How to size an inverter

Power Supply | Appliance wattage advisor | Inverter buying guide

What to consider before you buy an inverter


Inverter buying guide


Inverters are used to store electrical energy in batteries during periods of power supply. This energy stored is released during periods of outage. The capacity of the inverter and battery, as well as the number of batteries determine the quantum of energy stored and hence also the quantum of energy released during periods of outage. Therefore the higher the capacity of the inverter-battery system, the higher the load capacity.

Sizing an Inverter

The higher your load requirement, the higher the capacity of the inverter-battery system you should opt for. You are encouraged to use the I-WIN energy estimator to determine your energy requirement that will hence enable you size the inverter-battery capacity you need. Customers should be aware that the use of inverter system mimics a phantom load during periods of power supply availability in the sense that the energy used in charging the batteries is recorded by the energy meter as additional load. So the use of inverters without solar panels will lead to higher electricity bills.

It is generally advised to use inverters with solar panels for two reasons:

  • the energy used to charge the batteries do not reflect on the meter because it is directly from the sun
  • efficiency of charging the battery is higher with solar panels which leads to longer battery life. It has been observed that batteries tend to last longer when the charging energy comes from solar panels than from the mains.

For more information on inverters and how they work, read Power Inverters: all you need to know and Inverters, solar panels and energy storage: facts you may not know).

For cost purposes, you may need to wire your facilities such that only critical equipment is powered by the inverter. this way you may choose to purchase an inverter with lower capacity than your actual energy requirement.


Make sure you buy the battery from an accredited dealer of the battery manufacturer who can offer you valid warranty. Same goes for the inverter panel itself.

Always remember to check for warranty. The duration of the warranty determines the confidence the manufacturer has in the product. Therefore the longer the warranty, the more confident the manufacturer is that the product is durable. Never buy an appliance with no warranty! Finally, you should buy from an authorized dealer to ensure that the warranty is valid.


There are many inverter brands in the market. Always check for the SONCAP and the warranty (as said above). Finally you can tell us your experience with your appliance, or as your questions, in the comments section below.

Use our generator sizing tool to size your inverter now!

Calculate the total wattage of your appliances to determine the most suitable inverter for your household needs

Newsletter signup

Subscribe to stay up to date with the latest buying tips on Checkit

Please wait...

Thank you for signing up!

Please share: