Inverter guide
Microinverters vs string inverters and optimisers: which suits your Melbourne roof?
Solar micro inverters turn each panel’s power into AC under the panel, and optimisers track each panel before one central inverter converts it. On a Melbourne roof they pay off where shade falls on part of the array, or the panels face more ways than a string or hybrid solar inverter has trackers. An east-west roof alone doesn’t need them: in Mount Waverley, Melbourne, PVGIS puts east and west faces at 87% and 86% of a north face’s yearly output, and each face can have its own tracker.
Our previous website listed Sungrow, Fronius and Alpha ESS inverters, all string or hybrid models; which brands we install today is being confirmed. Enphase warrants its IQ8 microinverters for 25 years in Australia if they stay online, against 5 to 10 years on those models, but a fault means a roof visit.
Updated
What are solar micro inverters and optimisers?
Every solar system has the same job to do: panels make direct current (DC), and your home and the grid run on alternating current (AC). The four set-ups differ in where each panel’s best output is tracked and where DC becomes AC.
String inverters
A string inverter is one box on the wall. The panels are wired in series into strings, and each string runs to a maximum power point (MPP) tracker that sets one operating point for every panel in it. String inverter solar panels are the simplest set-up, with no electronics on the roof, and the inverter sits where an electrician can reach it.
Hybrid inverters
A hybrid is a string inverter with a battery connection: it sends daytime solar to the home, the battery and the grid, then runs the home from the battery after dark. Its panels connect in strings, so everything here about strings applies to hybrids too (more on how hybrid inverters work).
Microinverters
A microinverter is a small inverter mounted under each panel that converts that panel’s output to AC on the roof. Enphase, whose IQ8 microinverters are one example, says that with its microinverters “each solar panel operates independently”, so shade on one panel lowers that panel alone. AC cable runs down to the switchboard, and there is no inverter on the wall.
Optimisers (DC optimisers)
A solar panel optimiser is a small unit under each panel that tracks that panel’s best output, then sends DC down to a central inverter for conversion. Some belong to one maker’s system: SolarEdge says its optimisers are “specifically designed to work with SolarEdge inverters”. Others are add-ons: Tigo’s TS4-A-O is “fully compatible with thousands of different inverter models from more than 50 inverter brands” and can go on just the panels that are shaded, which Tigo calls “selective deployment”.
String, hybrid, micro and optimisers compared
| Set-up | Where DC becomes AC | One panel in shade | What the app shows | Adding a battery | Maker’s warranty (example) |
|---|---|---|---|---|---|
| String inverter | One inverter on the wall | Lowers the output of its whole string | The system and each string | A battery with its own inverter (AC coupled), or a swap to a hybrid | Fronius Primo string inverter: 5 years Fronius Warranty Plus as standard, or 10 years free when registered on Solar.web within 30 months of delivery |
| Hybrid inverter | One inverter on the wall | Lowers the output of its whole string | The system, each string and the battery | Connects straight to the inverter (DC coupled), now or later | Sungrow SH-RS hybrid inverter: 10 years from installation in Australia (at most 11 years from manufacture) |
| Microinverters | Under each panel, on the roof | Lowers that panel only | Each panel | A battery with its own inverter (AC coupled) | Enphase IQ8 microinverters: 25 years from activation, if kept online |
| Optimisers | One inverter on the wall | The other panels keep their own best output | Each panel | Depends on the inverter: a hybrid takes one directly | SolarEdge S440 and S500 power optimisers: 25 years; Tigo TS4-A-O: 5 years, or 25 if kept online |
One trade-off cuts both ways. A microinverter that fails takes out one panel, while a central inverter that fails stops every panel feeding it. But a central inverter is replaced from the ground, and a faulty microinverter or optimiser means work on the roof.
Shade and split roofs: when panel-level electronics pay off
In a string, every panel carries the same current, so one panel in shade holds its string back. Each panel’s bypass diodes let the current skip a shaded section, which keeps the string working but gives up that section’s output, and the tracker settles on one operating point for the whole string. With microinverters or optimisers, every unshaded panel keeps its own best output.
Split roofs are a different problem. Where a roof has no good north face, panels often go east and west: in Mount Waverley, Melbourne, PVGIS puts a 6.6 kW array at 20° facing east at 87% of what it makes facing north over a year, and facing west at 86%. East and west panels peak at different times of day, so they shouldn’t share a string. On a string or hybrid inverter each face goes on its own tracker, and the Sungrow, Fronius and Alpha ESS models shown here have 2 to 4 trackers.
Panel-level electronics are worth pricing when:
- Shade crosses the array for hours. A tree, chimney, flue or a neighbour’s second storey shades part of the panels through the middle of the day, not only early or late.
- The panels face many ways. Three or more roof faces, or more faces than the inverter has trackers.
- A roof face fits only a few panels. Each tracker needs a string long enough to reach the inverter’s working voltage, and a small face may not make one.
- You want to see every panel. Panel-level monitoring shows a weak or failed panel straight away.
They usually aren’t needed on an unshaded roof, or one with two faces on separate trackers. Leaving the most shaded spot without panels is another option.
Panel-level monitoring and safety
Monitoring
A string or hybrid inverter measures what each string makes, so its app shows the system, each string and any fault codes, but not one panel inside a string (iSolarCloud for Sungrow, Solar.web for Fronius and the AlphaESS app for Alpha ESS); finding a weak panel takes an electrician’s test. Microinverters and optimisers report every panel: Enphase says its microinverters “track every panel’s output”, and they report to the Enphase App; SolarEdge’s Home Hub inverter lists “built-in panel-level monitoring”.
Panel-level data depends on the internet, and so can the warranty. Enphase’s Australian warranty requires the microinverters to be registered, and connected to the internet through an Enphase gateway (the warranty calls it an Envoy), within 45 days, and to stay connected. Tigo’s optimiser warranty runs 5 years, or 25 if the system stays connected to its platform.
Safety
Panels in a string are wired in series, so their voltages add up, and the cable from the roof to the inverter carries DC whenever the sun is up, even with the inverter switched off. The DC isolator on that cable needs care too: Energy Safe Victoria wants it checked at every service, at least every 2 years, because as its casing ages it can let moisture in, which is a fire risk.
Panel-level electronics limit that DC. With microinverters it stays under each panel: Enphase’s installer page says “Low-voltage system keeps your solar safe and reliable”, and its microinverters have built-in rapid shutdown. Optimisers still carry string voltage to the inverter while the system runs, but cut it when the system stops: SolarEdge’s drop to 1 V each when they are disconnected from the inverter or it is switched off, and Tigo’s TS4-A-O adds rapid shutdown through a Tigo Access Point (TAP) and Cloud Connect Advanced (CCA). Whatever the system, solar wiring is work for a licensed electrician: look, don’t touch.
Batteries with each type
How a battery joins the system depends on the inverter. Solar Victoria’s Solar Battery Buyers Guide sets out the options.
- Hybrid inverter: the battery connects straight to the inverter (DC coupling), now or later. Each maker lists the batteries its hybrids take (Sungrow: Sungrow high-voltage batteries; Fronius: Fronius Reserva, BYD Battery-Box Premium HVS/HVM and LG RESU FLEX, per Fronius; Alpha ESS: Alpha ESS SMILE-G3 9.3 kWh modules, 1 to 4 in series). If the battery comes later, Solar Victoria warns that “any ‘hybrid’ inverter you install now could be obsolete by the time you purchase and install the battery”.
- String inverter: Solar Victoria says “The existing solar inverter can either be replaced or a second inverter added that is dedicated to the battery.” A dedicated battery inverter is AC coupling.
- Microinverters: Solar Victoria says a microinverter system needs a battery with its own dedicated inverter (AC coupling), and adds: “This option is relatively easy if you use a battery with an in-built inverter.” Enphase’s own IQ Battery 5P with FlexPhase is one: an all-in-one AC-coupled battery with six built-in microinverters.
- Optimisers: it depends on the inverter they feed. SolarEdge’s Home Hub inverter lists “high efficiency DC-coupled storage” with SolarEdge Home Battery, LG RESU10H Prime and LG RESU16H Prime batteries. Add-on optimisers on a hybrid leave its battery connection as it was.
What panel-level electronics add to the price
You pay for more hardware and more roof work. A string or hybrid system has one inverter; a microinverter system has one per panel plus a gateway for monitoring; an optimiser system has one optimiser per panel as well as the central inverter. Each unit is mounted and wired on the roof.
Part of the extra buys a longer warranty: 25 years on Enphase’s IQ8 microinverters and 25 years on SolarEdge’s optimisers, against 5 to 10 years on the Sungrow, Fronius and Alpha ESS models shown here. Read the conditions, though. Enphase’s warranty doesn’t cover the labour to take a faulty unit off the roof and fit its replacement, Enphase and Tigo tie theirs to an internet connection, and your Australian Consumer Law rights apply alongside any maker’s warranty.
We don’t publish a price list. We look at your roof, its shade and your switchboard, then give you a fixed installed price for the design that suits it.
What we install and why
Our previous website listed these Sungrow, Fronius and Alpha ESS inverters; which brands we install today is being confirmed, and your quote names the exact model.
- Sungrow SH-RS hybrid inverter: hybrid; MPP trackers: 2 (5 and 6 kW) or 4 (8 and 10 kW).
- Sungrow SH-T three phase hybrid inverter: hybrid; MPP trackers: 3 (SH15T to SH25T).
- Fronius Primo GEN24 and Symo GEN24 hybrid inverter: hybrid; MPP trackers: 2.
- Fronius Primo string inverter: string; MPP trackers: 2.
- Alpha ESS SMILE-G3-S5 hybrid inverter: hybrid; MPP trackers: 2.
Every one is a string or hybrid model; none is a microinverter or an optimiser. What string and hybrid inverters offer:
- A battery now or later. A hybrid connects one directly, with no second inverter.
- One box on the wall. It is serviced, replaced or upgraded without going on the roof.
- Split roofs on separate trackers. East and west faces each get their own tracker.
- The trade-off is the warranty. 5 to 10 years on the inverter, against 25 years on Enphase’s microinverters.
If your roof has heavy shade or many faces, tell us when we quote and we will talk through the options, including whether panel-level electronics are worth it for your roof.
Microinverters and optimisers: your questions
Are micro inverters better than a string inverter?
On a shaded roof, or one with panels facing many ways, usually yes: each panel works on its own and reports its own output. On an unshaded roof, or with east and west faces on separate trackers, a string or hybrid inverter does the same job from one box on the wall, and a hybrid takes a battery directly, where microinverters need one with its own inverter.
What does a solar panel optimiser do?
It sits under one panel and tracks that panel’s best output, so shade on it doesn’t pull the rest of the string down, then sends the power as DC to a central inverter. SolarEdge’s optimisers are designed to work with SolarEdge inverters; add-on optimisers such as Tigo’s TS4-A-O fit many other inverters and can go on just the shaded panels.
Is a DC optimiser the same as a microinverter?
No. Both sit under each panel and track it on its own, but a microinverter turns that panel’s power into AC on the roof, while a DC optimiser sends DC to one central inverter that does the conversion. That inverter can be a hybrid with a battery on its DC side; microinverters need a battery with its own inverter (AC coupled). AC vs DC coupled batteries
Can optimisers be added to an existing solar system?
Often, yes. Tigo says its TS4-A-O suits “new designs and existing systems” and is fully compatible with thousands of different inverter models from more than 50 inverter brands. An electrician first checks your inverter is on Tigo’s compatibility list, and its monitoring and rapid shutdown need a Tigo Access Point (TAP) and Cloud Connect Advanced (CCA). It is roof work, so it is worth doing alongside a service or another upgrade. Solar upgrades and servicing
How long do microinverters last?
The warranty is the best guide: Enphase warrants its IQ8 microinverters for 25 years from activation in Australia, if they are registered and connected to the internet within 45 days and stay connected. The makers warrant the Sungrow, Fronius and Alpha ESS models shown here for 5 to 10 years. Enphase’s warranty doesn’t cover the labour to swap a faulty unit.
Do I need microinverters for an east-west roof?
Not usually. In Mount Waverley, Melbourne, PVGIS puts a 6.6 kW array facing east at 87%, and facing west at 86%, of what it makes facing north over a year. East and west panels peak at different times, so each face goes on its own tracker, and the Sungrow, Fronius and Alpha ESS models shown here each have at least 2. Panel-level electronics help when shade or a third roof face comes into it. Which way panels should face
Shade and split roofs on Melbourne homes
Panels that don’t face north lose most in winter, when the sun is lowest and shadows are longest: in Mount Waverley, Melbourne, PVGIS puts east and west faces at only 63% and 64% of a north face’s June output. So the shade that matters is the winter-midday kind, from a tree, a chimney or a neighbour’s second storey while the sun sits low in the north. Where that crosses part of the array, microinverters or optimisers keep the unshaded panels at their best. Where the roof is simply split east and west, a tracker for each face on a string or hybrid inverter does the job, with no electronics on the roof.
We map your roof’s shade at the free inspection, then quote the set-up that suits it.
Get an inverter design for your roof
We look at your roof’s shade and faces at the free inspection, then quote the inverter that fits it.
Talk to us about a shaded roof
Locally owned, locally installed. Call, email, or send the form and we’ll come out and inspect the property.
- Phone
- 0485 000 015
- Workshop
- 8/41 Ricketts Road,
Mount Waverley, VIC 3149