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 system is best suited to an individual households. Here we help explain some of the advantages of home battery systems, provide some battery reviews 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.
You can always add a battery to any grid-connected solar system. If you don’t need a battery urgently for backup power requirements you can always add a battery at any time to any existing grid-connected system using an AC battery or an advanced multi-mode inverter like the Selectronic SP PRO.
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 well known systems from Catch power and Powerdiverter.
Hot water systems store energy but unlike batteries which use chemical reactions so store energy, hot water systems store energy as heat. If you have electric hot water then by simply adding a timer or solar power diverter you can reduce energy costs by up to 30% by using excess solar energy during the day.
How much does a home battery system cost?
The cost of home battery system depends on the size (capacity) of the battery and type of solar or hybrid inverter used. Typical household batteries can cost anywhere from $3000 up to $15,000 or more depending on the storage capacity measured in kWh (kilowatt hours). As a very general guide batteries cost between $1000 to $1200 per kWh installed. For example the Tesla Powerwall 2 with 13.2kWh of storage capacity will cost around $14,000 fully installed.
There are many different systems available which suit many different household energy needs. Here we have provided a guide as how much a typical battery systems will cost for a typical 3 bedroom home.
Popular 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
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 others 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 non-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.
Home Solar Battery Comparison
Below is a table of the most popular and common battery systems currently used in Australia. Some of these 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.