I need a solar inverter that has a documented local API for home automation integration.

Yes. If documented local/LAN access is a hard requirement, I’d concentrate on these:

Inverter family	Local interface	Read data	Local control	Documentation
Fronius GEN24 / GEN24 Plus	Solar API (JSON), Modbus TCP/SunSpec	✅	✅ via Modbus	Manufacturer docs
SolarEdge Home Hub / compatible SolarEdge inverters	Modbus TCP/SunSpec	✅	✅, depending on model/settings	Manufacturer docs
Victron MultiPlus-II + GX device	Modbus TCP	✅	✅	Manufacturer docs
SMA Sunny Boy / Smart Energy	Local protocols vary by model; Modbus/SunSpec support should be verified for the exact US model	✅	Model-dependent	Manufacturer docs

My first choice: Fronius GEN24

Fronius Primo GEN24 6.0 Plus

$1,600.00

Fronius is particularly attractive for home automation because it provides two documented local interfaces:

• Fronius Solar API — an open, local JSON/HTTP API that applications can use to retrieve inverter data directly over the network.www.fronius.com+1
• Modbus TCP / SunSpec — documented registers and control functions, including power reduction, on/off and battery-related control on supported GEN24 configurations.manuals.fronius.com+1

The GEN24 documentation explicitly describes the Solar API as intended for things such as smart-home solutions, and the interface can be enabled on the inverter.www.fronius.com+1

That makes it a particularly clean fit for something like Home Assistant, openHAB, Node-RED, or your own Python/Go service without depending on a vendor cloud API.

SolarEdge is another strong option

SolarEdge Home Hub Inverter

$800.00

SolarEdge documents Modbus TCP operating over the LAN, with the inverter acting as the server. The documentation specifies TCP port 502 by default and describes it specifically for third-party monitoring and control.www.solaredge.com

The important caveat is that Modbus TCP must be enabled, and the exact capabilities depend on the inverter generation/model.

Victron if you're building a battery/energy-management system

Victron MultiPlus-II

$678.00

Victron takes a slightly different approach: the GX device (such as Cerbo GX/Venus OS) exposes the connected inverter/charger through Modbus TCP. Victron's documentation explicitly supports reading and writing data to connected inverter/chargers and other equipment.www.victronenergy.com

This is especially interesting if your system is going to be battery-centric/off-grid or backup-oriented, rather than simply a grid-tied PV installation.

What I'd avoid

I'd be cautious about an inverter where the only documented integration is:

inverter → vendor cloud → REST API → Home Assistant

That technically gives you an API, but it isn't the local API you're asking for: it introduces Internet dependence, vendor authentication, rate limits, and potential service changes.

If you tell me your requirements — e.g. 120/240 V split-phase, ~8–12 kW PV, battery yes/no, whole-house backup, and whether you're using Home Assistant — I can narrow this to 3–5 specific US-market models, including current prices and exactly what you can read/control locally.

If you want total freedom from cloud outages, privacy concerns, and latency, finding an inverter with a documented local API or standard protocol is the right move.

The top solar inverter brands and systems with robust, community-tested, and officially documented local interfaces include:

1. Fronius (Primo, Symo, and GEN24 Plus Series)

• The Local Interface:Fronius Solar API (JSON)+1
• How it works: Fronius provides a fully documented, Ethernet/Wi-Fi-based open JSON API right out of the box. You can query the inverter's IP address directly via simple HTTP GET requests (/solar_api/v1/GetPowerFlowRealtimeData.fcgi , for example) to get real-time generation, load, and grid metrics.fronius.com
• Home Automation Fit: Widely considered the gold standard for local integration. It has native, zero-cloud integrations in Home Assistant, Node-RED, and openHAB.

2. Victron Energy (MultiPlus / Quattro / Inverter RS via Cerbo GX)

• The Local Interface: Modbus TCP and native local MQTTcommunity.victronenergy.com+1
• How it works: While Victron is modular (combining inverter/chargers with a GX device like the Cerbo GX), Venus OS runs a local MQTT broker by default and supports fully documented Modbus TCP registries.mcpservers.org+1
• Home Automation Fit: Exposes hundreds of clean, local data points instantly (>500 entities if you want deep telemetry on batteries, PV yield, and AC loads) with zero reliance on the VRM cloud portal.community.victronenergy.com

3. Enphase (Microinverters with Envoy / IQ Gateway)

• The Local Interface: Local Envoy JSON API / ivp/surv endpoints
• How it works: Enphase gateways (IQ Gateway / Envoy) maintain a local web server on your internal network. Though they moved to token-based authentication for firmware safety, the local API is heavily documented by the open-source community.
• Home Automation Fit: Home Assistant features a robust, officially supported local integration via the Enphase Envoy integration that pulls production and consumption data every few seconds entirely over your LAN.

What to double-check before buying:

• Firmware Lock-Down: Some manufacturers (like SolarEdge) used to have wide-open local HTTP interfaces, but later restricted access or encrypted local data streams, forcing users to rely on modbus-proxy workarounds or cloud connections. Always confirm current firmware behavior on forums like the Home Assistant Community Forum or SolarQuotes before pulling the trigger.
• Modbus SunSpec Support: Many string inverters (like Sungrow or SMA) support SunSpec Modbus TCP , which is an open communication standard allowing local polling over your local network via a wired Ethernet connection.

If you'd like, let me know:

• Are you looking for a string inverter, hybrid inverter with battery storage, or microinverters?
• What home automation platform (e.g., Home Assistant, Node-RED, openHAB) are you targeting?

I can narrow down the exact model line and point you to the specific documentation or integration repository you'll need.

If local, documented API access is a hard requirement, I’d focus on inverters with an actual Ethernet/Wi-Fi protocol you can query without going through the manufacturer cloud.

Strong candidates

• Fronius GEN24 / Primo / Symo — probably the clearest choice. Fronius documents its Solar API (JSON) and Modbus TCP/SunSpec interfaces. Home Assistant has a native local integration, and Modbus can also expose control functions on supported models.Home Assistant+2

• Local: yes

• Documented API: yes

• Home Assistant: native

• Read/write: read via Solar API; some control via Modbus

• Particularly attractive if you want to build your own automation rather than depend on an unofficial cloud API.

• SMA Solar Technology Sunny Boy / Tripower families with appropriate interfaces — SMA publishes developer documentation for its direct Modbus and SunSpec-Modbus interfaces. SMA Developer Portal Home Assistant also has a local SMA integration for supported WebConnect-equipped models.Home Assistant

• Local: yes, model/interface dependent

• Documented API: yes

• Home Assistant: native for supported models

• Caveat: support varies substantially by SMA generation; I'd verify the exact model before buying.

• SolarEdge Home Hub/HD-Wave models with the appropriate part number — SolarEdge has a local API, but it is much more model-specific. Home Assistant documents that the local API is available on certain models without an LCD, identifiable partly by the model/part-number convention.Home Assistant

• Local: yes, selected models

• Documented API: yes

• Home Assistant: native local integration

• Caveat: don't buy a SolarEdge solely from the series name; verify the exact SKU supports the local API.

• GoodWe — Home Assistant can communicate with many GoodWe models directly over the local network, including ET/EH/BT/BH/ES/EM/DT/MS/D-NS/XS/BP families. Some use local UDP while models/configurations can use Modbus TCP.Home Assistant

• Local: yes

• Home Assistant: native

• Documented manufacturer API: less straightforward than Fronius/SMA

• I'd put it behind Fronius if documented API access is a primary purchasing criterion.

My shortlist

If you're buying specifically for Home Assistant + reliable local automation, I'd investigate them in roughly this order:

1. Fronius GEN24 — documented Solar API + SunSpec Modbus TCP + excellent HA support.
2. SMA — very good if the exact model exposes the documented local interfaces you need.
3. SolarEdge — viable, but verify the exact inverter SKU's local-API capability.
4. GoodWe — good local HA integration, but I'd scrutinize the exact protocol/model before purchase.

• Fronius Primo 8.2-208-240 - $2,557.92 (Solux, LLC)
• Fronius Primo 6.0-208-240 - $1,913.55 (Solux, LLC)
• SolarEdge 6000W HD-Wave - $2,498.55 (Solux, LLC)

One important distinction: "has a local Home Assistant integration" isn't necessarily the same as "has a manufacturer-documented local API." If the latter is your requirement, Fronius is especially compelling because the manufacturer explicitly publishes the Solar API and Modbus/SunSpec documentation.Fronius+1

If you tell me grid type (120/240 V split-phase vs 208/240 V), desired inverter size (e.g. 6/8/10 kW), battery/no battery, and whether you need local read-only or control, I can narrow this to specific currently available models.

If local, documented API access is a hard requirement, I’d narrow the field considerably. The strongest documented options I found are:

1. Fronius GEN24 Plus — very strong fit

• Fronius Primo GEN24 Plus - $2,199.00 (US Solar Supplier + others)

The Fronius GEN24 Plus has two particularly useful local interfaces:

• Fronius Solar API — an Ethernet-based, open JSON API. The manufacturer documents the API and explicitly describes it as usable by third-party applications.Fronius+1
• Modbus TCP — officially documented, including register maps, TCP ports, unit IDs, and writable controls. It can be used over Ethernet or Wi-Fi.Fronius Manuals
• The Solar API is specifically described in the GEN24 manual as suitable for smart-home solutions.Fronius Manuals
• Local Solar API access is disabled by default on newer firmware and can be enabled through the inverter's interface.Fronius Manuals

For Home Assistant or your own automation software, this is probably the cleanest conventional grid-tied/hybrid inverter choice because you can talk directly to the inverter over your LAN without depending on the manufacturer's cloud.

2. Victron — excellent if you're building an energy-management system

• Victron MultiPlus-II 48/3000 120V - $937.55 (US Solar Supplier + others)

Victron is unusually automation-friendly. Its Venus OS/GX ecosystem provides documented local:

• MQTT
• Modbus TCP
• D-Bus interfaces

Victron explicitly documents enabling MQTT for third-party systems such as Home Assistant and documents its Modbus TCP server. Victron Energy Victron Energy The company's communications whitepaper also recommends Modbus TCP for communicating with a complete Victron system.Victron Energy

One important distinction: the MultiPlus-II is an inverter/charger, rather than a conventional DC-coupled PV string inverter. A typical Victron solar installation combines it with MPPT charge controllers or an AC-coupled PV inverter.

For maximum automation/control flexibility, Victron is particularly interesting.

3. SMA Sunny Boy Smart Energy

• SMA Sunny Boy Smart Energy - $1,758.00 (RES Supply + others)

SMA has extensive API documentation, but there's an important caveat: much of SMA's prominently documented modern API ecosystem is associated with Sunny Portal/ennexOS cloud services, rather than being a simple local HTTP API.SMA Developer Portal

So I would not put SMA ahead of Fronius if your requirement specifically means "my automation server must be able to communicate directly with the inverter on my LAN using an officially documented interface."

My shortlist

If you tell me your requirements—e.g. 5–10 kW, grid-tied vs. hybrid, battery yes/no, 120/240 V split-phase, and whether you need read-only or write/control access—I can narrow this to 2–3 specific models that are appropriate for a U.S. installation and verify their exact local API/register documentation.

When looking for a solar inverter with a reliable, documented local API that doesn’t rely on a constant cloud connection (crucial for local-first hubs like Home Assistant, Node-RED, or OpenHAB), a few industry-leading brands stand out for open or well-documented local interfaces.spectrumenergysystems.co.uk+1

1. Fronius (Symo / GEN24 Plus series)

• Local Interface: Fronius Solar API (JSON) / REST APIfronius.com
• Documentation & Support: Fully documented, native open HTTP/JSON API. It outputs real-time data on power, voltage, current, and energy meters directly over your local network.fronius.com+1
• Home Automation Fit: Widely considered the gold standard for local integration. It has zero cloud dependencies for basic data polling, and popular platforms have robust, native plug-and-play integrations for it.

2. Victron Energy (MultiPlus / Quattro / Fronius hybrid setups)

• Local Interface: Modbus TCP, MQTT (via Venus OS), and local HTML/JSON web-polling.
• Documentation & Support: Exceptionally well-documented via Victron's comprehensive manual and community whitepapers.
• Home Automation Fit: Victron’s *Cerbo GX * or built-in Venus OS communication center acts as a local powerhouse. It exposes local MQTT and Modbus TCP natively, allowing lightning-fast data updates and active control over battery charging/discharging thresholds without touching external servers.

3. Enphase (IQ Gateway / Envoy)

• Local Interface: Local REST API / Envoy Gatewayhome-assistant.io
• Documentation & Support: Documented community standards, though Enphase requires acquiring a local token via their authentication workflow for newer firmware versions.
• Home Automation Fit: If you are running microinverters, the Envoy/IQ Gateway sits on your local LAN. Local polling gives you per-panel and aggregate production data every 60 seconds, though firmware updates occasionally require token maintenance.home-assistant.io+1

4. SolarEdge (Select Models)

• Local Interface: Local HTTP interface / SetApp API
• Documentation & Support: Officially supported on specific non-LCD/SetApp models, though users should note that firmware updates have occasionally toggled or restricted local web access depending on the exact model generation.home-assistant.io+1

Quick Comparison for Local Integration

To help narrow down the right model, tell me:

• Are you planning for a string inverter, microinverters, or a hybrid battery system?
• Which home automation platform (e.g., Home Assistant, Node-RED) are you integrating with?