Adding a Battery to an Existing Solar System

Start by identifying your inverter

Go and look at it. The answer to most of the cost question is written on the front.

If you have a hybrid inverter

A hybrid inverter was built to run a battery, whether or not one was installed at the time. Adding a compatible battery is the cheapest path there is, and it is the scenario behind our entry-level pricing. The battery mounts, connects to the inverter, gets commissioned, and you are done.

The catch is compatibility: a hybrid inverter will generally only work with batteries on its approved list. If your inverter is an older model, that list may be short or may include batteries that are no longer sold.

If you have a standard string inverter

This covers most systems installed in Brisbane before roughly 2019. Your inverter converts panel output to AC and has no battery capability. You have two options:

• AC-coupled battery: an all-in-one battery with its own inverter built in, installed alongside your existing system. Your solar setup is untouched. Simpler, and it keeps whatever warranty remains on the original inverter.
• Replace the inverter with a hybrid: makes sense when the existing inverter is near end of life anyway, or when you want everything managed by one system. Usually the more efficient long-term answer, but it is a bigger job.

Which of these is right is genuinely situational. An eight-year-old inverter that is about to fail is a different decision from a two-year-old one still under warranty.

If you have microinverters or optimisers

These are AC systems, so a battery is added AC-coupled. Straightforward in principle, but the monitoring and control side needs thought so the two systems do not fight each other.

What else gets checked

The switchboard

Older boards frequently need work before a battery can be added: RCD protection, spare ways, or simply physical room. In some Brisbane homes this is the largest single line on the quote, and there is no way around it. It is a compliance requirement, not an optional extra.

Where the battery goes

AS/NZS 5139 governs where batteries may be sited: clearances, what may be on the other side of the wall, separation from exits and habitable rooms, and protection from heat. A west-facing wall in a Brisbane summer is a poor choice even where it is technically allowed. Garage walls and shaded south or east elevations are usually the good options.

Your existing system's size

There is little point pairing a large battery with a small array that never produces enough surplus to fill it. If you have a 3 kW system from 2013 and you want 20 kWh of storage, the honest advice is often to expand the array first, or at the same time.

Will your feed-in tariff change?

This is worth checking before you commit. Households on legacy high feed-in tariffs need to confirm with their retailer and distributor whether modifying the system affects that arrangement. In most cases adding storage is fine, but it is your money and it is a five-minute phone call.

Is a retrofit worth it?

It depends on one thing more than any other: how much of your generation you currently export. If you are exporting most of what you make and buying it back at night, a battery has a lot of margin to work with. If you already self-consume nearly everything you generate, the case is much weaker and we will say so.

Pull twelve months of your bills, or better, your interval data from your retailer, before you take anyone's word on payback. We will do that analysis with you, and if it does not stack up we would rather tell you now than sell you a battery you regret.