1. Home
  2. What Size Solar Inverter Do I Need? 5kW, 8kW or 12kW Guide

What Size Solar Inverter Do I Need? 5kW, 8kW or 12kW Guide

The right inverter size depends on what you run at the same time, not on the size of your house. This guide gives you a quick way to work it out and shows which inverters we stock at each size. The Sun Pays has supplied solar equipment since 2007 and sells from Rayton, Pretoria.

Want the longer South African home version with worked examples? Read What Size Inverter Do I Need? A South African Home Guide. Questions about sizing or the calculator? See the solar calculator FAQ.

Step 1: List what runs at the same time

Write down every appliance that could be on together, with its power in watts (on the label or manual). Typical examples, as a rough guide: fridge 100 to 200W, lights and TV a few hundred watts, microwave 1,000 to 1,500W, kettle about 2,000W, air-conditioner 1,000 to 2,500W, electric geyser 3,000 to 4,000W, pool or borehole pumps 500 to 2,000W or more. Check your own appliances, because ratings vary.

Step 2: Add headroom

Add 25 to 30% on top of the total for motor start-up surges. Pumps, fridges and air-conditioners draw several times their running power for a moment when they start.

Step 3: Match the total to a size

  • About 3 to 5kW: lights, TV, Wi-Fi, fridge and a few small appliances. No big heaters.
  • About 5 to 8kW: add a microwave, kettle, washing machine or a pump, with some appliances on together.
  • About 8 to 12kW: large homes, farms and small businesses with several heavy loads, air-conditioning or pumps at the same time.

These are guides, not rules. Send us your appliance list and our technical team will recommend a size, or try the sizing calculator.

Inverters we stock

See all options in our inverter collection. Reading about 12kW specifically? See How to choose a 12kW inverter.

Do not forget the batteries

A bigger inverter can pull a lot of current from the battery bank. At full load a 12kW inverter draws roughly 250A from a 48V bank, so battery capacity and discharge rating must match. Browse our lithium batteries.

Frequently asked questions

Is it better to buy a bigger inverter than I need?

A little headroom is sensible. Far too large an inverter costs more and still needs batteries and panels to match. If you expect to grow, pick an inverter that can be connected in parallel.

What does 48V mean?

It is the battery system voltage. Larger inverters use 48V because it carries the same power at lower current than 12V or 24V. Our 51.2V lithium batteries suit 48V inverters.

Single-phase or three-phase?

Match your supply. Most homes are single-phase. If you have a three-phase supply and need to power three-phase equipment, ask our technical team before ordering.