Review of the Hoymiles HiOne-20T-G3 – All-in-One BESS for Discerning Homeowners

The Hoymiles HiOne-20T-G3 review shows what Hoymiles is aiming to achieve with its G3 generation: combining an inverter, battery, and energy management system into a single, modularly expandable integrated system—with the V2X module serving as a standalone component—all with a rated output of 20 kW for three-phase operation. We took a close look at the system, including a HiOne-8B-G3 battery, the Electric Energy Meter, and the Data Transfer Stick, and show what the storage system is really capable of in everyday use.

Technical Specifications & Package Contents

Component	Model	Value
Inverter	HiOne-20T-G3	20 kW rated power (three-phase)
Battery type	HiOne-8B-G3	LiFePO₄, 314 Ah cells
Usable capacity	HiOne-8B-G3	7.8 kWh (DoD 100%)
Max. charging/discharging power WR	HiOne-20T-G3	20,000 / 21,000 W
Max. PV input power	HiOne-20T-G3	40,000 W (DC/AC ratio up to 200%)
Peak efficiency	HiOne-20T-G3	98.5%
EU efficiency	HiOne-20T-G3	98.0%
Cycle life	HiOne-8B-G3	8,000 cycles at 25 °C / 0.5C
Protection class	Both	IP66
Operating temperature	WR	−30 to +65 °C (>45 °C: derating)
Dimensions WR	HiOne-20T-G3	620 × 360 × 255 mm
Weight WR	HiOne-20T-G3	31 kg
Battery weight	HiOne-8B-G3	67 kg
WR Communication	HiOne-20T-G3	RS485, Bluetooth, Wi-Fi/Ethernet (optional)
Battery warranty	HiOne-8B-G3	10 years
Certification	System	TÜV-certified

The system comes in three shipping boxes: the inverter module with the DTS-WL-G3 data transfer stick and energy meter in one package, and the base and top plates in the second. The battery module is shipped separately—safely packed in a wooden crate that also allows for transport via a pallet jack. All components are carefully padded with foam.

Design & Workmanship

The HiOne system immediately stands out thanks to its well-thought-out modular design. The inverter module and battery share the same enclosure dimensions (620 × 360 × 255 mm)—all modules can be stacked to form a visually cohesive unit that looks great even in high-profile spaces. and optional V2X module

The body is primarily made of metal, while the cover and side panels are made of plastic. The build quality is high overall, though upon close inspection, some plastic parts do not fit perfectly flush—this is not noticeable at a glance. The top section with its integrated LED display looks elegant, but it’s highly reflective and shows fingerprints quickly. You’ll want to keep a microfiber cloth handy.

The device itself features six status indicators: three error LEDs for smart meter connection, power supply/fuses, and network/cloud, as well as three value displays for solar yield, battery SOC, and current household consumption. This provides a quick overview without having to open the app.

The battery module weighs 67 kg—the wall mount or freestanding base must be installed by two people during transport. The connectors are designed as quick-connect types, which significantly reduces installation time. According to the manufacturer, the HiOne module itself can be installed in about 15 minutes; in practice, the total time required, including cabling and PV connection, is around four hours.

Field Test: Performance and Energy Management

Inverter: 20 kW with 98.5% efficiency

The HiOne-20T-G3 is the most powerful three-phase inverter in the HiOne-G3 series and is designed for larger single-family homes as well as small commercial properties with high self-consumption. With a recommended PV input power of up to 40,000 Wp and a DC/AC ratio of up to 200%, even significantly oversized PV systems can be managed with a single unit.

Four independent MPPT inputs (each with up to 20 A input current, voltage range 150–950 V) allow the modules to be oriented in different directions without risking losses due to shading on other strings.

The peak efficiency is 98.5%, and the EU efficiency is 98%. This is on par with other premium hybrid inverters. In everyday use, the device operates very quietly—the fan barely kicks in with a moderate PV system (5–6 kWp). At full load of 20 kW, the situation is likely to be different.

Battery: LiFePO₄ with 8,000 cycles—real-world performance confirmed

The HiOne-8B-G3 uses LiFePO₄ cells with a capacity of 314 Ah. Total energy capacity: 8.04 kWh; 7.8 kWh is available for use after internal DC-DC conversion (DoD 100%).

In a real-world test conducted from March through June 2026, a 7.05-kWp system generated approximately 2.62 MWh of electricity. Of this, about 172.9 kWh was stored—and 166.4 kWh was subsequently drawn from the storage system. This corresponds to a charge cycle efficiency of approximately 96%, which is in line with the specifications in the data sheet.

The maximum charging power of 4 kW (with a single battery pack) was consistently achieved during the test. A full charge takes about 2.5 hours under good sunlight conditions.

8,000 cycles at 25 °C correspond to a service life of just over 22 years with daily operation. LiFePO₄ is also considered the safest lithium chemistry and is not prone to thermal runaway—a decisive advantage for outdoor installation. Hoymiles offers a 10-year warranty on the battery and has had the system TÜV-certified. The 6-step battery safety concept includes, among other things, thermal sensors, automatic shutdown in case of overheating, and an integrated fire suppression system (aerosol).

If capacity needs to be increased, up to four HiOne-8B-G3 modules can be stacked—resulting in a total capacity of 32.16 kWh. Two units connected in parallel provide up to 64 kWh. A particularly practical feature: The system allows for the mixing of new and previously used battery modules. An integrated self-heating system also improves performance at temperatures below 0 °C.

Additional performance ranges

The 6 operating modes and off-grid operation

The HiOne system offers six operating modes for grid-connected operation as well as an off-grid mode:

• Self-Consumption Mode: PV first supplies the loads; excess electricity charges the battery; the remainder feeds into the grid. The grid does not charge the battery (except when the SOC is very low).
• Economy Mode: The storage system takes advantage of dynamic rates—it charges during off-peak hours and discharges during peak hours. Ideal for variable electricity contracts.
• Backup Mode: Keeps the battery at a high charge level at all times to prepare for frequent power outages. This consumes more grid power than Self-Consumption Mode.
• Peak Shaving Mode: Cuts off consumption peaks—relevant for small businesses with power-based grid fees.
• Time of Use Mode: Freely configurable charging and discharging times tailored to your individual electricity rate plan.
• AI Mode: Based on a proprietary AI algorithm, the system analyzes electricity prices, weather forecasts, and the household’s individual consumption habits—and automatically optimizes the charging and discharging strategy for the next 24 hours.
• Off-Grid Mode: Operates completely off-grid, combined with a generator or a large PV system.

Emergency Power Operation and Gateway

In off-grid mode, the HiOne-20T-G3 delivers up to 30,000 VA of apparent power as a peak load (10 seconds)—though this is only achievable in combination with the optional HiBox-63T-G3 gateway. The gateway switches over in 0 ms in the event of a grid outage, ensuring that no critical loads are interrupted, even briefly. Without the gateway, only limited backup is possible.

Electric Energy Meter (Meter-G3)

The Meter-G3 included in the scope of delivery is a DIN-rail-mounted meter with an external current clamp (120 A/40 mA CT). It measures voltage, current, and active power with ±0.5% accuracy and transmits the data to the inverter via RS485/Modbus RTU every 100 ms. This forms the basis for zero-feed-in and precise export management. We noticed, however, that the Smart Meter switches more slowly than a wirelessly connected Anker Solix Smart Meter.

Data Transfer Stick (DTS-G3)

The Data Transfer Stick plugs directly into the inverter via USB. It comes in three versions:

• DTS-WL-G3 (included): Wi-Fi (IEEE 802.11ax) and LAN (10/100 Mbps, max. 100 m), 105 g
• DTS-4G-G3 (alternative): Wi-Fi + 4G (LTE-FDD/LTE-TDD, incl. 3G/2G fallback), compact design (103 g)
• DTS-WiFi-G3 (alternative): Wi-Fi only, most compact design (82 g)

All three use Bluetooth 5.0 for local app configuration and upload data to the S-Miles Cloud every 30 to 600 seconds. In testing, the DTS was connected via LAN—this noticeably improves connection stability.

Software & App (S-Miles Cloud)

The S-Miles Cloud app for iOS and Android displays generation, consumption, battery charge level, and grid draw in a clearly structured, real-time format. Individual module monitoring (for existing microinverters) and MPPT analysis are integrated. Firmware updates are prominently displayed when the app launches and can be initiated directly.

Important for buyers: Commissioning of the HiOne system is reserved exclusively for registered Hoymiles installers. End customers cannot commission the system themselves. This prevents misconfigurations and ensures that the installer sets the parameters correctly.

During testing, a firmware error occurred shortly after commissioning: When the battery was fully charged, the inverter stopped supplying power and had to be restarted manually. It took Hoymiles a little while to find the error, but they were ultimately able to fix it via a firmware update.

Positive: The app displays the individual output of each PV string (PV1–PV4) as soon as you tap the solar display—an unusually high level of transparency for an end-user interface. Also accessible directly in end-user mode: heat pump control via the potential-free contact. Threshold values, time windows, and power limits can be set in the app without having to switch to the installer menu.

Another practical AI feature: The system automatically detects incorrectly connected CT terminals during the self-test and suggests the correct wiring. This saves the electrician from having to do rework.

Minor shortcomings of the app: No self-sufficiency indicator in the statistics view (only on the dashboard), no horizontal scrolling in bar charts, and the address can only be entered via a map pin.

The web portal complements the app well: It offers a heat map of daily yield, CSV data export, and nearly the same range of features—though the self-sufficiency analysis is completely missing here as well.

Overall, the app could be a bit more modern and respond a little faster.

Smart Home Integration via Modbus TCP

Hoymiles supports Modbus TCP for the HiOne, which enables direct local integration into energy management systems—including real-time data retrieval and rapid response for dynamic electricity rates or custom surplus management. An official Home Assistant integration was not yet available at the time of testing, but it can be set up manually via Modbus TCP.

A practical side effect for existing systems: If the Energy Meter detects power being fed into the grid (e.g., from existing third-party inverters), the HiOne also charges from the AC side. Excess energy from other inverters is thus automatically stored in the HiOne—significantly simplifying retrofitting for existing PV systems.

The Entire HiOne G3 Ecosystem: An Overview of All Variants

The HiOne-G3 system is deliberately designed to be modular. Those looking to configure the right setup have a wide range of options:

Three-phase inverters (HiOne-T-G3): The series ranges from the 8-kW model (HiOne-8T-G3) through 10 kW, 12 kW, and 16 kW to the 20-kW model tested here, the HiOne-20T-G3. All share the same design—cooling (natural convection up to 12 kW, active cooling starting at 16 kW) and the number of MPPT trackers (3 or 4) vary depending on the power class.

Single-phase inverters (HiOne-S-G3): For single-family homes with a single-phase grid, Hoymiles offers seven models ranging from 3.6 kW to 12 kW (HiOne-3.6S-G3 to HiOne-12S-G3). Same design, same battery compatibility.

HiOne-8B-G3 Battery: The universal battery model for all inverters in the series. By stacking (up to 4 modules) and connecting in parallel (up to 2 units), configurations ranging from 8 kWh to 64 kWh are possible.

V2X Module HiOne-22VD-G3: 22 kW bidirectional DC charger for Vehicle-to-Home and Vehicle-to-Grid. Interface: CCS1/CCS2, vehicle voltage: 200–1000 Vdc. Currently listed as a preliminary product. Important: The module is not an attachment to the tower but a flexible, externally mounted device —the distance from the tower can be freely selected, which is particularly relevant for garages located a considerable distance from the utility room. As a DC-to-DC charger, it eliminates the need for double voltage conversion (PV → AC → DC into the car), which improves charging efficiency compared to AC wallboxes.

Gateway HiBox-63T-G3 / HiBox-100S-G3: Three-phase (63 A) or single-phase (100 A) gateway for true whole-home backup with 0 ms switchover time. Up to two inverters can be connected in parallel to the HiBox-63T-G3—resulting in up to 40 kW of backup power. A generator connection is also provided (e.g., for prolonged power outages). There is a dedicated connection for § 14a-compliant controllable loads (e.g., heat pump, wallbox). For those who wish to combine multiple HiOne systems: Up to 10 units can be connected in a master-slave configuration.

Conclusion

The Hoymiles HiOne-20T-G3 with HiOne-8B-G3 is a well-designed all-in-one storage system that revealed no significant weaknesses in testing. Installation, load response, and battery performance are on par with what the specifications promise—which is not always a given in everyday use.

The key differentiating feature is its consistent openness: Modbus TCP for local smart-home integration, AC coupling for existing systems, and a modular design scalable up to 64 kWh. The V2X module was still missing at the time of testing, but anyone planning today will find that the HiOne system offers a platform with a clear path for future development.

Homeowners with a PV system between 15 and 40 kWp, a three-phase grid, and a need for future-proofing will find one of the most compelling options on the market here. The 8,000 charge cycles of the LiFePO₄ cells ensure a lower LCOE than systems with shorter lifespans—a factor that is often underestimated when considering total costs.

Two notes for purchase planning: If you need full-home backup, you’ll need to factor in the HiBox gateway as well. And there are no official list prices—the final price depends on the configuration and the installation company. Commissioning by a certified specialist company (e.g., PVSelected GmbH or Tepto GmbH) is mandatory in any case.