How solar, batteries and solar + battery work

Before you compare quotes, it helps to know what each part of a system actually does. This guide covers the three questions we're asked most: how solar works, how a home battery works, and what changes when you put the two together.

Part 1: How solar works

Solar panels are made of cells that turn sunlight into electricity. They produce direct current (DC), but your home runs on alternating current (AC), so the panels connect to an inverter, which converts the power into a form your appliances can use.

There are two common ways to do this. A string inverter is one box, usually mounted near your switchboard, that the panels feed into. Microinverters sit behind each panel and convert power right there on the roof. Our guide to microinverters vs string inverters explains the difference.

From the inverter, power goes into your switchboard. Your home uses solar first. If the panels are making more than you need, the extra flows out to the grid and your retailer may pay you a feed-in tariff for it. When the panels aren't making enough, such as early morning, evening and overnight, you draw power from the grid as normal.

A few things worth knowing:

• Panels work on cloudy days, just less. Output is highest around the middle of the day and in summer.
• Shade matters. Even partial shade from trees, chimneys or neighbouring buildings can reduce output.
• A standard grid-connected solar system switches off during a blackout. This is a safety requirement so it doesn't send power into lines that workers may be repairing.

Part 2: How a home battery works

A home battery stores electricity so you can use it later. Most home batteries today use lithium-based cells, managed by a battery management system that controls charging, discharging and temperature.

Like solar, a battery needs an inverter, because it stores DC power. Some batteries have their own inverter built in. Others connect to a hybrid inverter that runs both the panels and the battery.

Through the day, a battery charges from spare solar that would otherwise be exported. In the evening, when the sun goes down and your household gets busy, it discharges to power your home instead of buying from the grid. When it's empty, you go back to grid power until it charges again.

Batteries are sized by usable capacity in kilowatt-hours (kWh), meaning how much energy they can store and deliver, and by power output in kilowatts (kW), meaning how much they can supply at once. Both matter, which is why we cover sizing in what size solar system or battery do I need?

Part 3: How solar and a battery work together

Put solar and a battery together and your home follows a simple daily pattern.

Morning. As the sun comes up, the panels start covering your home's use. The battery may still be supplying some power if it has charge left from yesterday.

Middle of the day. Solar is at its peak. Your home uses what it needs, the battery charges from the spare, and anything left over is exported to the grid.

Evening and overnight. Solar fades and the battery takes over, covering lights, cooking, TV and other evening loads. When it runs low, the grid fills the gap.

The system decides all of this automatically. Most systems come with an app so you can see what your panels are making, how full the battery is and what you're using.

A battery can also be set up to keep power on during a blackout, but this isn't automatic. It has to be designed in. Our guide will my battery work in a blackout? explains how backup works.

Is solar, a battery or both right for you?

Solar on its own suits most homes with a reasonable roof and daytime use. A battery adds the most value when you use a lot of power in the evening and have spare solar to fill it. Whether a battery is worth it depends on your usage, your tariff and the system cost, which we cover in is a home battery worth it in NSW?

We've been doing this for more than 20 years and have completed over 4,000 installs with our own in-house electricians. If you'd like advice for your home, see our solar and battery storage pages or ask for a free quote.

Frequently asked questions