If you are Planning to live off grid and want to install solar panel then it is important to calculate your Solar System size Beforehand. Sizing your solar system is crucial in order to know how much your expenditure would be. But often people think it is complicated stuff and they rely on other people to calculate those.
But in this article, I am going to explain everything related to solar system sizing with real example in such a simple way that even if you are beginner, you can calculate what you are going to need. Additionally, in order to know more about solar power system, you can check Complete off grid solar system
So, without any further delay let’s start our topic.
How to Calculate Solar system Size
To calculate your solar system Size, you need to do the following steps.
- Calculate your house load for solar panels needs
- Calculate solar battery size
- Calculate solar Power wattage
- Calculate number of solar panel needs
- Calculate required current of solar panel
That seems a lot of calculation but once you understand this, it is very simple.
How to calculate your house load for solar panel needs
This is the first and important thing you have to figure out and without doing this calculation you cannot estimate the solar panel needs.
In our daily life we use different electronic appliances and you may have noticed there are voltage and wattage written on it.
First, I want you to write down those appliances name along with its wattage value.
Check the table below to follow along with me.
| Name of Appliances | Watts (W) | No of appliances | Total watts W x No | No. of Hours Runtime per day | Energy (Total watts * number of hours) |
|---|---|---|---|---|---|
| Light | 36 | 4 | 144 | 5 | 720 |
| Fan | 70 | 4 | 280 | 10 | 2800 |
| Fridge | 200 | 1 | 200 | 24 | 4800 |
| AC | 1000 | 1 | 1000 | 5 | 5000 |
| TV | 70 | 1 | 70 | 2 | 140 |
| Total | 13460 |
So Here, in the demo example, we have written down appliances name and its watt value and how many appliances of those type we have. If we multiply 2nd row with 3rd row it gives us total watts.
We wrote down the number of hours we are going to run those appliances. We multiplied total watts by number of hours we run them and it gave use total energy consumption for each of those.
So finally, we have total energy consumption of 13460wh per day
How to calculate Solar battery Size
In order to calculate solar battery size, we need the total energy consumption of our house. Since we calculated in the example that we need 13460wh of energy per day. So, our battery size should be more than that to supply that energy.
But what if the weather is bad for few days and there is not enough sunlight to charge up the battery every day. For this case let’s say we need an extra 3 days backup.
So, Solar battery size = total House energy consumption per day × 3 days (backup for bad weather)
Solar Battery Size = 13460wh × 3 = 40380wh = 40.38Kwh
So, we need 40.38Kwh of batteries for this example.
Now we know the power of our battery and we can choose to have 12v battery or 24v battery or 48v battery.
How to calculate solar panel wattage
To calculate solar panel wattage, you divide your battery wattage by number of hours of sunlight.
For example, if in my area has 5 hours of sunlight during day then I need solar panel which will recharge my battery within 5 hours.
So, to get that, Solar panel wattage = Battery Wattage / Number of hours of sunlight
In our case, our solar panel wattage will be = 40380wh / 5 = 8076wh or 8kwh (1kwh = 1000wh)
Since solar panel is not that expensive, we can roughly increase it up to 10,000wh or 10kwh
How to Calculate number of solar panel needs
In order to calculate number of solar panel needs, you have to divide the total required solar panel wattage by the number of each solar panel wattage.
So, number of solar panel needs = total solar panel wattage / each solar panel wattage
In our case we roughly made it up to 10,000wh. There are different types of solar panel in the market with different power rating like 370w, 335w,400w,360w etc.
If we use 400w.
Our required panel will be = 10,000 / 400 = 25 solar panel
Now finally we have to choose the solar charge controller for our solar panel and battery.
Since we have 10000wh of solar wattage and if we use 48v battery then,
Number of currents required to charge the battery = total wattage / voltage
Which gives us required current = 10000 / 48V = 208A
So, we can use 208A of solar charge controller to charge our battery if our battery is 48V.
Remember to have current protection in solar charge controller since the amount of current is high.
So, that is how we can size our solar power system.
The price of solar panel is not much but the most expensive part is the battery. For this high demand of power, the expense will be a lot.
So, if you have high demand of power then it is not smart choice to move off the grid and rather stick to on grid.
Of course, if you are living in an area where weather is pretty good and you don’t need extra days of backup from battery then it will be pretty budget friendly for you.
