A plug-in kit has solar panels, a small inverter that turns their DC power into 230 V AC, a mounting frame and a cable with a normal three-pin plug. Plugged into a wall socket, it feeds power into your home wiring, where running appliances use it first. Under the WA draft it must shut off within 100 milliseconds of being unplugged, and stop when the grid goes down.
On this page (10 sections)
- What is in a plug-in solar kit?
- What is a microinverter?
- What is the difference between VA and watts?
- Why are the panels allowed to be bigger than the inverter?
- Where does the power go once it is plugged in?
- Will I get paid for the surplus?
- What happens when I pull the plug out?
- What happens when the grid goes down?
- Does the inverter react to the grid in other ways?
- What about monitoring plugs and clamps?
A plug-in system is a small grid-connected solar system that skips the electrician and the switchboard. It works on the same basic idea as rooftop solar, at a much smaller size, and it reaches your wiring through a power point. This page describes how the draft WA standard expects kits to work. No kit is legal to use in WA yet.
What is in a plug-in solar kit?
The draft Technical Bridging Standard (clause 1) says a plug-in generator is made up of:
| Part | What it does |
|---|---|
| Solar panels (PV modules) | Turn sunlight into DC electricity. Usually one or two panels, per the FAQ. |
| Inverter | Converts the panels’ DC into 230 V AC that matches the grid. |
| Mounting system | Holds the panels on a balcony rail, wall, fence or the ground. The maker must supply it (clause 5.5.1). |
| Cable and plug | A sealed cable with a standard Australian Type I three-pin plug (AS/NZS 3112). |
| Battery (optional) | Stores solar power for later. It connects to the DC side of the same inverter. |
The inverter must also have a display or a phone app that shows its status and error messages, with guidance on what to do (clause 6.4.3).
The draft allows several layouts (clause 4.2.2). The simplest is one panel with the inverter built on. Others use two or more panels, an inverter with separate inputs for each panel, or a combined solar and battery unit where a DC controller handles battery charging. Apart from the simplest, which comes with its DC connections already made, you put it together using the maker’s own cables.
What is a microinverter?
“Microinverter” is the everyday name for the small inverters used in these kits. The draft calls it a “supplementary supply inverter”, rated for “one or a small number of PV modules or a battery storage module” (clause 3.1). The key word is supplementary: it “synchronises its output to the voltage and frequency of an existing supply and does not establish a supply of its own”. It can only push power in alongside the grid. It cannot run your home by itself.
What is the difference between VA and watts?
Watts (W) measure the power that does useful work, like heating a kettle. Volt-amperes (VA) measure “apparent power”, which the draft defines as RMS voltage multiplied by RMS current (clause 3.1). The two can differ for equipment that pulls current out of step with the voltage.
For small solar inverters the gap is small. The consultation paper says systems this size “are unlikely to generate much reactive power”. So in practice, my reading is that an 800 VA inverter puts out close to 800 W at most. That is why the government FAQ and announcement say “800 W” while the draft standard says 800 VA. The draft also caps current at 3.5 A, which is about what 800 VA works out to at 230 V.
Why are the panels allowed to be bigger than the inverter?
The draft allows up to 2,000 W of panels and battery on the DC side (clause 4.1), but only 800 VA out of the inverter. The inverter is the bottleneck for what goes into your wiring.
Panels rarely produce their full rated power. Their rating is measured under standard test conditions (clause 3.1, “Pmax”), and real output drops in the morning, the late afternoon, in heat and under cloud. My reading is that the extra panel allowance lets a kit reach its 800 VA limit for more of the day, and lets surplus DC power charge a battery. For what a kit might produce in Perth, see balcony solar output in Perth.
Where does the power go once it is plugged in?
Into your home wiring, through the socket. Electricity from the kit is used by whatever is running in your home at that moment, such as the fridge, router or TV. If your home is using more than the kit makes, the grid supplies the rest, so you buy less power. If your home is using less, the surplus flows out to the grid. Western Power describes the same thing for rooftop solar: it “sends unused power back into the grid”.
Will I get paid for the surplus?
Not for now. The FAQ says the meter upgrades needed to pay for exports “would likely be net-negative for consumers”, and that metering in embedded networks, like apartment blocks, is harder. The focus is on self-consumption. The FAQ also says you do not need a smart meter. A battery is the way to keep more of your own solar: it charges from surplus during the day and the inverter draws on it later. See cost and savings and plug-in solar batteries.
What happens when I pull the plug out?
The inverter has to shut off fast so the pins of the plug in your hand are not live. Under clause 6.2.3.3.3 of the draft:
- the inverter must disconnect from mains within 100 milliseconds
- the voltage at the plug pins must fall below 34 V within 100 milliseconds
- capacitors over 100 nF must discharge to 34 V or less within 1 second
The plug must also have extra protection in case the main protection fails: either a lock that stops the plug coming out without a tool until the output is off, or a separate electronic cut-out that removes dangerous voltage within 2 seconds (clause 6.2.3.2). The draft’s stated goal is “electrical safety like that of other appliances that users connect to a standard wall outlet.”
What happens when the grid goes down?
The kit stops. The inverter “must cease its output if grid supply ceases” (clause 6.2.3.2), and must pass the AS/NZS IEC 62116 anti-islanding test (clause 6.4.1). Anti-islanding stops the inverter from keeping a cut-off section of the network live, which protects line workers and anyone near a fallen wire.
That means a plug-in kit is not a backup power supply through the wall socket, even with a battery. The draft does not describe any blackout mode.
Does the inverter react to the grid in other ways?
Yes. It must meet the region B settings of AS/NZS 4777.2:2020 on Western Power’s network or region C on Horizon Power’s, with some clauses removed (clause 7). Volt-watt response stays in. My understanding is that this means the inverter turns its output down when local grid voltage runs high. The kit’s instructions must tell you how to set the right region (clause 8.3.1).
What about monitoring plugs and clamps?
Smart plugs and current clamps that help you match your usage to solar output are outside the standard. The draft says they must meet the existing testing and certification rules for those devices (clause 1).