Calculate Solar Panel Battery & Inverter? [Solved]

When designing a solar panel, some frequently asked questions are how many solar panels are required for my place?

How to connect solar panels to battery bank charge? How big should be batteries for solar panels?

How many batteries needed for the solar panel? And the most common one how to calculate solar panel battery and inverter.

These questions are mostly asked by the people who are installing the solar panel charging system for the first time or don’t have access to the off-grid charge controller.

If you are new to this, this lengthy guide is going to be extremely beneficial for you, and by the end, you will know all about how to calculate solar panel battery backup and inverter size and solar battery sizing along with all other necessary info about the subject matter.

After deciding the battery’s type, the next vital thing is to conclude the system’s size.

It can be a bit technical, but we have tried our best to keep it as simple as we can. Sizing your solar panel with battery and inverter required a lot of calculations; therefore, it is vital to be vigilant from the beginning.

Inverter Size

First, start by determining the inverter’s size and find out the actual consumption or max watts of your house. To do this, sum up the watts of all the electrical appliances which you use.

Sum up everything, appliances like fans, lights, Television, cooker, and laptops.

The total sum will determine the invert’s size as per your home requirements.

Besides, remember that some appliances use rated power while starting. So, take into account that additional usage when calculating. Let’s demonstrate this by an example:


Suppose there are three lights with 60 watts each and a microwave that works at 300 watts. To determine the inverter’s size, follow this method: 3 x 60 + 300 = 480 watts

Daily power consumption – Calculations:

After determining the inverter size, the next step is to calculate your home’s daily power consumption.

Remember that it should be in hours. To calculate this, note the approx. duration or number of hours a single device consumes daily in your home.

After determining the hours used by the electric appliances, multiply the device’s wattage by the hours. This will calculate the energy used in watt-hours per day. Add the watt-hour figures to know the total consumption of your house.

Usually, the figures are low as there are efficiency losses. To conclude the actual values with the system’s efficiency losses, it is advised to multiply the value by 1.5. This will give you some extra tolerance, which is always handy and also helps if the temperature rises. Let’s check this by an example:


If you use a light bulb in your house 6 hours a day and a laptop for 3 hours a day. The daily consumption will be: 120 x 6 + 300 x 3 = 1620 1620 x 1.5 = 2,070 watts-hours

Autonomy Days

You can also determine the autonomy days easily. It is an energy or power you want in a solar battery bank (as per the number of days). Preferably, this should be between two to about five.

The capacity of Your Battery Bank – Solar battery bank calculator

After implementing all the steps mentioned above, it’s time for solar battery calculations. To calculate the minimum battery capacity (ΔH), multiply the watt-hours per day from the value of Autonomy Days.

This will show that half of the battery is discharged. Hence, you can multiply the value by two and then convert the value from kWh to amps hours (ΔH). To convert, divide using the battery’s voltage.


Below is the simple solar panel battery charger calculator. Suppose you want your solar panel battery to work for three days without recharging, and your consumption is 1.8kwh per day. Then the battery’s capacity will be: 1.8x 3 x 2 = 10.8kwh

The capacity battery bank for the solar panel – How to calculate the amps?

To convert this to ΔH, divide the value with your inverter’s voltage. This will be under 12, 24, and 48. So, if you plan to go for a 48V solar inverter, the minimum battery (ΔH) capacity will be calculated like this: 10 800/48 = 225ΔH This is it! But remember that these solar battery calculations are not for all wiring setups, only applicable to standard wirings.

Charge Controllers – Never overcharge the battery!

The next step in sizing your solar panel system and in calculating solar panel battery and inverter is to know the charge controller’s sizing. Charged controllers or battery charge controllers are required to control the power coming into the solar battery from the panels.

They are essential for any off-grid system and also prevent the battery cells from getting overcharged. Usually, you will find two types of battery charge controllers. These are called PWM and MPPT charged controllers.


Once you know how to calculate the solar panel battery and inverter’s size, then, it is time to determine the type of charge controller and controller’s sizing.

It is simple, and you can use the below-mentioned formula for this purpose: Power = Voltage x Current Next, divide the battery’s voltage by the solar panel’s power. Let me elaborate this by an example:


If your solar panel generates one kW and you have a battery bank of 24v. The controller’s size will be: 1000/24 = 41.67amps For added tolerance and safe side, you can multiply the value by 1.25: 41.67 x 1.25 = 52.09amps By looking at the example mention above, it is evident that you need at least a 52amp solar charge controller inverter. We hope that this post will help you out, and now you know how to calculate solar panel battery and Inverter.

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