If you’ve researched solar batteries at all, you’ve likely encountered terms like “round-trip efficiency” and “depth of discharge,” and honestly, it can be confusing. You want to know which battery offers the best value without needing to become an electrician to figure it out.
Many Australian homeowners want to take more control of their energy bills and rely less on the grid, especially with power prices continually increasing. However, when you start examining battery options, the specs can become overwhelming. Do you need AC or DC coupling? Does 90% efficiency mean it’s good, or just average?
At PSC Energy, we’re here to clear up some confusion. We’ll break down what solar battery efficiency means, explain how the most popular options (the Sigenergy SigenStor, Enphase IQ Battery 5P, and Tesla Powerwall 3) compare, and help you figure out which one might suit your home best.
In this article, you’ll learn about the following:
- Understanding Solar Battery Efficiency
- AC-Coupled vs DC-Coupled Solar Batteries
- Sigenergy SigenStor: Efficiency Overview
- Enphase IQ Battery 5P: Efficiency Overview
- Tesla Powerwall 3: Efficiency Overview
- Comparative Analysis of Each Battery’s Efficiencies
- FAQ: Solar Battery Efficiency
By the end of this article, you’ll understand what efficiency numbers matter, why some systems work better with certain setups, and which battery fits your lifestyle and budget.
Understanding Solar Battery Efficiency
When people talk about battery efficiency, they usually mean something called round-trip efficiency. This number tells you how much energy a battery can release after storing it.
If a battery has a round-trip efficiency of 90%, that means for every 10 kilowatt-hours (kWh) of energy you put in, you can only get 9 kWh back. The rest is lost as heat or during the conversion process.
Another term you’ll see is depth of discharge (DoD). This indicates how much of the battery’s energy you can use.
For example, if a battery has a 100% depth of discharge, you can use all of its stored energy without damaging it. However, if it’s 90%, you must leave 10% unused to protect the battery’s lifespan.
Both of these numbers matter because they impact value you get from your battery. A battery with high round-trip efficiency wastes less energy. One with a high depth of discharge lets you use more of what you’ve stored.
If you’re interested in solar batteries, you might want to check out the following article titled, Are Solar Batteries Worth It in NSW? PSC’s Ultimate Guide for 2025.
AC-Coupled vs DC-Coupled Solar Batteries
Before your battery stores energy, the electricity from your solar panels needs to be managed. That’s where coupling comes in.
There are two primary methods for connecting a battery to your home: AC coupling and DC coupling.
Let’s do a quick review of how electricity flows through your solar system. The panels harvest sunshine and generate DC (direct current) electricity.
Your home and the grid are powered by alternating current (AC) electricity. To transform DC to AC electricity, the power must pass through an inverter. Sounds simple, right?
Well, your home battery stores DC electricity only. So, it needs to pass through another inverter to transform it back to DC electricity.
And if the home needs energy or if you’re feeding the grid for a tariff, the DC electricity must pass through the same inverter to become AC electricity once again.
Now that the review is complete, let’s move on to coupling.
The way you connect your battery to your solar system affects the efficiency of your system.
DC-coupled Batteries:
When a solar battery is DC-coupled, that means the solar system feeds the battery directly. It doesn’t need to pass through the inverter, because both the solar panel and the battery produce and store DC electricity.
When your home needs stored energy, the inverter comes into play and converts DC electricity to AC electricity.
Because the energy is only converted once, you lose less power in the process. This makes DC-coupled systems more efficient, especially when you’re primarily storing solar energy for later use.
AC-coupled Batteries:
On the other hand, AC-coupled batteries convert the energy from DC to AC right after it leaves the solar panels, as we mentioned above.
Then, if the battery needs to store it, the system converts it back to DC to charge the battery. When you use the energy later, it’s converted to AC again for your home.
That means it goes through two or even three conversions, and each one wastes a little bit of energy.
If you’re installing a new solar and battery system from scratch, a DC-coupled battery can be more efficient.
However, if you already have solar panels with an existing inverter, adding an AC-coupled battery is easier. It won’t be quite as efficient, but it can still save you money and help you store extra solar power for when you need it.
If you’re interested in learning about types of solar batteries, you might want to check out the following article titled, AC-coupled Battery vs. DC-coupled Solar Batteries.
Sigenergy SigenStor: Efficiency Overview
The Sigenergy SigenStor is a new entry to the Australian market, but it packs some serious features. This battery is part of an all-in-one energy system that includes solar inverters, battery modules, and even EV charging, all managed by smart software.
In terms of efficiency, Sigenergy states a depth of discharge of 100%. That means you can use all the stored energy in the battery without reducing its lifespan. This gives you more usable energy from the total capacity.
However, the company does not list a specific round-trip efficiency percentage on their product page or datasheet for AC-coupled add-ons. That makes it hard to directly compare with others based on energy loss during storage and conversion.
For the DC-coupled complete energy system, the datasheet boasts a maximum efficiency of 98%. This installation method allows the solar to feed directly into the battery bypassing the inverter.
The battery is modular, allowing you to scale it to fit your specific needs. It comes in 5 kWh and 8 kWh modules, and you can stack them to reach a total of up to 48 kWh. This flexibility makes it a strong option if you plan to expand your system in the future.
Sigenergy also includes features such as AI-assisted energy planning and direct DC EV charging, which can enhance your overall energy efficiency if you own an electric vehicle.
These features are helpful if you’re looking to future-proof your home and reduce energy waste across your entire setup.
If you’d like to learn a bit more about the cost of SigenStor, we recommend you check out the following article titled, How Much Does the Sigenergy SigenStor Cost?
Enphase IQ Battery 5P: Efficiency Overview
The Enphase IQ Battery 5P is built for flexibility and safety. It’s an AC-coupled battery, which means it’s easy to install with existing solar systems that already use Enphase microinverters. This makes it a popular choice for upgrades and retrofits.
The battery has a usable capacity of 5.0 kWh, which means you can utilise all 5 kWh without needing to worry about keeping energy in reserve. Enphase batteries operate at or near 100% depth of discharge.
Enphase provides efficiency specs, too. The DC round-trip efficiency is 96%, which is excellent. However, since this is an AC-coupled system, you are more likely to see an AC round-trip efficiency of around 90% in real-world use.
This battery also features built-in microinverters, which enhance safety and provide greater control over its interaction with your solar panels and the grid. There are six in the battery, and if one malfunctions, the other five continue to convert DC to AC and back again without shutting down. There is no single point of failure.
The system uses passive cooling instead of fans, which makes it quieter and requires less maintenance. Enphase backs it with a 15-year or 6,000 cycles warranty, which is one of the longest warranties currently available. Every time a battery is fully charged and then discharged, we refer to that as a cycle. One more thing about the warranty: it’s whichever comes first – 15 years or 6,000 cycles.
The IQ Battery 5P is a solid choice for homes that already use Enphase solar equipment or for individuals seeking a simple, plug-and-play solution with good efficiency and long-term support.
If you’re interested in learning a bit more about IQ Batteries, you might want to check out the following article titled, How Much Does an Enphase IQ Battery 5P Cost?
Tesla Powerwall 3: Efficiency Overview
The Tesla Powerwall 3 is one of the most well-known solar batteries on the market. It’s designed for people who want a large, powerful battery that works smoothly with their solar system.
This instalment to the Powerwall lineup comes with an integrated solar inverter, so it’s ready for new installations or complete system upgrades.
Tesla lists an AC round-trip efficiency of 89%, which is average for a system that includes both storage and conversion in one unit. That means for every 10 kWh of energy you send to the Powerwall, you’ll get about 9 kWh back for use in your home. Please note that this is only applicable for an AC-coupled connection.
Powerwall can also be installed as a DC-coupled battery. The solar system on the roof can feed directly into the battery, just like SigenStor can. The DC-efficiency is 97.5%.
One standout feature of the Powerwall 3 is its 100% depth-of-discharge capability. This means you can use all 13.5 kWh of its usable capacity without holding any back. That gives you more value from every full charge, especially during extended outages or peak energy times.
The Powerwall 3 can provide up to 11.5 kW of continuous power output, making it strong enough to support larger homes or those with high energy usage.
Unfortunately, in NSW, the local energy distribution network requires all inverters to be capped at a maximum of 5 or 10 kW per phase, depending on the situation.
Tesla backs the Powerwall with a 10-year warranty, and it’s built with an IP67 rating, meaning it can withstand harsh weather conditions, including heavy rain and dust storms. That makes it a good fit for many parts of Australia.
If you’d like to learn more about the price of a Powerwall 3, you might want to check out the following article titled, How Much Does a Tesla Powerwall 3 Cost?
Comparative Analysis of Each Battery’s Efficiencies
Each of these batteries has strengths that suit different types of homes. If you’re trying to decide which one is best for you, it helps to think about your energy goals, your current solar setup, and how much power you use.
The Enphase IQ Battery 5P stands out. It offers 96% round-trip efficiency on the DC side and around 90% on the AC side.
It’s an excellent fit for people who already have an Enphase system or want something easy to install with an existing solar system. It also comes with a 15-year warranty, which gives peace of mind for long-term use.
If you care about depth of discharge and full energy usage, the Tesla Powerwall 3 is a strong choice. It gives you access to 100% of its stored energy and boasts a high usable capacity of 13.5 kWh.
It’s ideal for larger households or individuals who require additional backup power. Its 90% round-trip efficiency is solid, especially for an all-in-one unit with a built-in inverter. Of course, that’s only for retrofits. For an entire energy system that’s DC-coupled, the efficiency rises to 97.5%.
If you’re looking for a flexible and scalable system, the Sigenergy SigenStor is worth a look. Its depth of discharge is 100%, and you can expand the system as your needs grow. It also supports features like EV charging and AI-based energy management. It’s a good option if you’re building a new system and want room to grow.
Your choice may also depend on how your current solar setup is built. If you already have solar panels and want to add a battery without making significant changes, an AC-coupled battery, such as the Enphase or Tesla, is easier to integrate. If you’re starting fresh or planning a full system upgrade, DC-coupled setups like Sigenergy can give better efficiency and more control.
If you’re interested in learning a bit more about the VPP portion of the battery rebate, you might want to check out the following article titled, NSW Battery VPP Rebate Explained: What You Need to Know.
Final Thoughts on Battery Efficiency
Solar batteries can help you store more of your own solar energy and cut down your power bills. But not all batteries work the same way, and efficiency plays a big part in how much value you receive.
Also, think about how the battery will integrate with your current setup. AC-coupled batteries are easier to add to existing solar systems. DC-coupled batteries are better for new builds where you want the most efficient setup.
In the end, the best battery for you depends on your home, your energy needs, and your long-term goals. Now that you know what the numbers mean and how the top batteries compare, you’re ready to make a confident choice. Your friends at PSC Energy are here when you’re ready. It’s what we do.
If you’re interested in learning a bit more about the federal solar rebate, also known as the Federal Cheaper Home Batteries Program, you might want to check out the following article titled, What the 2025 Federal Election and the Government Rebate Means for Solar Batteries in Australia.
FAQ: Solar Battery Efficiency
What is round-trip efficiency in a solar battery?
Round-trip efficiency measures how much energy a solar battery can store and then return for use. If a battery has 90% round-trip efficiency, it means you get back 9 kilowatt-hours of usable energy for every 10 kilowatt-hours stored. The rest is lost during the conversion and storage process. Higher round-trip efficiency means less energy wasted and more value from your solar setup.
What does depth of discharge (DoD) mean for a battery?
Depth of discharge (DoD) tells you how much of a battery’s energy you can use without damaging it. A 100% DoD means you can use the full capacity, while a 90% DoD means you must leave 10% unused. A higher DoD gives you more usable energy and is better for maximising the return on your solar investment.
Is a DC-coupled or AC-coupled battery better for efficiency?
DC-coupled batteries are generally more efficient because energy is only converted once, straight from the panels to the battery and then to your home. AC-coupled batteries convert energy multiple times, resulting in increased energy loss. However, AC-coupled systems are easier to install with existing solar setups, making them a convenient option for many homeowners.
Can I add a solar battery to my existing solar panel system?
Yes, most homes can add a battery to an existing solar panel system. AC-coupled batteries, such as the Tesla Powerwall 3 and Enphase IQ Battery 5P, are designed for this purpose. They work independently of your current inverter, which makes installation faster and simpler. This is ideal if you want to boost your solar storage without replacing your whole system.
Which solar battery gives the most usable energy?
The Tesla Powerwall 3 offers 13.5 kWh of usable energy with a 100% depth of discharge. This means you can use every bit of energy it stores. It’s ideal for high-energy households or those seeking reliable backup power in the event of an outage.
What’s the best solar battery for future upgrades?
The Sigenergy SigenStor is designed for scalability. You can start with a few modules and add more later as your energy needs grow. It also supports direct EV charging and smart energy management, making it a strong choice for homeowners who want to future-proof their setup.
How long do solar batteries last?
Most solar batteries are designed to last 10 to 15 years. The Enphase IQ Battery 5P comes with a 15-year warranty, while the Tesla Powerwall 3 offers a 10-year warranty. Battery lifespan can vary depending on how often it is charged and discharged, as well as the operating conditions under which it is used.
Do solar batteries work during a power outage?
Yes, if your system is set up for backup. The SigenStor, the Tesla Powerwall 3, and the Enphase IQ Battery 5P support seamless backup during outages. They can power essential appliances when the grid goes down, giving you more energy security at home.
