The size of the inverter should be selected according to the load being used. The following steps should be considered;
Step 1: Calculate the total wattage of load you will desire to run on the system. For eg., for running fan, bulb, computer etc .(Suppose we calculate 840 Watt).
step 2: The total load should be divided by 0.7 (Power factor for low capacity systems) to convert watts into VA. Then we get;
840 Watts = 1200 VA 0.7
Step 3: -Finally by getting VA, add 10% - 20% extra to the VA and the final system is selected. We need to add this extra load to keep our system on safer side.
Step 4: -- If the fixed rating system is not available, then always choose the higher capacity of the size calculated. Thus Su-vastika makes 1400 VA system and so 1400 VA system is suitable for this load.