Inverter is a device that is used as a back-up power supply, when the power from the mains provided by the energy company or board fails. We all know that battery can save electrical power for longer durations which is why it is widely used in so many gadgets. It is common thinking that battery can be used to provide back-up power. But battery power is in a different format (DC) than that used by household electrical items (AC). Hence it needs to be converted into that format (AC) that can be used by the household electrical items (AC). An inverter does exactly that. So when you shop for an inverter, actually you are shopping for an inverter and a battery.
Are there different types of inverters?
Yes, there are. Broadly saying, Digital and Sine-wave. However there are some types in between. The classification based on the voltage waveform they produce. Is it really important? Yes, for sensitive devices like computers, hi-fi equipment etc. The waveform from mains is sine-wave. Anything closer to that is desirable as all the devices are made to work on such a waveform. However battery power is DC which is linear. Digital inverters are earliest made inverters which just switches on and off the continuous flow of current to produce a square waveform.
A DC voltage waveform is given below.
When Digital inverters switch the voltage on and off, the waveform becomes like this.
Hence a digital inverter produces only an approximately equivalent waveform of the mains. So when somebody tells you that a Digital inverter is advanced as it is "Digital", beware. It is not the case with inverters.
A pure sine-wave inverter produces a sine-wave voltage, from the DC power drawn out of the battery. Hence it is superior to a digital one.
Any more classification?
The next is purely based on the amount of power they deliver, which starts from as low 300VA, which is very low. 600VA is considered a starting range. 800VA is ideal for normal usage. Beyond 800VA it becomes much costlier, which I'll tell you why in the later part of the story. To know which rating to choose, please see the table below on the power consumption of the normal household electrical equipment.
| Equipment | Power Consumption |
| TV | 100 W |
| Fans | 75 W |
| Tubelights | 40 W |
| Filament bulbs | 60 W |
| Computer | 300 W |
You can check on how much power you will need by multiplying the power for each of the items with the number of items. For e.g., if you have 4 fans then the total power requirement for the fans in your house in 4x75 W = 300 W. To simplify things, multiply the VA rating by 0.8 (lets call this as power factor). So 800 VA becomes 800x0.8 = 600 W. So based on the power requirement you can see which rating is suitable for you.
Which inverter is suitable for me?
It depends on the usage. If you can spend a little more, a sine-wave inverter will be ideal. But major cost towards buying an inverter lies in the battery you choose.
Are there different kind of batteries as well?
Yes. The basic is identical to the standard automobile battery, which requires maintenance in-terms of topping the cells with distilled water once in 3 months and does not have that much long-life. Next is the Maintenance free battery, which requires topping probably once in a year. But may run for more than 5 years. The top-end is the tubular battery, which are maintenance free and can run longer than maintenance free battery, besides having very good charge retention and hence will consume less power in charging the cells. Next comes the battery rating. An 130 Ah battery should be ideal for most cases. However you will need more than one battery if you choose an inverter that has a VA rating that is more than 800 VA.
So, now you are equipped with enough details to buy an inverter. Good luck!
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