Accessories
Accessories are the metering, communication and connection components that turn a set of panels and an inverter into a controlled, monitored photovoltaic system. Choose by function: smart meters for export limiting and self-consumption, in single-phase or three-phase versions, Wi-Fi and LAN modules for cloud monitoring, optimisers from SolarEdge and Tigo for shaded roofs, monitoring hardware, solar heating diverters and MC4 connectors. Accessories from AEG, Acrel, Eastron, Fronius, Goodwe, Huawei, Marstek, SolarEdge, Solis, Solplanet, Soluna, Tigo and Victron Energy. Guide
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Choose accessories according to brand
LAN or Wi-fi modules
These connect your voltage converter to a cloud server, guaranteeing software updates and data transfer so you can manage your solar system clearly and control the return on your green energy investment.
Smart meters
Smart meters are used to manage the flow of energy and are smart meters. You will primarily use them to monitor and control energy production. This way, you have control over any unwanted flows into the grid.
With a smart meter, you can control precisely how much energy you consume from your solar panels and how much from the grid. It can also monitor the export of power back to the grid.
Optimizers
In the context of photovoltaics, a power optimizer is an electronic device that is used to optimize the performance of photovoltaic panels in solar systems. Its main objective is to increase the overall efficiency and performance of the solar system by minimizing energy losses caused by various factors such as shading, irregular lighting, or adverse conditions on the panels.
Monitoring
A monitoring device tracks the performance of a solar power system by measuring parameters like energy production, voltage, current, and efficiency. It helps detect faults, optimize performance, and ensure reliability.
Solar Heating
A solar heating device captures and converts sunlight into thermal energy to heat water or air for residential, commercial, or industrial use. It typically includes solar collectors, a heat transfer system, and storage.
Connectors
Includes essential components for linking solar panels, inverters, and other system parts. These connectors ensure secure, efficient, and weather-resistant electrical connections, minimizing power loss and enhancing system reliability.
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Photovoltaic accessories: metering, communication and connection
Three groups of accessories decide how a system behaves once it is energised. Smart meters sit at the grid connection point and tell the inverter what is flowing in and out, which is what makes export limiting and self-consumption control possible. Communication modules (Wi-Fi, LAN, RS485 or 4G) carry that data to the manufacturer's portal for monitoring, firmware updates and remote diagnostics. Optimisers and module-level electronics recover the yield that shading and mismatch take away.
The rest is the physical layer: MC4 and MC4-EVO2 connectors, crimping tools and DC cable that hold the string together for twenty-five years. This category stocks accessories from Acrel, AEG, Eastron, Fronius, Goodwe, Huawei, Marstek, SolarEdge, Solis, Solplanet, Soluna, Tigo and Victron Energy. Always match the accessory to the inverter brand first, because most meters and dongles are only released for their own ecosystem.
FROM THE FIELD
"Most self-consumption complaints we troubleshoot are not inverter faults, they are meter installation faults. The meter has to sit at the main incomer, upstream of every load and of the inverter feed-in point, with the current transformers facing the right way and each CT on the phase its voltage terminal is wired to. Get one CT reversed and the system will happily export while the battery sits idle."
Ladislav Proc · Photovoltaics specialist, ONSA Plus
How to choose photovoltaic accessories
Accessories are not interchangeable between brands. A meter, a dongle or an optimiser has to be on the inverter manufacturer's compatibility list, otherwise the inverter will either refuse to pair with it or read it incorrectly. Start from the inverter you have chosen, then work outwards.
Decide in this order: do you need a meter (almost always yes if there is a battery, a grid limit or any self-consumption logic), how the inverter will get online, whether the roof justifies module-level electronics, and finally the connectors and DC cabling that tie it together.
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Smart meters: why the inverter needs one
A smart meter is a bidirectional energy meter installed at the grid connection point and wired to the inverter over RS485 / Modbus RTU. The inverter reads the direction and size of the flow several times a second and adjusts its own output accordingly. Without it the inverter is blind: it cannot tell the difference between energy going into the house and energy going into the grid.
- Export limiting (zero export): where the distribution operator caps or forbids feed-in, the meter is what lets the inverter throttle its AC output to stay within the limit.
- Self-consumption and battery control: the meter tells the hybrid inverter when there is surplus to store and when the house is drawing from the grid, so the battery charges and discharges at the right moments.
- Consumption monitoring: without a meter the portal shows production only. With one it shows house load, import, export and self-consumption ratio.
- Surplus diversion: hot water diverters and load control outputs need the same measurement to decide when there is spare energy.
Single-phase or three-phase, direct or CT
The meter must match the connection, not the inverter. A single-phase meter measures one live conductor and suits single-phase supplies. A three-phase meter measures all three and is what you need on a three-phase supply, even if the inverter itself is single-phase, because otherwise the system only sees a third of the household load.
- Direct connection: the main conductors pass through the meter itself. Simple, no external transformers, but limited to smaller main breakers, typically up to around 63 A or 80 A depending on the model.
- CT (current transformer) connection: split-core or solid-core clamps go around each phase conductor and only the small secondary wiring runs to the meter. Required for larger services and much easier to retrofit in a live board.
- CT ratio matters: the ratio programmed into the meter must match the transformer fitted, or every reading is wrong by that factor.
- Direction and phase mapping: the arrow on each CT points towards the load, and CT number one has to be on the same phase as voltage input L1.
Tip from practice
Run the meter's RS485 pair in shielded twisted-pair cable, keep it out of the same conduit as AC power cables, and terminate the bus properly. A long unshielded data run next to a 3-phase supply is the classic cause of intermittent "meter not found" errors that look like a faulty meter but are not.
Wi-Fi, LAN and monitoring dongles
The communication module connects the inverter to the manufacturer's portal. That link is what delivers firmware updates, remote parameter changes, fault alerts and the production history a warranty claim needs. Modules are brand-specific: a Huawei dongle will not work in a Solis inverter.
- Wi-Fi: quickest to commission, but most dongles are 2.4 GHz only and a plant room or metal enclosure kills the signal. Check coverage at the inverter, not at the router.
- LAN: the reliable choice for anything you plan to monitor seriously, and for sites where remote control by the network operator is a connection condition.
- 4G: for ground mounts and buildings with no usable network. Needs a SIM and a data plan.
- Data loggers: larger sites chain several inverters over RS485 into one logger, which is also where a plant-level meter is usually read.
Optimisers: when module-level electronics pay off
An optimiser is a DC-DC converter fitted to each module. It performs MPPT at module level, so a shaded or soiled panel no longer drags the whole string down to its own current, and it reports per-module data. It also provides module-level rapid shutdown, dropping the DC voltage to a safe level when the inverter stops.
- SolarEdge: a complete architecture. Optimisers are mandatory on every module and only work with a SolarEdge inverter, which runs at a fixed string voltage. Module-level monitoring and SafeDC come as standard.
- Tigo: selective deployment. Fit TS4 units only to the modules that are actually shaded, on almost any string inverter, including retrofits. Monitoring needs the matching Tigo gateway.
- Worth it when: chimneys, dormers, trees or masts shade part of the array; one string mixes orientations or tilts; you need per-module fault finding on a large roof; or a local rule requires module-level shutdown.
- Not worth it when: a clear, uniform, single-orientation roof. Extra components on the roof mean extra connections and extra failure points for no measurable gain. Splitting the array over two MPPT inputs is often the better answer.
Solar heating: putting surplus into hot water
A PV surplus diverter watches the meter reading and modulates power into the immersion heater in the hot water cylinder, so that the export stays near zero instead of energy leaving at a low feed-in rate. Because it varies the power continuously rather than switching a fixed load on and off, it can use a few hundred watts of surplus as readily as three kilowatts. It is the cheapest form of storage available: no chemistry, no cycle life, but the energy comes back as heat only.
MC4, EVO2 and crimping
DC connectors are the most common cause of DC-side faults and roof fires. A poor crimp adds contact resistance, resistance makes heat, heat degrades the contact further and the process runs away.
- Match the system: MC4 and MC4-EVO2 are different families. Mating connectors from different manufacturers is not covered by IEC 62852 type approval, even when they physically click together.
- Crimp, do not solder: use the crimping tool with the correct die for the contact and the conductor cross-section, usually 4 mm² or 6 mm² solar cable. Pull-test the first crimp of every batch.
- Tighten the gland: the IP67 or IP68 rating only exists once the cable gland is torqued down onto the correct cable diameter.
- Use the spanner: unmate with the proper key, never by pulling the cable, and keep spare connectors on the van so a damaged one gets replaced rather than reused.
Which accessory does what
| Accessory | What it does | When you need it |
|---|---|---|
| Smart meter | Measures import and export at the connection point over RS485 | Battery systems, export limits, self-consumption and load control |
| Wi-Fi or LAN module | Links the inverter to the manufacturer's cloud portal | Every installation: updates, alerts, diagnostics, warranty evidence |
| Optimiser | Module-level MPPT, per-module data and safe DC shutdown | Shaded roofs, mixed orientations, module-level shutdown rules |
| Solar heating diverter | Modulates surplus power into an immersion heater | Low feed-in value and a hot water cylinder already in place |
| MC4 and EVO2 connectors | Weatherproof DC connection rated to 1500 V DC | Every string: extensions, repairs, re-terminations |
Swipe the table to the left
Frequently asked questions about photovoltaic accessories
Why does my inverter need a smart meter?
Because the inverter cannot otherwise tell whether energy is going into the house or into the grid. The meter measures at the connection point and reports over RS485, which is what enables export limiting, battery charging from surplus and consumption monitoring in the portal.
Do I need a three-phase meter if my inverter is single-phase?
Yes, if the house supply is three-phase. The meter has to see the whole connection point, so on a three-phase supply fit a three-phase meter. A single-phase meter would only measure one phase and the system would misread household consumption.
What is the difference between a direct-connection and a CT smart meter?
A direct meter carries the main conductors through the meter itself and suits smaller main breakers, typically up to around 63 A or 80 A. A CT meter uses current transformers clamped around each phase, so it handles larger services and is far easier to retrofit.
Where should the smart meter be installed?
At the main incomer, upstream of every load and of the point where the inverter feeds in, so it sees the complete exchange with the grid. Each current transformer must face the load and sit on the phase matching its voltage terminal.
Can I use any Wi-Fi dongle with my inverter?
No. Communication modules are brand-specific and often model-specific, so a Huawei dongle will not pair with a Solis or Fronius inverter. Order the module released for your inverter family and check whether it needs the inverter firmware to be updated first.
Is LAN better than Wi-Fi for inverter monitoring?
Yes, where a cable can be run. Most dongles only support 2.4 GHz Wi-Fi and plant rooms, basements and metal enclosures weaken the signal badly. LAN gives a stable link for firmware updates, alerts and any remote control required by the network operator.
When are optimisers worth the extra cost?
When part of the array is shaded by chimneys, dormers or trees, when one string mixes orientations or tilts, when you want per-module fault finding, or when module-level rapid shutdown is required. On a clear, uniform, single-orientation roof they add cost and connections for little gain.
What is the difference between SolarEdge and Tigo optimisers?
SolarEdge is a full architecture: an optimiser on every module and a matching SolarEdge inverter. Tigo units are selective, so you fit them only to the affected modules and keep almost any string inverter, which also makes them suitable for retrofits.
How does PV surplus water heating work?
A diverter reads the meter at the connection point and modulates power into the immersion heater in the cylinder, holding export near zero. Because the power is varied continuously, it uses small surpluses as well as large ones. The energy is recovered as heat only.
Can I mix MC4 connectors from different manufacturers?
No. Cross-mated connectors are outside IEC 62852 type approval even when they click together, and the contact geometry may differ enough to cause heating. Use one family throughout, crimp with the correct die for the 4 mm² or 6 mm² cable, and tighten the gland.
Compatibility of meters, communication modules and optimisers depends on the specific inverter model and firmware version.
About ONSA Plus
Why installers across Europe order accessories from us
ONSA Plus is a European B2B distributor of photovoltaics, battery storage, heat pumps and EV charging stations. In our own EU warehouses we keep over 1,500 products from 25+ brands, including Huawei, Solis, SolaX and Dyness.
We are not just a trading company. We design and service energy systems ourselves, so we answer questions on meter wiring, monitoring and module-level electronics from engineering practice, not from a catalogue. You handle a warranty claim directly with us and you buy per job.
