How does a solar power system work in a Brisbane home?

A solar power system turns sunlight into electricity your home can use. It sounds technical, but there are only a few parts, and each one has a simple job. This guide follows the power from the roof to your power points, then explains what you see in the app and why the numbers change from hour to hour.

Solar panels: where the power starts

Panels sit on your roof and turn daylight into direct current (DC) electricity. They have no moving parts. The more daylight that reaches them, the more power they make, so output climbs through the morning, peaks around the middle of the day and falls away in the afternoon.

Brisbane gets plenty of sun, but panels do not need heat to work. They need light. In fact, very hot panels tend to be a little less efficient than cool ones, which is one reason a bright, mild day can out-perform a scorching one.

The inverter: making the power usable

Your home runs on alternating current (AC), not the DC that panels make. The inverter sits between the two and converts one into the other. It also watches the system all the time, and it is the part that talks to your app over your home internet.

If something is wrong, the inverter is usually where you will see it first, through a light, a message on its display or a notice in the app.

The meter and the grid: what happens to the power

Once the inverter has made AC power, your home uses it first. Appliances, lights, the air conditioner and the fridge all draw from your solar before they draw from anything else.

If your panels make more than the house is using, the extra can flow out to the grid. If they make less, for example in the evening, the shortfall is topped up from the grid automatically. You never have to switch anything over.

Your meter keeps count in both directions: what you bring in from the grid and what you send back out. Your electricity retailer uses those readings on your bill. In south-east Queensland the local network is run by Energex, and your system has to be connected to it in line with the network’s requirements. Your installer takes care of that process.

A battery: optional, and it changes the picture

You do not need a battery to have solar. A battery simply stores spare solar power so you can use it later, such as in the evening, instead of sending it all out to the grid.

With a battery in the system, the usual order is: your home uses the solar first, spare power charges the battery, and anything left over goes to the grid. When the sun goes down, the battery supplies the house before the grid does.

What you see in the app

Most systems come with an app or web page that shows what is happening in real time. The names differ between brands, but the main numbers are usually these:

• Solar production: how much power the panels are making right now.
• Home usage: how much power the house is using right now.
• Grid import and export: power coming in from the grid, or going out to it.
• Battery level: if you have a battery, how full it is and whether it is charging or discharging.

Many apps also show daily and monthly totals, which are handy for spotting changes over time.

Why your output changes

It is normal for the numbers to move around. These are the usual reasons.

Time of day and season

Output follows the sun. Days are shorter in winter and the sun sits lower in the sky, so a system will usually make less in winter than in summer.

Cloud and weather

Panels still work under cloud, just at a lower level. A storm front passing over can make the graph dip and recover quickly.

Shade, dirt and temperature

Shade from a tree, a neighbour’s roof or even a television antenna can reduce the output of the panels it falls on. A build-up of dust or leaves can also cut production. As above, very hot panels are slightly less efficient.