The Fox ESS KH8 (Part No. FE-KH1-8.0) is an 8 kW single-phase hybrid solar inverter from the Fox ESS K-Series — sitting directly above the KH7 in the range and offering an extra kilowatt of continuous output alongside a larger 16 kWp maximum array capacity and 12 kW peak PV input power. Like the rest of the K-Series, it features three independent MPPT trackers each spanning 80–500 V, giving installers the flexibility to handle split-orientation or partially shaded arrays without the yield losses associated with shared-tracker designs. The KH8 is fully compatible with the Fox ESS high-voltage lithium-ion battery range — ECS, HV2600, MIRA HV25 and EP series — supporting up to seven modules in series for a maximum storage capacity of 33.24 kWh. Its integrated EPS (Emergency Power Supply) switches to battery backup in under 6 milliseconds, delivering the full 8 kVA continuously with a 14.5 kW, 60-second surge to cover motor start-up loads. The fanless natural-cooling design keeps audible noise below 30 dB, the IP65 housing permits indoor or outdoor wall mounting, and FoxCloud V2.0 provides real-time generation, storage and consumption data via smartphone app or web portal from the included WiFi dongle. G99-certified for UK grid connection and MCS-compatible for Smart Export Guarantee registration.
⚠️ Installer Requirement — MCS Certification & Electrical Qualification
The Fox ESS KH8 must be installed by a competent, appropriately qualified electrical installer. UK grid-connected solar PV installations must be carried out by an MCS-certified installer to comply with G99 and to qualify for Smart Export Guarantee (SEG) payments. All AC wiring must meet BS 7671 (18th Edition IET Wiring Regulations). The KH8 is certified to G99 / EN50549, confirming compliance with UK and European grid-connection standards. Where the KH8 is replacing an existing string inverter, the full installation must be reassessed and re-notified as applicable under G99.
⚡ Important: DC-Coupled Hybrid — Replaces Your Existing Inverter
The KH8 is a DC-coupled hybrid inverter: it connects directly to solar PV strings via its three MPPT inputs and acts as the system's sole inverter. It replaces any existing string inverter and is not an AC-coupled add-on for retrofitting battery storage alongside a working inverter. For that application, the Fox ESS KA8 (AC Coupled version) is the appropriate alternative. The KH8 requires a CT clamp (supplied in box) for grid import/export monitoring; a Modbus energy meter (optional accessory) is recommended when the cable run from inverter to grid supply exceeds 30 metres. A second CT clamp is required if an additional generation source — such as a wind turbine — is also connected to the installation.
☀️ SEG Export Payments, FoxCloud V2.0 Monitoring & Parallel Scalability
Installed by an MCS-certified engineer and registered on the MCS database, the KH8 qualifies for Smart Export Guarantee (SEG) payments on surplus electricity exported to the grid. FoxCloud V2.0 delivers live and historical data on PV generation, battery state of charge, grid import/export and household self-consumption — via the Fox ESS smartphone app or browser dashboard. The WiFi dongle is included; optional 4G and LAN connectivity dongles are available for sites with poor WiFi coverage. For demanding loads, the KH8 supports parallel operation of up to ten units.
Key Features & Engineering Detail
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Three Independent MPPTs — 16 kWp Capacity, Complex Roofs Welcome
Three separate MPPT trackers, each rated to 16 A input current and spanning 80–500 V, allow the KH8 to accept up to 16,000 Wp of panel capacity across strings on different roof pitches, orientations or with independent shading profiles. Each string is tracked and optimised independently — preventing a poorly performing string from dragging down the yield of the others, which is a common limitation of single-tracker or dual-tracker designs.
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High-Voltage Battery Bus — 98.5% Charge Efficiency
Operating at a recommended battery bus voltage of 300 V (range 85–480 V), the KH8's high-voltage architecture minimises resistive losses across the charge and discharge cycle. PV-to-battery charge efficiency reaches 98.5% and battery-to-AC discharge efficiency is 97% — meaning the vast majority of every solar unit captured is actually delivered as usable power. Compatible batteries include the Fox ESS ECS, HV2600, MIRA HV25 and EP series, expandable to seven modules and up to 33.24 kWh.
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8 kVA EPS with 14.5 kW Surge — Full Power Backup, No Derating
The KH8's built-in Emergency Power Supply (EPS) detects grid loss and switches to battery supply in under 6 milliseconds — fast enough to maintain most sensitive loads without disruption. Unlike some hybrid inverters that reduce EPS output below their rated power, the KH8 delivers the full 8 kVA continuously in EPS mode with a 14,500 W, 60-second peak to handle motor and compressor start-up surges. No additional transfer switch hardware is required.
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FoxCloud V2.0 — Advanced Monitoring from Day One
The FoxCloud V2.0 platform provides real-time and historical system data: PV production, battery state of charge, grid power flow and household consumption — all accessible immediately via the included WiFi dongle and the Fox ESS app or browser portal. During EPS events, the platform records outage history. Optional 4G and LAN dongles ensure connectivity on challenging sites. The inverter also supports DRM (Demand Response Mode) for grid-operator compliance.
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Fanless Natural Cooling — Below 30 dB, No Moving Parts
The KH8 uses natural convection cooling with no fan — delivering sub-30 dB operating noise (quieter than a library reading room). Eliminating the fan removes the single most common mechanical failure point in inverters, improving long-term reliability and making the unit suitable for installation adjacent to living spaces. The IP65 housing means the inverter can be mounted outdoors, freeing up internal utility space.
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Parallel-Ready to 10 Units — Scale Without Limits
The KH8 supports parallel connection of up to ten units, enabling a combined single-phase output of up to 80 kW — suitable for large residential properties, farms, and light-commercial sites on single-phase supplies. Battery storage can be expanded independently: up to seven Fox battery modules in series per inverter string deliver a maximum of 33.24 kWh of storage per inverter without any additional controller hardware.
Technical Specifications — Fox ESS KH8 · Part No. FE-KH1-8.0
| PV Input |
| Max. Array Power |
16,000 Wp |
| Max. PV Input Power |
12,000 W |
| Max. DC Voltage |
600 V |
| Nominal DC Operating Voltage |
360 V |
| MPPT Voltage Range |
80 – 500 V |
| Start-up Voltage |
75 V |
| Number of MPPT Trackers |
3 |
| Strings per MPPT Tracker |
1 |
| Max. Input Current per Tracker |
16 A |
| Max. Short-Circuit Current per Tracker |
20 A |
| Max. Inverter Backfeed to Array |
0 mA |
| DC Disconnection Switch |
Optional |
| AC Output |
| Nominal AC Power |
8,000 VA |
| Max. Apparent AC Power |
8,800 VA |
| Rated Grid Voltage |
220 / 230 / 240 V (180–270 V range) |
| Rated Grid Frequency |
50 / 60 Hz (±5 Hz) |
| Nominal AC Current |
34.8 A |
| Max. AC Current |
38.3 A |
| Displacement Power Factor |
0.8 Lead – 0.8 Lag |
| THDi (at Rated Power) |
<3% |
| EPS Output (Emergency Power Supply — with Battery) |
| Max. EPS Continuous Power |
8,000 VA |
| EPS Peak Power (60 s) |
14,500 W |
| Max. EPS Current |
63.0 A |
| EPS Rated Voltage / Frequency |
220 / 230 / 240 V · 50 / 60 Hz |
| Grid-Loss Detection & Switch Time |
<6 ms |
| THDv (Linear Load) |
<2% |
| Parallel Operation |
Yes — up to 10 units |
| Battery |
| Battery Chemistry |
Li-Ion (high voltage) |
| Battery Voltage Range |
85 – 480 V |
| Recommended Battery Voltage |
300 V |
| Max. Charge Current |
50 A |
| Max. Discharge Current |
50 A |
| Battery Communication |
CAN / RS485 |
| Reverse Polarity Protection |
Yes |
| Max. Batteries in Series |
7 (up to 33.24 kWh) |
| Compatible Battery Range |
Fox ECS, HV2600, MIRA HV25, EP series |
| Efficiency |
| Max. Efficiency |
97.80% |
| European Efficiency |
97.40% |
| MPPT Efficiency |
99.90% |
| PV → Battery Charge Efficiency |
98.50% (full load) |
| Battery → AC Discharge Efficiency |
97.00% (full load) |
| Standby Consumption (idle) |
<2 W |
| Physical & Environmental |
| Dimensions (W × H × D) |
450 × 527 × 208 mm |
| Weight |
29 kg |
| Cooling Method |
Natural convection (fanless) |
| Topology |
Non-isolated, transformerless |
| Noise Emission (typical) |
<30 dB |
| Operating Temperature |
−25 to +60 °C (derating above +45 °C) |
| Storage Temperature |
−40 to +70 °C |
| Humidity |
0–95% RH (non-condensing) |
| Max. Installation Altitude |
<2,000 m |
| Ingress Protection |
IP65 |
| Protective Class |
Class I |
| Communications & Connectivity |
| WiFi |
Built-in (dongle included) |
| 4G / LAN |
Optional dongles |
| CT Clamp |
Included |
| Modbus Energy Meter |
Optional (recommended >30 m from grid supply) |
| Other Interfaces |
RS485, USB, DRM |
| Protection |
| PV Reverse Polarity |
Yes |
| Battery Reverse Polarity |
Yes |
| Anti-Islanding |
Active Frequency Drift with Positive Feedback |
| Output Short-Circuit |
Yes |
| Leakage Current Protection |
Yes |
| Insulation Resistance Detection |
Yes |
| Overcurrent / Overtemperature |
Yes |
| Overvoltage Category |
III (AC side) · II (DC side) |
| AC / DC Surge Protection |
Type II / Type II |
| AFCI Protection |
Optional |
| Certifications |
| Safety |
IEC 62109-1 / IEC 62109-2 / IEC 62477-1 |
| EMC |
EN 61000-6-1 / EN 61000-6-2 / EN 61000-6-3 |
| Grid Connection (UK) |
G99 / EN50549 / NRS 097-2-1 |
| Country of Manufacture |
China |
Frequently Asked Questions
What is the difference between the KH8 and the KH7?
The KH8 delivers 8 kW of continuous AC output versus 7 kW on the KH7, and can accept a larger solar array — up to 16,000 Wp (vs 15,000 Wp) with a higher maximum PV input power of 12,000 W (vs 10,500 W). The EPS peak power is slightly higher at 14,500 W vs 14,000 W. Both models share the same physical housing, three MPPT trackers, battery interface, efficiency figures, IP65 rating, fanless cooling, and G99 certification. The KH8 is the better choice where the roof can support a larger array, or where household load regularly approaches or exceeds 7 kW.
Which Fox ESS batteries are compatible with the KH8?
The KH8 is compatible with the full Fox ESS high-voltage lithium-ion battery range: the ECS series (ECS2900, ECS4100, ECS4300, ECS4800), the HV2600, the MIRA HV25, and the EP series. Up to seven modules can be connected in series, providing a maximum storage capacity of 33.24 kWh. Third-party battery brands are not supported, and their use would void the inverter warranty.
Does the KH8 provide full backup power during a power cut?
Yes. The integrated EPS (Emergency Power Supply) function detects grid loss and switches to battery supply in under 6 milliseconds — fast enough to prevent most sensitive electronics from restarting. In EPS mode the KH8 provides the full 8 kVA continuously (no derating), with a 14,500 W surge for up to 60 seconds to handle motor and compressor start-up currents. The inverter resumes normal grid-tied operation automatically once supply is restored.
Does the KH8 qualify for Smart Export Guarantee (SEG) payments?
Yes, provided the system is installed by an MCS-certified installer and registered on the MCS database. The KH8 is G99-certified for UK grid connection and MCS-compatible. Once registration is complete, the homeowner can apply to an SEG-licensed energy supplier to receive export payments for surplus electricity sent to the grid. Rates and eligibility criteria vary by supplier.
Can I add the KH8 to an existing solar system that already has an inverter?
No — the KH8 is a DC-coupled hybrid inverter and must connect directly to the solar PV strings. It replaces any existing string inverter rather than working alongside it. If the goal is to add battery storage to a working solar system without changing the current inverter, the Fox ESS KA8 (AC Coupled version) connects on the AC bus and is the appropriate product for that scenario.
What monitoring is included, and is a separate data logger needed?
No separate data logger is required. The KH8 ships with a WiFi dongle giving immediate access to the FoxCloud V2.0 platform — accessible via the Fox ESS smartphone app or web portal. Live and historical data covers PV production, battery state of charge, grid import/export and household consumption. A CT clamp is included in the box for grid monitoring. Optional 4G and LAN dongles are available for sites without reliable WiFi. A Modbus energy meter (sold separately) is recommended when the cable run from inverter to grid supply exceeds 30 metres.
Specifications sourced from Fox ESS K-Series Datasheet v2.3 (September 2025). Always verify against current manufacturer documentation before specifying. Installation must be carried out by a suitably qualified engineer in accordance with G99, BS 7671, and applicable MCS standards.
