Inverter Battery Size Calculator-Definition and Instructions

In our homes today, it is risky not to have an inverter that helps to ensure your appliances get the right amount of power at a time. Inverters also help to power up these appliances for a couple of hours or minutes when grid power is off. The time the inverter will last when power is off will largely depend on the battery capacity of the inverter.

So before buying an inverter, it is important you establish your needs and from there you can calculate the specifications of the inverter that will be able to meet those needs. The inverter power is normally rated in KVA and its battery is rated in Watt-hours or amp-hours.

How do you calculate inverter battery size?

The battery size of the inverter is calculated based on the inverter specifications. The most important of these is the power rating of the inverter. If the power rating of the inverter is not known, it can be calculated by dividing your power needs in Kw with the power factor. This will give you the power rating of the inverter in KVA which is normally the standard rating of power for inverters.

The power required in KW can also be calculated from the total load that will be powered up by the inverter. For example, if all the appliances in your house need a maximum power of say 300W. This means to power up all these appliances with an inverter, you will need one that can supply 300w or more at a time. So, to get the power rating of such an inverter in KVA, we shall do the calculation as follows.

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Power rating in KVA=Power in KW/Power factor (PF)=0.3kw/0.8 =0.375KVA.  Please note that the standard power factor for homes is approximated to be 0.8. From this power rating, we can now compute the battery size that can power up such an inverter using the formula below

Battery capacity = rated power * desire battery time. The desired battery time is the amount of time, you would want the battery to last. For instance, if you want the inverter to power up your appliances for 2 hours, this means you need a battery with a capacity that can provide such time or more. Going back to our example, Battery capacity = 0.375(KVA) * 2(hours) = 0.75KVAh. To convert this to KWH, you will need to multiply it by the power factor

Therefore, the battery capacity kwh = 0.75*0.8=0.6kwh. If the overall voltage of the invert is known, you can also convert this value to Ah or mAh. If we consider a voltage of like 12V, then the battery capacity in Ah=0.6/12=0.05KAh=50Ah.

In summary, a system that has an overall total power rating of 300W, can be powered for two hours with an inverter rated at 0.375Kva and with a battery of 50Ah. If a few appliances are connected to the inverter, then the battery will be able to last more than two hours.

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What is an inverter battery size calculator?

For the common person, doing the calculations I have just shared above may not be desirable. Most people wouldn’t want to go through that hustle to know the size of the battery they need to power up their system. That’s why there are inverter battery size calculators to assist in doing all that work for you. All you need is it give it a few inputs and it will give you the inverter specifications you need including the size of battery needed.

The inputs the user will have to input include; the various power ratings of the appliance and the amount of time you would want the battery to power up these appliances when power is off. With these inputs, the calculator will give you the battery capacity you need and the power rating of the inverter that can be powered by such a battery.

If you don’t know the power rating of your appliance, simply check at the back or the bottom of the appliance. That’s normally where the power rating of the appliance is written. All you need is to look for the figure with the watt’s units. That’s the power rating of the appliance. Please note that if you give the calculator wrong values, it will give you wrong results as well that may lead to buying an inverter that may not meet your power needs.

What are the instructions of an inverter battery size calculator?

Like we have seen above, the instructions given to the inverter battery size calculator are the input parameters required. In situations where the inverter power rating is known, then you will only need to specify the amount of time you want the inverter to power up the appliances when grid power is off. With the two parameters (power rating and time), the calculator will be able to determine the battery size that will get the job done

Final thoughts

As we have seen above, the size of the battery you chose for the inverter will determine how much power you will be able to get from the inverter and how long that power will be provided before the battery drains. Another thing you need to remember is applying some margin of error. For instance, if you establish that your power requirements are 3000w, it is better you get an inverter that has a slightly higher power rating so that you don’t get issues of overloading

If you want the battery to last about 2 hours, you may need to input about 2.5 hours. Incase there’s a slight increment in the power needs of your appliance, the battery will still be able to run for the two hours you needed before. You may also want to put into consideration an increase in your power needs in future. In such a scenario, you may have to get an inverter that exceeds your current power needs by a significant margin so that when you add more appliances, it will still be able to run without any issues.