You may be noticed that audio amplifiers, Televisions, Fluorescent lamps etc make noise on inverter power. This indicates that inverter output is not pure sine wave. Sine wave inverters are costly as compared to square wave and stepped sine wave inverters, however it is always advisable to go for a pure sine wave inverter for the safety and effective performance of your appliances.
Inverter efficiency and No load power consumption:
Efficiency of an inverter is proportional to the amount of power drawn. It varies from 90% to 50% from full load to light load. Here the notable factor is that inverter efficiency is high on maximum load. Generally an inverter is in its most efficient capacity when being used at around 1/3 to 3/4 of its full rating.
Power Consumption of inverters:
Inverters take mains power supply to charge the batteries. If the charging section of an inverter is not energy-efficient, it will waste electricity even after the battery is fully charged. This will inflate your electricity bill. It is very difficult to check this aspect in shop before purchasing an inverter. However you can test the same at your home. Switch off all appliances except the mains supply to inverter, disconnect the battery and measure the power consumption for a specific period.
Battery:
Battery is the vital part of inverter. Performance and life of an inverter greatly depends upon battery. We can see several classifications of inverter batteries. Normally high power Lead Acid batteries are used to power inverters. Lead acid batteries are classified in to different types as per application, design, technology etc.
Battery Capacity and Types of Batteries and their advantages:
Capacity of a battery is expressed in terms of Ampere Hour (Ah). It indicates the rate of current a battery can supply for a given duration. If the capacity of a battery is 100 Ah, that battery can supply 100 Ampere current for 1 Hour or 1 Ampere Current for 100 Hrs, 2 Amps Current for 50 Hrs .Capacity of inverter batteries are generally 100 Ah, 150 Ah or 180 Ah.
| Different Types of Batteries | Flat Plate Batteries | Tubular Batteries |
Maintenance Free Batteries (Sealed lead acid) |
| Batteries |  |
 |
 |
| Battery Life Span | Low (~ 3 Yrs) | High(~ 5 Yrs) | Medium (3 to 4 Yrs) |
| Maintenance | High | Medium | Low |
| Cost | Low | High | High |
| Safety | Low | Low | High |
| Efficiency | Low | High | Medium |
| Scrap Value | High | High | Low |
Difference between VA and Watts:
Often people confuse with the difference between Watts and VA ratings of inverter or other home appliances. Manufacturers use both these terms according to their requirements to confuse and mislead the consumers. Power drawn by the equipment (Power using equipment like Bulb, Fridge, Washing Machines, ACs, Stabilizers etc.) and Power generated by the equipment (Generators, Inverters, UPS etc) can be expressed in Watts or VA (Volt Ampere). In general Power generating or stabilizing equipment manufacturers use the term VA to specify their ratings and power consuming products use Watts to specify their ratings. Here comes the difference. Power in Watts is the real power drawn or supplied by equipment, this is the real value. VA is the apparent power (more theoretical) which is obtained by multiplying the Voltage and Current drawn/supplied by an equipment. We can equate the VA and Watts ratings:
Power in Watts = Power in VA- Losses
or
Power in Watts = Power in VA x Efficiency of the equipment
The ratio of Power in Watts to Power in VA is termed as Power factor. Unfortunately manufacturers often don’t specify the power factor or efficiency in their products.
Let’s see an example. You are purchasing an inverter with 650 VA power ratings. This 650 VA indicates, it can supply 650 VA power under ideal situations (means efficiency of the inverter is 100%). If we take 80% as a typical efficiency figure, the said inverter can supply 80% of 650 = 520 Watts only. Now you can understand why inverter manufacturers only publish the VA rating on their products. If an inverter or UPS is coming without mentioning power factor, you must take a safe value of 0.6 (60%) as power factor while connecting appliances.
Some point to keep in mind:
Inverter is not a Generator. Inverter has its own limitations. You can’t power and run your complete home with a normal inverter. If your power requirement is more than 3000 VA, then an inverter alone can’t cater your demands effectively. No doubt a high power inverter can run your refrigerator and air conditioners, but how long? Here your battery will not last more than few hours. Hence it is better to go for a home generator. However if you don’t want a single minute power downtime, then a power inverter – electric generator combination is a good option.
In simple words what all electrical appliances (like fan, tube lights, television, CFL etc.) you want to run at the time of power failure. The power requirement is addition of the power consumed by various electrical equipment’s.
See my next post on the topic Calculating the power consumption, inverter rating and battery rating required for Home.
