The huge leap forward in battery technology has seen an immense amount of interest in people looking to go off-grid, store their own solar energy (self-use) and become energy independent. Although the rapid pace of technology has resulted in some confusion over what is achievable and which battery system is best suited to an individual households. Costs can also vary wildly depending on the amount of energy storage capacity measured in kWh and type of inverter installed. Here we help explain some of the advantages of home battery systems, provide some battery reviews, give a price guide and compare several of the leading battery systems.
For those new to solar see our basic introduction to the different solar system types including grid-tie, off-grid and hybrid battery systems.
What is a battery ready system?
A battery ready system is a much like a common grid-connected solar system but uses a hybrid inverter rather than a common solar inverter. Modern all-in-one hybrid inverters have the battery connection and controls built-in which makes adding a battery much easier in the future. The down side is ‘battery ready’ or hybrid inverters are typically 20-40% more expensive and due to the rapid changes in technology a compatible battery may be difficult to find after a few years.
Can a battery be added to an existing solar system?
Yes a battery can be added to any grid-connected solar system using a specific type of system known as an AC coupled battery. A battery can be easily added using a AC battery system such as the Sonnen ECO and Tesla Powerwall 2. Retrofitting a battery can also be achieved using a special hybrid inverter designed for AC coupling such as the SMA Sunny Boy Storage inverters which can be used to retrofit the popular LG Chem battery. Soltaro and Goodwe also supply AC coupled battery inverters much like the SMA inverters.
If you have high powered backup requirements or need instantaneous backup like a UPS system (without a delay) you will should go for an advanced multi-mode inverter like the Australian made Selectronic SP PRO or Victron Multiplus. These high powered inverters are designed to operate in both on-grid and off-grid modes are and compatible with many of the leading battery systems.
An increasing number of lower cost ‘hybrid’ solar inverters are also 'battery ready' such as the Huawei SUN2000L and Sungrow SK5H-20 so it will become easier to add battery storage in the future.
Advantages of home battery systems
Reduce cost - Save money by using less energy from the grid
Reduce emissions - Reduce pollution from coal/gas power generators
Be blackout safe - Have power available during a blackout or emergency
Become energy independent - Generate, store and use your own energy
Disadvantages of home battery systems
Higher upfront cost - Adds much more to the total system cost
Complexity - Requires a hybrid inverter and monitoring equipment
Space - Should be installed in a secure safe area out of the sun
Do you need a battery for your home?
Unless you experience frequent blackouts the answer is generally no. For many people the cost of a battery system is simply too high, but this doesn't mean you can't take advantage of rooftop solar. For most households rooftop solar will reduce your electricity bills by 60% or much more depending on the amount of energy you use during the day as it is generated. For example it is possible to run energy intensive appliances such dishwashers, air-conditioners and washing machines for free using your solar energy during the day. Also you can receive credits for any excess energy fed back to the grid.
Smart home controls
Several modern solar inverters have inbuilt ‘demand management’ controls which can automatically switch on appliances when there is excess solar energy rather than sending it to the grid for little return. Also companies such as Solar Analytics make clever monitoring and control devices which can be added to any existing system which can be used for advanced monitoring and remote ‘smart’ control of appliances.
Hot water diverters
There are several add-on devices available to automatically heat hot water using excess solar energy which is in effect using hot water as energy storage. Fronius have an add-on system called the ohmpilot or there are other well known retrofit systems from Catch power and Powerdiverter.
Hot water systems store energy but unlike batteries which use chemical reactions so store energy, hot water systems simply store energy as heat. If you have electric hot water then by adding a timer or solar power diverter you can reduce energy costs by up to 30% by using excess solar energy to heat your water during the day.
How much does a battery system cost?
The cost of home battery systems depend on the size (capacity) of the battery and type of solar or hybrid inverter used. Typical household batteries can cost anywhere from $4000 up to $16,000 or more depending on the storage capacity measured in kWh (kilowatt hours) and type of hybrid or multi-mode inverter used.
As a general guide batteries cost between $800 to $1200 per kWh installed. For example the Tesla Powerwall 2 with 13.2kWh of storage capacity will cost around $14,000 fully installed while the 10kWh LG Chem RESU-H battery is closer to $9000 plus the extra cost of a compatible hybrid inverter and installation.
There are many different systems available which suit many different household energy needs. Here we have a comparison chart as how much the popular battery systems cost per kWh for a common household over the typical 10 year warranty term of a modern lithium battery. See more detailed pricing and upfront cost comparison charts in the detailed solar battery review.
Popular Home battery options
LG Chem RESU
DC coupled battery
The LG Chem RESU range of home battery systems are one of the most widely used and flexible battery options available. The popularity is due to LG chem’s quality and compatibility with a huge range of the home energy storage (hybrid) inverters and systems including the SolarEdge optimiser system. Available in three main sizes 6.5kWh, 10kWh and 13kWh, the RESU range is also one of the most affordable and reliable battery systems on the market.
Read the full LG Chem RESU review here
Tesla Powerwall 2
AC coupled battery
The Tesla Powerwall 2 is one of the most well known and most popular battery systems. Available in one size only the Powerwall 2 is an AC battery with a relatively large 13.5kWh capacity which is more than enough for the average household. The recent price rises bring it up to $10,500 plus installation so it is on the higher end of the price scale but is also offers some advanced features such as liquid cooling and inbuilt inverter/charger. However it still requires a solar inverter to operate with a solar array.
Read the full Tesla Powerwall review here
There are many lithium battery systems used for off-grid applications but not all lithium batteries are suitable for off-grid use. For smaller capacity systems there are several 48V options from LG chem and BYD but the ‘modular’ high capacity battery systems from manufacturers such as Simpliphi in the US and Powerplus energy in Australia are a more reliable, flexible choice. These modular batteries are known as ‘self-managed’ lithium batteries and can work with many of the dedicated off-grid multi-mode inverters.
See our detailed review of the leading off-grid solar battery systems here.
Solar Battery Comparison Chart
Below is a table of the most popular and common battery systems currently used in Australia. Some of these are AC batteries which can be retrofitted to existing solar installations such as the Tesla Powerwall 2, Sonnonbatterie and Enphase battery. There are also retrofit inverter options using the LG chem and BYD batteries. Ask your local licensed solar installer for more details and information.