The power requirement at your home can be different from you neighbour’s home. So instead of blindly installing the same inverter for your home, understand how to choose the right inverter/UPS and batteries, the hours of power cut in your area, the hours of back-up you require and the number how appliances requiring the back-up.
Inverter v/s UPS
The fundamental functions of the inverter and the UPS are the same. However, when there is a power cut, there is a need to switch over from the main line to the battery power. The inverter takes around 100 milliseconds whereas the UPS would do the switch in 3 to 5 milliseconds. Therefore, you get almost uninterrupted power supply in a UPS.
Specific appliances like your desktop PC can switch off even if there is no power supply for a few milliseconds. Hence, you have to use the UPS instead of the inverter to ensure that the PC does not switch off during a power cut.
Now coming to the advantage of having an online UPS over offline UPS, Online UPS supplies power continuously from the battery even when the main line is on, recharging the batteries simultaneously. Therefore, there is no loss of power even for a single millisecond. On the other hand, the offline UPS uses the battery power only when there is a power cut. At other times, it uses the main power line.
All the inverters and UPS’ available in the market come with a rating ranging from 300 VA to 5,000 KVA. The best practice is to choose a UPS with a power rating that is 1.2x the total load you need it to support.
How to calculate the VA rating of an inverter?
The table below gives you an idea of the electricity consumption (in Watts) of the common electrical appliances you may want to use during power cuts.
High power consuming appliances like AC, induction cookers (1000W), iron (750 W), water heaters, water motor pumps (750 W), and washing machine (500W) are usually not connected to the inverters. During power failures you may not use all these appliances at the same time.
For example, if you wish to use one CFL bulb, one fan, one tube light, and one LCD TV during a power failure situation. These appliances will consume approximately 275 to 300 watts. Say you need this backup to be available for 4 hours. Hence, you will need to store 1.1 to 1.2 kWh of electricity. The thumb rule is that you divide the total required load in watts by 0.8 to arrive at the VA value.
In our case, 343 VA to 375 VA would be the maximum inverter load. Remember to calculate your exact requirements and add 25% more to the value to choose an inverter with a slightly higher capacity (VA) for better backup. So you can safely select a 400 VA inverter.
Now that you have understood the difference between UPS and inverter and how to select the ideal for your home, let’s see how to select the battery size to go with it.
| Electrical Appliance | Power Consumption |
| Television | Depending on the size: LCD TV: 50 – 150 Watts LED TV: 30 – 100 Watts |
| Electric/CFL bulbs | Depends on the Watts: 10/20/25/40/ 60/100 Watts |
| Computer | Depending on the type: 120- 600 watts LCD monitors -150 watts whereas the conventional CRT monitors consume about 250 watts, gaming ones – 500 watts |
| Fan | 60 to 70 Watts |
| Tube light | T 12/T8 tubes consume 40-32 watts whereas LED tubes consumes just 15 watts |
| Set Top Boxes | SD Set-top boxes – 8 Watts, HD Set top boxes – 18 Watts, and the HD DVR Boxes – 25 Watts |
| Mixers and grinders | 300 to 400 watts |
| Water Filter | 70 to 100 watts |
| Mobile Phone Chargers and Wi-Fi routers | 5 watts or less |
| Fridge | 100 and 300 watts. |
High power consuming appliances like AC, induction cookers (1000W), iron (750 W), water heaters, water motor pumps (750 W), and washing machine (500W) are usually not connected to the inverters. During power failures you may not use all these appliances at the same time.
For example, if you wish to use one CFL bulb, one fan, one tube light, and one LCD TV during a power failure situation. These appliances will consume approximately 275 to 300 watts. Say you need this backup to be available for 4 hours. Hence, you will need to store 1.1 to 1.2 kWh of electricity. The thumb rule is that you divide the total required load in watts by 0.8 to arrive at the VA value.
In our case, 343 VA to 375 VA would be the maximum inverter load. Remember to calculate your exact requirements and add 25% more to the value to choose an inverter with a slightly higher capacity (VA) for better backup. So you can safely select a 400 VA inverter.
Now that you have understood the difference between UPS and inverter and how to select the ideal for your home, let’s see how to select the battery size to go with it.
How to choose the battery size?
There are whole lot of batteries available in every brand. The right choice of battery for the right application is of utmost importance to improve the reliability of the system. Here is a simple formula to know which battery size suits your need:
