How Does a Solar Battery Work? A Plain-English Guide for Homes

How does a solar battery work? In short, it stores the extra electricity your panels make during the day, then releases it to power your home at night. Your panels produce direct current (DC), an inverter manages the flow, and any solar you do not use straight away charges the battery instead of being exported. When the sun goes down, the battery discharges what it stored so you keep running on your own solar instead of buying power back from the grid.

How does a solar battery work, step by step?

On a sunny day your roof usually makes more power than the house is using. Without storage, that surplus flows out to the grid. Add a battery and the same surplus charges it up instead, so you build a reserve to draw on later.

1. Your solar panels generate DC electricity whenever there is daylight.
2. An inverter converts DC into the AC power your appliances use, and directs the flow between panels, home, battery and grid.
3. Power is used first by whatever is running in your home at that moment.
4. Any leftover solar charges the battery rather than being exported.
5. Once the battery is full, further surplus is sent to the grid.
6. In the evening and overnight, the battery discharges to run your home, and you only draw from the grid once it is depleted.

The core idea: a battery lets you use your own daytime solar at night, instead of exporting it cheaply and buying it back at a higher price after dark.

What is the difference between AC-coupled and DC-coupled batteries?

There are two common ways to connect a home battery, and the right one usually depends on whether you are starting fresh or adding storage to an existing solar system.

DC-coupled

A DC-coupled battery connects on the same side as your panels and works with a hybrid inverter. Solar charges the battery as DC before anything is converted, which means fewer conversion steps and slightly less energy lost along the way. It is a tidy option for new solar-and-battery installs designed together.

AC-coupled

An AC-coupled battery has its own inverter and connects on the AC side of your switchboard. Because it does not depend on replacing your existing solar inverter, it is often the simpler way to add a battery to a system that is already up and running. There is one extra conversion step compared with DC-coupling, but modern equipment keeps the difference small.

If you already have panels and want to store what you are currently exporting, our guide on adding a battery to existing solar walks through what is involved.

What are the main parts of a home battery system?

A home storage setup is more than just the battery box on the wall. A few components work together so power flows the right way at the right time.

• The battery: stores energy as DC, measured in kilowatt-hours (kWh) of usable capacity.
• An inverter: a hybrid inverter handles both solar and battery, while an AC-coupled setup uses a separate battery inverter.
• A battery management system: built into the battery to keep it charging and discharging safely and to protect its lifespan.
• Monitoring: an app that shows in real time what your solar, home, battery and grid are each doing.
• Optional backup wiring: a changeover setup so nominated circuits can keep running if the grid goes down.

Why store solar instead of sending it to the grid?

Most homes are busiest with power in the morning and evening, but solar makes the most energy in the middle of the day. That mismatch is the whole reason batteries exist.

In South Australia, where daytime sun is strong and grid prices are high, a lot of solar can go out to the grid for a modest return, only for the same household to buy power back at a higher rate once the sun sets. Storing that energy and using it yourself is usually worth more than exporting it. To see how the numbers stack up for a typical home, read our take on why you might be wasting your solar without a battery.

Rule of thumb: the more of your power use that lands after dark, the more a battery has to offer, because that is when it does its work.

How much of a battery's capacity can you actually use?

Batteries are rated in kilowatt-hours, but not every rating means the same thing. A couple of terms are worth knowing so you can compare fairly.

• Usable capacity is the energy you can really draw each cycle, which is what matters day to day.
• Round-trip efficiency describes how much energy comes back out compared with what went in, since a small amount is always lost in charging and discharging.
• Power output (in kilowatts) sets how many appliances the battery can run at once, separate from how much total energy it holds.

Getting the size right means matching your overnight usage, your solar system and your budget. Our solar battery buyers guide breaks the sizing question down in more detail.

Which solar batteries does eHomes install?

We install and service a range of quality home batteries, including Fox ESS, GoodWe and SolaX. The best fit depends on your existing solar, whether you want backup, how much you use after dark and the budget you are working to, rather than any single brand being right for every home.

We will talk you through the trade-offs in plain English and match the battery and inverter to your actual usage. Explore the options on our solar battery page, and for current incentives and finance see rebates and finance, which we keep up to date.

Frequently asked questions

Does a solar battery power my house during a blackout?

Only if it is set up for backup. Many batteries can keep nominated circuits running through an outage, but this needs the right inverter and backup wiring, and it is not automatic on every install. If keeping the lights on during a blackout matters to you, tell us up front so we can design the system to do it.

Can I add a battery to solar panels I already have?

Yes. An AC-coupled battery has its own inverter and connects to your switchboard, so in most cases you can add storage without replacing your existing solar. A quick check of your current system tells us the cleanest way to connect it.

Does a solar battery charge from the grid or only from solar?

By default it charges from your surplus solar. Many systems can also be set to charge from the grid at certain times, which can help if you are on a plan with cheaper off-peak periods. How you use that depends on your tariff and your goals.

How long does a solar battery last on a full charge?

It depends on the battery's usable capacity and how much power your home draws overnight. A battery sized to your evening and overnight usage is designed to carry most homes through until the sun comes back and recharging begins. Correct sizing is the key to getting a full night of stored power.

Are there rebates or finance to help with a battery?

Incentives and finance options change over time and vary by state, so we do not quote figures that may go stale. For what applies right now, see our rebates and finance page, which we keep current, then request a quote for pricing tailored to your home.