Solar inverter upgrades — when your old inverter is holding back your system.

Melbourne's eastern suburbs were among the earliest suburban areas in Victoria to embrace rooftop solar, driven by strong state incentives in the late 2000s and a population that was ready to invest in reducing electricity bills. A lot of those systems went in between 2010 and 2016.

The panels themselves — mostly monocrystalline or polycrystalline silicon — typically have 25-year performance warranties and lose capacity slowly, at around 0.5% per year. They're probably still producing close to what they always did.

The inverter is the component with a shorter life expectancy. The electrolytic capacitors that handle the DC bus, the cooling fans, and the power electronics all have design lives of around 10 to 12 years under normal operating conditions. A system installed in 2012 is now 14 years old. The inverter may still be running, but it's likely operating below its rated output — and may be doing so invisibly.

Signs that an inverter is underperforming

The most reliable way to know is monitoring data over time. If you've had a monitoring system in place and can compare year-on-year production for the same period, a meaningful decline in output — 20% or more, adjusting for any obviously different weather — is a strong indicator of inverter degradation rather than panel degradation.

Without good historical data, there are other signs:

Frequent fault codes or error messages. An aging inverter will throw more faults — grid voltage or frequency warnings, isolation faults, overtemperature events. Some of these indicate genuine grid conditions; a pattern of them across different conditions suggests the inverter's own sensing or protection circuits are deteriorating.

Inconsistent daily generation figures. A healthy inverter on a sunny day in autumn produces predictably. If generation varies widely between similar weather days, the inverter is the most likely cause — panel soiling or shading would produce more consistent degradation rather than day-to-day variation.

The inverter runs hot or the fan is noisy. Capacitor degradation causes increased internal heating. If the inverter enclosure is unusually hot to the touch or the fan runs continuously even when ambient temperature is moderate, the internal components are working harder than they should.

The inverter is displaying a reduced output limit. Some inverters self-derate when they detect internal faults — they keep running but cap output to protect the hardware. This shows up as consistent generation that's below what the panel capacity should produce on good days.

The manufacturer no longer supports the model. This is worth checking regardless of visible symptoms. If the inverter's firmware is no longer updated, it may not comply with current grid requirements. If the manufacturer is no longer trading — which applies to several brands that were popular in 2010–2014 — replacement parts don't exist and the unit cannot be repaired.

AS/NZS 4777 compliance

AS/NZS 4777 is the Australian and New Zealand standard for grid connection of energy systems via inverters. It specifies the electrical performance requirements for inverters — voltage and frequency ride-through, reactive power capability, export limiting, and protection settings.

The standard has been updated since the initial wave of solar installations. Inverters approved under earlier versions may not meet the current requirements for reconnection to the grid after a fault, or may not support the export control settings that some distributors now require for grid stability.

In Victoria, the distributor (CitiPower or United Energy in the eastern suburbs) can require that inverters connected to the grid meet current AS/NZS 4777 requirements. A replacement inverter needs to be a model on the Clean Energy Council's approved inverter list, which confirms it has been tested to the current version of the standard.

This compliance requirement also applies when adding a battery inverter to an existing solar system — both the solar and battery inverters need to meet the current standard.

Clean Energy Council accreditation

Solar work in Australia — installation, repair, and upgrade of grid-connected solar systems — requires a licensed electrician who holds Clean Energy Council (CEC) accreditation. This is separate from an electrical licence; it's a specific accreditation for solar work that requires demonstrated competency and ongoing professional development.

An inverter replacement is solar work. It involves disconnection and reconnection of the grid-connected system, and the new inverter needs to be commissioned and tested correctly. Having it done by a CEC-accredited installer also means the work is eligible for any applicable certificates under the Small-scale Renewable Energy Scheme (SRES) — though for a direct inverter replacement rather than a new system, the certificate entitlement is typically zero (certificates are generated by new capacity, not replacement components).

The practical point is to verify CEC accreditation before engaging anyone for this work.

What a hybrid inverter enables

A standard solar inverter does one job: convert DC from the panels to AC for household use and grid export. When the panels aren't producing — evenings, cloudy days, winter — you draw from the grid.

A hybrid inverter adds battery integration. It manages three energy flows simultaneously: the panels, the battery, and the grid. When the panels produce more than the household needs, the hybrid inverter charges the battery. When household demand exceeds panel production, it draws from the battery first before going to the grid.

The significant thing about replacing an aging standard inverter with a hybrid is that it positions the home for battery storage without requiring a full electrical redesign later. If you install the hybrid inverter now without a battery, you add the battery when the budget allows — plugging it into an inverter that's already designed to accept it. This is substantially less disruptive than retrofitting battery capability to a home with a standard inverter already in place.

DC-coupled battery systems require a hybrid inverter from the outset. AC-coupled systems — where the battery has its own separate battery inverter — can work alongside a standard solar inverter, but they're generally less efficient because the energy undergoes multiple conversion steps. DC-coupling through a hybrid inverter is the more efficient arrangement when you're replacing the inverter anyway.

What the switchboard needs

Replacing an inverter involves more than swapping one box for another. The switchboard needs to accommodate the new unit.

An inverter replacement requires:

A correctly rated isolator. An AC isolator at the inverter and a DC isolator at the array are required. The ratings need to match the new inverter's specifications, and the existing isolators may not be appropriate for a higher-capacity replacement.

An appropriately rated circuit breaker on the inverter circuit. The circuit breaker on the solar circuit at the switchboard needs to be rated for the inverter's maximum output current. Upsizing the inverter may require upsizing the breaker.

Export limiting capability if the distributor requires it. Some network areas require export limiting — capping the amount of power the system can push back to the grid. The new inverter needs to support this, typically via a CT clamp on the consumer mains supply or via the distributor's DER register and remote control capability. This is an increasingly common requirement in areas with high solar penetration.

Space in the switchboard for battery management equipment. If you're installing a hybrid inverter ahead of a future battery, the switchboard needs to be able to accommodate the additional circuit and any changeover equipment the battery backup configuration requires. This is worth planning for at the time of the inverter replacement rather than discovering it's insufficient later.

Switchboard condition is often the thing that determines whether an inverter upgrade is straightforward or whether it requires broader work. Boards with ceramic fuses, no safety switches (RCDs), or insufficient capacity for the additional circuits need upgrading first. In an older eastern suburbs home, this is common enough to be the expected case rather than the exception.

What the upgrade process looks like

An inverter replacement is typically a day's work for a CEC-accredited electrician. The sequence:

1. Isolate the system at the grid connection point and at the array
2. Remove the old inverter and associated isolators
3. Install the new inverter, mounting it in the same or a revised location
4. Replace isolators as required
5. Commission the new inverter — configure grid settings, protection parameters, export limits, and monitoring
6. Test performance against the panel array's expected output
7. Register the new inverter with the network distributor if required

If the switchboard needs work, that runs concurrently or immediately prior.

The monitoring system also needs to be set up again. Most modern inverters have app-based monitoring that gives you real-time production data, historical generation charts, and fault alerts. Getting this running properly is worth prioritising — it's the visibility you need to know whether the system is performing correctly over the years ahead.

If your solar system is more than ten years old and you're not sure what state the inverter is in, contact us through the solar and battery page and we'll assess it.