How to Size an Inverter for Your Home

Choosing the wrong inverter size is the most common and expensive mistake South Africans make when going solar or installing backup power. This guide shows you exactly how to size an inverter correctly.

Key Takeaways

Add up the wattage of all appliances you want to run simultaneously
Add 20-25% safety margin to your total load
Inverter size must match or exceed your peak load
Battery capacity determines how long you can run, not the inverter size
Use the NavigateZA Inverter Sizing Calculator for a precise recommendation

Step 1: Calculate your load

List every appliance you want to run during load shedding and note its wattage. Add them all up to get your total load in watts. This is the minimum inverter size you need.

Fridge: 150-400W
LED lights (10 bulbs): 100-200W
TV: 100-200W
Laptop: 45-90W
Wi-Fi router: 10-20W
Total typical home: 500-1500W

Step 2: Add a safety margin

Never run an inverter at 100% capacity. Add 20-25% to your calculated load to allow for startup surges and to extend the inverter's lifespan.

Add 20-25% to your total load
Motor appliances (pumps, fridges) have high startup surge
Running at 80% capacity extends inverter life
Example: 1000W load needs a 1250-1500W inverter

Step 3: Choose the right type

There are three main types of inverters: pure sine wave (best, works with all appliances), modified sine wave (cheaper, not suitable for sensitive electronics), and hybrid (works with solar panels).

Pure sine wave: works with all appliances including motors
Modified sine wave: cheaper but can damage some appliances
Hybrid inverter: required if adding solar panels
For most homes: pure sine wave is recommended

Ready to see your own numbers?

Use the Inverter & Battery Sizing Calculator