If you want to install solar power at home, you may need to replace an 80-amp main switch with a circuit breaker. In this article, we’ll explain how to identify your main switch and why it must be replaced.

Where is the electrical main switch?

Inside your meter box you’ll find meters, the main switch, fuses and circuit breakers. Switchboards are responsible for distributing electricity safely to your home.

The main switch controls the electricity supply. In other words, it supplies and disconnects power to your home.

While your switchboard is probably clearly labelled, the main switch is always the first switch in the board. More often than not, the switchboard is found inside your meter box. But, if you have safety switches located in a sub board in your garage, (or elsewhere in your home), you’ll find the main switch there.

How to identify a three-phase and single-phase home

If you have a single-phase home, your main switch will occupy one pole in the switchboard. Whereas for a three-phase home, the main switch will occupy three poles in the switchboard.

How to identify single phase and three phase home

When to replace the electrical main switch

When solar produces excess energy that’s not required for your home or battery, it’s sent to the grid. Because the electricity will flow from your home to the network, your meter box and safety switches must be safe and compliant.

When you install solar, it’s the solar installer’s responsibility to ensure the meter box and switchboard meets current electrical safety standards and distributor requirements. If it doesn’t, your solar installation will fail, and your connection won’t be finalised.

How to identify an 80-amp main switch

It’s easy to identify an 80-amp main switch. Look at the image below. You can see the “80 A” label on the main switch for this single-phase home.

In the event you decide to install solar at home, we must replace the main switch with the appropriate circuit breaker. In most cases, our electricians replace 80-amp main switches with 63-amp circuit breakers.

80-amp main switch image

Why replace the 80-amp main switch with a circuit breaker?

It’s easy to explain why you must replace an old 80-amp main switch. Let’s take a closer look with an example.

We’ll start by adding up the amperage of each switch in the switchboard pictured below. In this single-phase board, the total amperage is 178 amps. This includes everything from lighting to cooktops, air con and hot water.

Total amperage in a meter box

This calculation is important because the total amperage is the potential load. This total potential load can be a hazard when it’s pulled through the main switch, which of course goes back to the street via a cable.

So why is it a hazard? The reason being is that the cable back to the street can’t take the total load of 178 amps. Depending on the size of the cable, it’s likely only capable of taking 63 amps, or even less. So, what happens?

Well, the biggest problem with an old 80-amp main switch, is that it can’t trip. That’s because it’s a main switch and not a circuit breaker. Consequently, the total load of 178 amps can cause the cable running back to the street to melt! Therefore, we must protect the mains. That’s why we replace an old 80-amp main switch with a 63-amp circuit breaker. The circuit breaker protects the cable which runs from your home to the network.

It’s okay if your sub board is not as straight forward as the one pictured. You don’t need to know the size of the cable at your place; our electricians will determine this for you and size the main switch accordingly.


So, there you have it. Now you know why you must replace an 80-amp main switch with a circuit breaker. If you’re not sure, then get in touch. We’re here to help.

If you have an old meter box, you may well need some essential upgrades before you can install solar. Learn more about meter box upgrades here.