How to choose the right inverter and batteries for your needs


Load-shedding is here to stay for the foreseeable future, and it’s definitely not going to ease up in winter. 

If you haven’t already made some sort of “off-gird” back-up plan for when the lights go out, now is the time to get cracking, as winter is going to be mighty cold if the heating stops working. 

An increasingly popular solution is to invest in an inverter and battery system. An inverter is a back-up power-generating device that draws power from a battery. The battery is charged through your household electricity supply when available and stores this power to be used during load-shedding by the inverter, which provides your home with an uninterrupted electricity supply.

The challenge, however, is choosing the right inverter and battery for your needs. There is no one size fits all solution, as the needs of every household or office are different. We asked Brights Hardware to assist us with an easy, 4-step guide to choosing the right inverter and battery system to fit your power needs.

Step 1: How much power do you need?

Make a list of the devices and appliances you want to run during a power outage. This probably includes the TV, Wi-Fi, a few lights, and maybe the fridge? 

Then add up the wattage of all these items to work out your total needs per hour. An average Wi-Fi modem uses 15W, a TV is approximately 150W, a fridge uses 500W and five 10W LED lightbulbs use 50W – this totals about 715W. In this case, a minimum 1000W inverter would be required.

Step 2: Chose an inverter

Now, the next step is to buy an inverter that can supply the amount of power (measured in Volt Ampere or Watts) suitable for your needs. The inverter’s rating must be at least 25% greater than the total amount of power you need to run all your devices and appliances at once. Here are the four types of inverters to choose from:

  1. Off-grid: These have no connection to Eskom, but also no ability to put energy back into the grid. They need sufficient batteries for energy storage,
  2. On-grid: These inverters are connected to the Eskom grid, and they will also put excess power back into the Eskom grid when available. They do not need storage/batteries
  3. Grid-interactive: These inverters do not have to be connected to the Eskom grid, but can be.
  4. Hybrid: These inverters combine the characteristics of grid-interactive and on-grid inverters. They require a battery storage size that is dependent on your load requirements. 


Step 3: Check the wiring before you buy

Before picking an inverter, make sure your home wiring is compatible with the inverter you are buying. Ask a technician to check this for you before buying. 


Step 4: Get the right battery

Without the correct battery, your inverter system will not work properly: 

  • Ensure that your inverter batteries’ capacity matches the capacity of your inverter. Note that a battery’s capacity is the electricity it can store, and the inverter capacity is the amount of electricity it can serve at a time. 
  • Go for lithium, gel, absorbent glass matt, deep-cycle, and G/P batteries.
  • The battery capacity, which is calculated in Ampere hours, can be found based on the backup time needed for all your appliances. There is a simple calculation that will help you pick the perfect battery for your needs: Multiply the wattage you need by the time you need it for. For example, if you need to run devices and appliances that total 265W (your calculations) multiplied by 4,5 hours (the amount of time you need it for) you come out with a total of 1192,5Wh – this is your energy needs in Watt hours.
  • If you are running a PC, a UPS is better suited, as an inverter takes one microsecond to fall over to the backup power, and this delay in switching may harm the system.