Calculation for your Home Inverter (Approximation)
Surely, if you want to buy an inverter, it is very important to calculate the capacity of Inverter that will outfit your requirement. The power consumption of home appliances like tube light, fan, TV, laptop, CFL, etc. shown in table as below, for example
Tube light - 60W
Fan - 70W
Television - 120W
Laptop - 100W
CFL - 25W
Modem - 50W
To understand as what capacity inverter you need, I will let you do that in 3 simple steps.
1. CALCULATION FOR POWER TO BE NEEDED
Now I will explain you how to use above table to calculate the right capacity Inverter for your need. Let's say you need Inverter to run 2 Tube lights, 3 Fans, 1TV, 1 Laptop and 2 CFL.
As per the table above, you will need a total power of 600W (=2X60 + 3X70 + 1X120 + 1X100 + 2X25) to support all of your equipment at the same time.
Your Total Power Need = 600W
2. CALCULATION OF REQUIRED INVERTER CAPACITY
Now that you know how much power is required, it's easy to get the VA rating of inverter. In ideal condition, the VA rating would have been same as the power need i.e. 600VA. But in practical conditions, the power factor of Inverter is less than 1 hence power supplied by 600VA Inverter won't be 600W but lesser than that. Assuming power factor of Inverter to be 0.7, following are the details of calculation,
Required VA of Inverter X 0.7 = 600W
Required VA of Inverter = 600/0.7 = 857 VA
Now fortunately we have inverters available in the market with 900VA capacity, so such inverters will fit into my requirement.
3. CALCULATION OF INVERTER BATTERY CAPACITY
Till now, you will have clear understanding of the Inverter capacity required for your need. But the next question is that how much back up will the inverter provide and for how many hours you can run all of your equipment. And that's where battery capacity comes into picture. It's the battery which determines the back-up hours. The higher capacity battery you have, the more back-up hours you will get. So let’s get into the calculation fast.
Required power (in Watt) X Required back-up hours (in Hours) = Inverter Voltage (in Voltage) X Battery Capacity (in Ampere Hours)
Let's look for an Inverter which can give back-up of up to 2 hours, so for our case -
600W X 2Hours = 12V X Battery Capacity
Battery Capacity = (600 X 2)/12 = 100 Ampere Hours
So we need a battery of 100AH capacity, which is available in the market. So that it should be more sufficient for your need.