to make a meaningful sense. If you are looking at installing a solar panel system in your home where you need an average of 150 watts for at least ten hours, then you need at between 150-300watt solar panel. Then you need at least a 12V battery with a minimum of 125Ah capacity. In case you are wondering how we arrived at this figure, reading through the well-explained calculation above will help.


From the above explanation, you will realize that calculating the appropriate power capacity for your solar panel, battery, and inverter isn't as difficult as the professionals make it to appear. With a basic understanding of how all the devices, needed for powerful solar power installation, work together is sufficient. We hope you now know how to calculate solar panel battery and inverter, and how to make all these devices work for your optimal benefit?

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