Fast read
Yes, you can add a solar battery to your existing solar system. Most systems are compatible with AC-coupled batteries, which connect between the solar inverter and your home's switchboard. This allows excess solar energy to charge the battery for later use.
It's important to ensure your system generates enough electricity to justify the battery. If not, you might need to expand your solar capacity. When choosing a battery, consider your evening energy usage and whether you want backup power during outages.
Purchasing the full required capacity upfront is advisable, as future expandability isn't always guaranteed.
Can you add a solar battery to your existing solar system?
Batteries can potentially be added to most existing solar systems. While many solar systems are sold as being “battery ready” or “battery upgradeable’. A battery should be able to be added to any existing solar system.
In this case, what is called an AC-coupled battery is installed. In this situation, the battery which requires a “ battery inverter” is installed between the solar inverter and the home’s main switchboard. Sensors, usually current transformers are connected to the meter board. This means they can sense when generated from the solar system is greater than the electricity being used in the home.
Essentially, measuring the amount of power being sent back to the grid. When the monitoring system sees the excess power being generated. It then uses this electricity to charge the battery and store it till it is required for use within the house at a later time.
There are several options on the market now for AC-coupled batteries with the most well-known being the Tesla Powerwall. However, there are several well-recognised other options including, Sungrow, Sonnen, and Victron among others to choose from.
DC-Coupled Solar Batteries
The other type of battery available is DC coupled whereby the battery is directly connected to the solar panels. The DC-coupled battery is more suitable when you a designing a solar system from scratch with no existing solar system on the roof. The advantage of a DC-coupled or a hybrid solution is that the battery inverter and solar inverter are integrated into a single unit. With AC coupled, however, a separate solar inverter is required in addition to the battery inverter. It is also worthwhile to note that as network companies become more stringent on allowable capacity. The hybrid has an advantage as it is counted as just one inverter.
Basically, all grid-connected solar systems in Australia have the potential to have batteries added. The key criterion is having the electricity generation capacity to charge the battery.
The first thing to look at if you would like to add a battery to your existing solar system is to make sure you have enough solar capacity. Clearly, there is no point in adding a battery unless you have the electricity available from your solar system. So the first thing to do is to take a look at your online monitoring to see how much electricity is exported to the grid on a regular basis. As well as on a daily basis.
Exporting your electricity
Ideally, you want to see that you are exporting more electricity to the grid than the capacity of the battery so that under normal circumstances the battery will be fully charged and available daily. If this is not possible you will need to first look at expanding your current solar system. This would likely mean that you are installing an additional solar system in parallel to the existing one. However, if your existing system is older (say 10 years or more). It may be worth removing the old system and starting from scratch.
It is also worth considering what size battery you would need and why. While storing the electricity in a battery is great, it is only as good as your ability to use it. So you should also look at how much power you use overnight that could be supplied from the battery. If there are other peak periods in the middle of the day when solar may not provide all the power for the household needs at that time a battery could be used.
What we recommend for your existing solar system
It is recommended to consider the average evening consumption to get the most value from the battery. If you go too big and can’t use the full capacity regularly the value and return diminishes. The exception would be if you are looking for the battery to guarantee some level of backup capacity in the case of a blackout you can oversize the battery and reserve capacity that is only used available to be used if connection to the grid is lost.
Also, consider carefully when batteries are sold on the basis of their expandability. With the best of intentions, an expandable battery offer can be selected. Only to find out 2 or 3 years down the track that that option no longer exists. So it might be prudent to purchase the storage capacity you require in one transaction to avoid this potential dilemma.
