inverter-for-home

Size matters! What size inverter do I need to run a house?

Last Updated: January 18, 2024By

Loadshedding sucks but an inverter for your home can help ease the pain. So you head down to Makro, Leroy Merlin or your local solar shop, credit card in hand, ready to buy. But what should you buy? How do you know what size inverter you need before you buy an inverter? You ask yourself the question asked by thousands each day: “What size inverter do i need to run a house?”.

Panic ensues.

Relax, friend, I’ve got your back. Let’s take a non-technical walk down the inverter aisle and stroll through the options in a friendly, easy-to-understand way.

First, let’s look at some of the common questions people ask.

Common questions about home inverters

  • Can I run a fridge or freezer with an inverter?
  • Can I run my oven with an inverter?
  • Can I run the geysers from an inverter?
  • Can I run my heater from an inverter?
  • What appliances can an inverter run?
  • How many inverters do I need?

Asseblief mense, nee…don’t try and run anything that generates heat from a small inverter. Heaters, ovens, geysers are all better suited to other forms of energy like gas or thermal solar. Anything that requires heat will QUICKLY suck your battery dry.

Factors to determine the size of the inverter you need for your house

I said it wasn’t going to get technical, so here’s me keeping to that promise.

Here’s what you need to think about when you choose an inverter for your home:

  • How big is your house? Do you have a 16 bedroom palace on the cliff path at Hermanus or do you own a 3 bedroom house in Linden, or a bachelor apartment in Sea Point? Or something in between?
  • How many appliances do you want to run? Lights only? Lights plus WIFI and TV? Lights, WIFI, TV, fridge, pool pump, washing machine, air fryer? See how it adds up quickly?
  • What are the power requirements of the lights and appliances you want to run?

Use an Inverter Size Calculator

It starts with knowing the power requirements of the appliances you want to run. You can use an online calculator to figure this out. This will then give you an approximate idea of the size of the inverter you need.

Here’s a helpful calculator from Inpower.

What is asked with this calculator?

  • How many 10 Watt LED light bulbs do you have?
  • How many 116 Watt TVs do you have?
  • How many 450 Watt desktop computers do you have?
  • How many 220 Watt fridges do you have?
  • How many 440 Watt fridges do you have?
  • How many 100 Watt laptop computers do you have?
  • How many 800 Watt office equipment items e.g. printers do you have?
  • How many 7 Watt phone chargers do you have
  • How many 10 Watt WIFI routers do you have?

The calculator also asks how many hours (from 2 to 4) you would like to power your appliances.

As you can see, the above is very much geared towards your ESSENTIAL appliances that you will use for work or school (or to keep your food edible) during loadshedding hours.

If you want something more extensive you should chat to an expert solar installer or electrician.

What’s interesting about the above is that you can clearly see that certain items require a lot more electricity than others. You will become very aware of your electricity usage once you start generating or storing your own power.

What size inverter do I need to run a fridge?

First of all, make sure you know what the power consumption of your specific fridge is. You can check the fridge manual, search for the model online or there might be a sticker on the fridge with this information on it.

If the power is given in Amps, you can figure out the Watts by multiplying it by the voltage (230 Volts in South Africa).

e.g. a typical Samsung fridge/freezer combo you can buy at Game for about R13,000 has a tiny sticker on the inside of the fridge that says:

Rated input: 120 Watts

Rated current: 1.5 Amps.

Multiply the Amps by 230 Volts = 345 Watts operating power consumption

You also need to account for the fact that the fridge will need a starting surge of power can can be 2 or 3 times higher than the operating power consumption = 3 x 345 Watts = 1,035 Watts.

So you will need an inverter than can handle at least 1,035 Watts of power just for the fridge in this example, and therefore get something like 1,500 Watts at least to have some extra available.

Remember too, that you will need a PURE SINE INVERTER (instead of a modified sine inverter) since the fridge contains sensitive electronics.

In theory then you could power this example fridge with a 12 Volt car battery and a 1,500 Watt pure sine wave inverter like this one which you could order from Takealot for about R4,000 at current prices:

I don’t recommend you buy this though. What you SHOULD do is look at ALL your energy requirements (you’ve got more than just a fridge, right?) and then use an online calculator to determine your TOTAL energy needs.

Then, chat to an expert.

What size inverter do I need to run an air conditioner?

Air conditioners use a lot of power. Significant, even.

You need to understand the specific energy requirements of your air conditioning unit and then size the correct inverter and battery system to operate it.

Let’s say your AC is a 1,200 Watt unit. Expect a surge of three times that so you will need something like a 4 or 5 thousand Watts inverter to run it.

You will also need a sufficiently sized battery bank to run the AC since it requires a lot of power to run over an extended period.

What about the whole shebang?

If you want a battery and inverter system to run an average 3 bedroom house with a pool pump, AC units, TV, WIFI, fridge, dishwasher, chest freezer, microwave, computers, cellphone chargers, electric fence, gate motor and all the other typical bells and whistles you will need something like the following:

 

A very good battery system e.g. Freedom Won 10/8 LiFePO4 Battery.

Victron-Energy-Quatro-Inverter

This type of robust setup will be excellent – and if you include a solar array you will be well and truly rid of of loadshedding in your life.

We did it and here is our story about our solar installation.

But unless you are a qualified electrician who is certified to issue a Certificate of Electrical Compliance, you must NOT try and do it yourself. Electricity is dangerous and carries the risk of fire.

We recommend you get a professional to look at your specific needs and give you a quote. Once the installation is complete, insist on a Certificate of Compliance. Your insurance company will demand this too.

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About the Author: Tony Lopes

Tony is the founder and editor of CleanVolts.co.za. He has completed solar certifications and courses through Green Solar Academy. Tony's goal is to see solar panels on every roof-top in South Africa and the adoption of EVs and renewable technology across the African continent.

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