How does a grid-connected solar system work?

Posted in Solar 101

A solar system is comprised of two key components: the panels and the inverter.

The solar photovoltaic panels (also known as solar PV) are used to convert sunlight into electricity, however the electricity produced by the solar panels is DC (direct current) power and your home uses AC (alternating current) power. That’s why you have an inverter, which converts the DC power produced by the solar panels to AC power to be used in your home.

So, it’s a beautiful sunny day and the solar panels on your roof are in full sun. The panels convert that sunlight into DC power which is converted to AC power by your inverter, and now you can use that energy in your home. Is it really as simple as that? Well yes, but there’s a bit more to it.

Once your solar system is generating power, that electricity is sent to your switchboard and from there you will either use it yourself ‘behind the meter’ or it will feed into the grid. 

Self-consuming the electricity generated by your solar system in your home is known as ‘behind the meter’ energy consumption. For example, if your solar system is producing electricity in the middle of the day and you have your air-conditioner on and your washing machine running, you’re using the electricity produced by your solar system behind the meter. This means you’re saving money at the rate you’d be spending if you ran those appliances in the evening and had to buy energy to power them.

But if you’re at work during the day and you’re not using any electricity at home, the energy which is being produced by your solar system will feed into the grid and your power provider will pay you a feed-in tariff for that electricity.

Sounds great, right? Either you’re at home, using your solar power for free, or you’re not using your solar electricity so you’re getting paid for it!

But there’s one more thing to consider, and this is where it gets tricky: At night your solar isn’t producing any electricity so, unless you have batteries, you have to buy it. However most people will be paying more for the power they consume than what they get for putting energy back into the grid.

If that’s you, it will be better to use your electricity behind the meter (ie. at home) as much as possible, rather than exporting it to the grid. By maximising the onsite utilisation of your energy, you’ll see the best payback.

It’s a good idea to keep this in mind when you’re first installing your solar system because the larger the solar system, the more electricity you’ll self generate and the more electricity you can use behind the meter. Plus, if your solar system is producing more power than you’re consuming, the surplus power is fed into the grid. So with a big enough system, you could use energy behind the meter while exporting to the grid at the same time (and being paid to do so!)

If you’re thinking, ‘I work all day and won’t be home to do my washing while the sun’s up, should I still get solar?’ The answer is absolutely!

There are always ways around this issue, including timers you can use to set your appliances to turn on in the middle of the day. Another good tip is to leave your heating/cooling on while you’re at work and your solar’s generating electricity. That way, when you come home in the evening your house will be warm/cool and you can turn the system down/off in the evening to avoid paying peak electricity rates.

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