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Fox ESS EPS-BOX-SP Single Phase Whole Home Backup Gateway
The Fox ESS EPS-BOX-SP (FE-EPS-BOX-SP) is a single-phase whole-home backup gateway that enables an existing Fox ESS hybrid inverter and battery system to power the entire property — not just a handful of emergency sockets — during a grid outage. It sits between the utility supply, the Fox ESS inverter, and the household consumer unit. During normal operation it is transparent to the system. When the grid fails, it automatically isolates the property and restores power via battery and solar within 2–3 seconds. When the grid recovers, it reconnects seamlessly. The unit handles up to 100A output current, covers the full range of UK single-phase Fox ESS hybrid inverters and AC chargers, and comes in an IP65-rated metal enclosure suitable for both indoor and sheltered outdoor installation.
100 A
Max output current
2–3 sec
Typical transfer time
Whole home
All circuits backed up
IP65
Metal enclosure
Automatic
No user intervention
⚠ Installer Note — Installation must be carried out by a qualified electrician registered with a competent persons scheme (NICEIC, NAPIT). The EPS-BOX-SP modifies the interaction between the property and the grid at the main supply point; work must comply with BS 7671 and any applicable DNO requirements. This is a system accessory — a compatible Fox ESS hybrid inverter and battery must already be installed or supplied alongside. The box does not generate or store energy itself.
⚡ Compatibility — Single Phase Only
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Features & Benefits
✔ Whole-Home Backup — Every Circuit
Traditional EPS outputs from a hybrid inverter power only the inverter's own backup socket or a dedicated sub-board. The EPS-BOX-SP connects between the inverter and the main consumer unit, enabling the battery and solar system to power all circuits in the property — heating, lighting, kitchen, EV charger (subject to inverter output and battery capacity) — during an outage. No rewiring of individual circuits is required.
✔ Automatic Switchover — No User Action
When the grid supply fails, the EPS-BOX-SP automatically detects the loss of voltage, disconnects from the utility supply, and restores power from the Fox ESS inverter's EPS output — typically within 2–3 seconds. When grid power returns and is stable, the unit reconnects automatically. The homeowner does not need to flip switches, press buttons, or do anything.
✔ 100A Output — Handles Full UK Domestic Load
With a maximum output current of 100A at 220/230/240V single-phase, the EPS-BOX-SP can accommodate the main supply capacity of the vast majority of UK domestic properties — most of which are fused at 60A, 80A, or 100A at the service head. This means the backup gateway does not become a bottleneck that limits which circuits can be powered during an outage.
✔ Grid-Compliant Isolation
The EPS-BOX-SP provides automatic electrical isolation from the grid during backup operation — a requirement for any system operating in island mode in the UK. This protects DNO engineers working on the network from back-fed voltage from your battery system, and ensures the inverter is not damaged by a voltage conflict when the grid returns. It fulfils the islanding protection requirement of the Fox ESS system in a single box.
✔ Integrated RS-485 Meter Communication
The unit includes an RS-485 communication interface and is designed to integrate with the Fox ESS system's metering and monitoring. This enables the FoxESS Cloud platform and app to report backup status, track energy flows during outage periods, and allow the installer to configure switching behaviour via the inverter settings.
✔ IP65 Metal Enclosure — Indoor or Outdoor
The IP65-rated metal housing protects against dust ingress and water jet spray, making the unit suitable for installation in garages, utility rooms, outbuildings, and sheltered outdoor wall locations. Operating temperature range of –25°C to +60°C ensures reliable performance through UK winter conditions without heating or climate control.
✔ Retrofit Compatible
The EPS-BOX-SP can be added to an existing Fox ESS single-phase hybrid inverter installation — it does not require a new inverter or battery to be installed. For homes with a Fox ESS H1-G2, KH, EVO, or PowerQ inverter and battery already fitted, the EPS-BOX-SP upgrades the system to whole-home backup without any other changes to the solar or storage hardware.
✔ Silent, Maintenance-Free Cooling
The EPS-BOX-SP uses natural convection cooling — no fans, no moving parts, no noise. This makes it suitable for installation near living spaces and means there is no maintenance obligation beyond the periodic inspection appropriate for any electrical installation. No filters to clean, no components that wear out through normal operation.
How It Works
The EPS-BOX-SP connects between three points: the utility supply (grid), the Fox ESS inverter's EPS output, and the property's consumer unit (household loads).
- Normal operation: The grid supplies the property as normal. Solar and battery charge/discharge via the Fox ESS inverter as usual. The EPS-BOX-SP is transparent — it does not affect normal system operation.
- Grid outage: The EPS-BOX-SP detects loss of grid voltage. It disconnects the property from the utility supply (isolating from the grid) and, after a short transfer delay of approximately 2–3 seconds, connects the consumer unit to the Fox ESS inverter's EPS output. The home is now powered by battery and solar.
- Grid restoration: When the grid returns and is stable, the EPS-BOX-SP automatically reconnects to the utility supply and returns to normal operation. No user action required.
Technical Specifications
| Manufacturer | Fox ESS |
| Part Number / SKU | FE-EPS-BOX-SP / EPS-BOX-SP |
| Product Type | Single-phase whole-home EPS backup gateway |
| Rated Voltage | 220 / 230 / 240 V AC, L / N / PE |
| Rated Frequency | 50 / 60 Hz |
| Max Output Current | 100 A |
| Typical Transfer Time (Grid Failure) | Approximately 2–3 seconds |
| Communication Interface | RS-485 (for meter / Fox ESS system integration) |
| Cooling | Natural convection (fanless — silent) |
| Mounting | Wall-mounted |
| Operating Temperature | –25°C to +60°C |
| Dimensions (W × H × D) | 420 × 550 × 138.5 mm |
| Net Weight | 16 kg |
| Ingress Protection | IP65 (dust-tight, jet-water resistant) |
| Compatible Inverters | Fox ESS H1-G2, KH Series, EVO, PowerQ (single-phase only) |
| Compatible AC Chargers | Fox ESS AC charger range (single-phase) |
Frequently Asked Questions
What is the difference between using the inverter's built-in EPS and adding an EPS-BOX-SP?
Fox ESS hybrid inverters have a built-in EPS (Emergency Power Supply) output — a dedicated socket or output terminal that provides backup power during an outage. However, this EPS output is separate from the main consumer unit — it only powers loads that are connected directly to it, typically a few sockets or a small sub-board. The EPS-BOX-SP connects the inverter's EPS output to the whole property's consumer unit, so that every circuit in the home is backed up — not just a dedicated emergency circuit. Think of it as the missing link between an EPS-capable inverter and a whole-home backup capability.
Will every appliance in the house keep working during a power cut?
The EPS-BOX-SP enables backup power to reach every circuit, but what actually keeps running depends on two things: the inverter's EPS output power rating (how many watts it can supply in backup mode) and the battery's state of charge and capacity (how long it can sustain that output). For example, a Fox ESS H1-6.0kW inverter can deliver up to 6kW in EPS mode — enough to run lights, heating pump, fridge, TV, and many other appliances simultaneously. High-draw appliances like electric showers (8–10 kW) or electric ovens may exceed the inverter's EPS output and could trip the backup. Your installer can advise on load management based on your specific inverter and battery combination.
Is there a risk of back-feeding the grid during backup operation?
No — this is exactly what the EPS-BOX-SP prevents. During backup operation, it physically disconnects the property from the utility supply, meaning the inverter and battery cannot back-feed voltage onto the grid cable. This is a critical safety requirement: DNO engineers responding to a power cut must not encounter live voltage on cables they believe to be de-energised. The EPS-BOX-SP provides this isolation automatically as soon as a grid failure is detected, and maintains it until the grid is confirmed stable.
Can this be retrofitted to an existing Fox ESS installation?
Yes — the EPS-BOX-SP is designed for both new installations and retrofit onto existing Fox ESS single-phase hybrid inverter systems. No changes to the inverter, batteries, or solar array are required. The installer will connect the EPS-BOX-SP between the existing inverter's EPS output and the household consumer unit. Confirm with your installer that the inverter firmware is up to date, as newer firmware versions may include improved EPS-BOX-SP integration features. Not all Fox ESS inverter models support the EPS-BOX-SP; check the compatibility list before ordering.
$256.50
Original: $732.87
-65%Fox ESS EPS-BOX-SP Single Phase Whole Home Backup Gateway—
$732.87
$256.50More Images
Fox ESS EPS-BOX-SP Single Phase Whole Home Backup Gateway
The Fox ESS EPS-BOX-SP (FE-EPS-BOX-SP) is a single-phase whole-home backup gateway that enables an existing Fox ESS hybrid inverter and battery system to power the entire property — not just a handful of emergency sockets — during a grid outage. It sits between the utility supply, the Fox ESS inverter, and the household consumer unit. During normal operation it is transparent to the system. When the grid fails, it automatically isolates the property and restores power via battery and solar within 2–3 seconds. When the grid recovers, it reconnects seamlessly. The unit handles up to 100A output current, covers the full range of UK single-phase Fox ESS hybrid inverters and AC chargers, and comes in an IP65-rated metal enclosure suitable for both indoor and sheltered outdoor installation.
100 A
Max output current
2–3 sec
Typical transfer time
Whole home
All circuits backed up
IP65
Metal enclosure
Automatic
No user intervention
⚠ Installer Note — Installation must be carried out by a qualified electrician registered with a competent persons scheme (NICEIC, NAPIT). The EPS-BOX-SP modifies the interaction between the property and the grid at the main supply point; work must comply with BS 7671 and any applicable DNO requirements. This is a system accessory — a compatible Fox ESS hybrid inverter and battery must already be installed or supplied alongside. The box does not generate or store energy itself.
⚡ Compatibility — Single Phase Only
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Features & Benefits
✔ Whole-Home Backup — Every Circuit
Traditional EPS outputs from a hybrid inverter power only the inverter's own backup socket or a dedicated sub-board. The EPS-BOX-SP connects between the inverter and the main consumer unit, enabling the battery and solar system to power all circuits in the property — heating, lighting, kitchen, EV charger (subject to inverter output and battery capacity) — during an outage. No rewiring of individual circuits is required.
✔ Automatic Switchover — No User Action
When the grid supply fails, the EPS-BOX-SP automatically detects the loss of voltage, disconnects from the utility supply, and restores power from the Fox ESS inverter's EPS output — typically within 2–3 seconds. When grid power returns and is stable, the unit reconnects automatically. The homeowner does not need to flip switches, press buttons, or do anything.
✔ 100A Output — Handles Full UK Domestic Load
With a maximum output current of 100A at 220/230/240V single-phase, the EPS-BOX-SP can accommodate the main supply capacity of the vast majority of UK domestic properties — most of which are fused at 60A, 80A, or 100A at the service head. This means the backup gateway does not become a bottleneck that limits which circuits can be powered during an outage.
✔ Grid-Compliant Isolation
The EPS-BOX-SP provides automatic electrical isolation from the grid during backup operation — a requirement for any system operating in island mode in the UK. This protects DNO engineers working on the network from back-fed voltage from your battery system, and ensures the inverter is not damaged by a voltage conflict when the grid returns. It fulfils the islanding protection requirement of the Fox ESS system in a single box.
✔ Integrated RS-485 Meter Communication
The unit includes an RS-485 communication interface and is designed to integrate with the Fox ESS system's metering and monitoring. This enables the FoxESS Cloud platform and app to report backup status, track energy flows during outage periods, and allow the installer to configure switching behaviour via the inverter settings.
✔ IP65 Metal Enclosure — Indoor or Outdoor
The IP65-rated metal housing protects against dust ingress and water jet spray, making the unit suitable for installation in garages, utility rooms, outbuildings, and sheltered outdoor wall locations. Operating temperature range of –25°C to +60°C ensures reliable performance through UK winter conditions without heating or climate control.
✔ Retrofit Compatible
The EPS-BOX-SP can be added to an existing Fox ESS single-phase hybrid inverter installation — it does not require a new inverter or battery to be installed. For homes with a Fox ESS H1-G2, KH, EVO, or PowerQ inverter and battery already fitted, the EPS-BOX-SP upgrades the system to whole-home backup without any other changes to the solar or storage hardware.
✔ Silent, Maintenance-Free Cooling
The EPS-BOX-SP uses natural convection cooling — no fans, no moving parts, no noise. This makes it suitable for installation near living spaces and means there is no maintenance obligation beyond the periodic inspection appropriate for any electrical installation. No filters to clean, no components that wear out through normal operation.
How It Works
The EPS-BOX-SP connects between three points: the utility supply (grid), the Fox ESS inverter's EPS output, and the property's consumer unit (household loads).
- Normal operation: The grid supplies the property as normal. Solar and battery charge/discharge via the Fox ESS inverter as usual. The EPS-BOX-SP is transparent — it does not affect normal system operation.
- Grid outage: The EPS-BOX-SP detects loss of grid voltage. It disconnects the property from the utility supply (isolating from the grid) and, after a short transfer delay of approximately 2–3 seconds, connects the consumer unit to the Fox ESS inverter's EPS output. The home is now powered by battery and solar.
- Grid restoration: When the grid returns and is stable, the EPS-BOX-SP automatically reconnects to the utility supply and returns to normal operation. No user action required.
Technical Specifications
| Manufacturer | Fox ESS |
| Part Number / SKU | FE-EPS-BOX-SP / EPS-BOX-SP |
| Product Type | Single-phase whole-home EPS backup gateway |
| Rated Voltage | 220 / 230 / 240 V AC, L / N / PE |
| Rated Frequency | 50 / 60 Hz |
| Max Output Current | 100 A |
| Typical Transfer Time (Grid Failure) | Approximately 2–3 seconds |
| Communication Interface | RS-485 (for meter / Fox ESS system integration) |
| Cooling | Natural convection (fanless — silent) |
| Mounting | Wall-mounted |
| Operating Temperature | –25°C to +60°C |
| Dimensions (W × H × D) | 420 × 550 × 138.5 mm |
| Net Weight | 16 kg |
| Ingress Protection | IP65 (dust-tight, jet-water resistant) |
| Compatible Inverters | Fox ESS H1-G2, KH Series, EVO, PowerQ (single-phase only) |
| Compatible AC Chargers | Fox ESS AC charger range (single-phase) |
Frequently Asked Questions
What is the difference between using the inverter's built-in EPS and adding an EPS-BOX-SP?
Fox ESS hybrid inverters have a built-in EPS (Emergency Power Supply) output — a dedicated socket or output terminal that provides backup power during an outage. However, this EPS output is separate from the main consumer unit — it only powers loads that are connected directly to it, typically a few sockets or a small sub-board. The EPS-BOX-SP connects the inverter's EPS output to the whole property's consumer unit, so that every circuit in the home is backed up — not just a dedicated emergency circuit. Think of it as the missing link between an EPS-capable inverter and a whole-home backup capability.
Will every appliance in the house keep working during a power cut?
The EPS-BOX-SP enables backup power to reach every circuit, but what actually keeps running depends on two things: the inverter's EPS output power rating (how many watts it can supply in backup mode) and the battery's state of charge and capacity (how long it can sustain that output). For example, a Fox ESS H1-6.0kW inverter can deliver up to 6kW in EPS mode — enough to run lights, heating pump, fridge, TV, and many other appliances simultaneously. High-draw appliances like electric showers (8–10 kW) or electric ovens may exceed the inverter's EPS output and could trip the backup. Your installer can advise on load management based on your specific inverter and battery combination.
Is there a risk of back-feeding the grid during backup operation?
No — this is exactly what the EPS-BOX-SP prevents. During backup operation, it physically disconnects the property from the utility supply, meaning the inverter and battery cannot back-feed voltage onto the grid cable. This is a critical safety requirement: DNO engineers responding to a power cut must not encounter live voltage on cables they believe to be de-energised. The EPS-BOX-SP provides this isolation automatically as soon as a grid failure is detected, and maintains it until the grid is confirmed stable.
Can this be retrofitted to an existing Fox ESS installation?
Yes — the EPS-BOX-SP is designed for both new installations and retrofit onto existing Fox ESS single-phase hybrid inverter systems. No changes to the inverter, batteries, or solar array are required. The installer will connect the EPS-BOX-SP between the existing inverter's EPS output and the household consumer unit. Confirm with your installer that the inverter firmware is up to date, as newer firmware versions may include improved EPS-BOX-SP integration features. Not all Fox ESS inverter models support the EPS-BOX-SP; check the compatibility list before ordering.
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
The Fox ESS EPS-BOX-SP (FE-EPS-BOX-SP) is a single-phase whole-home backup gateway that enables an existing Fox ESS hybrid inverter and battery system to power the entire property — not just a handful of emergency sockets — during a grid outage. It sits between the utility supply, the Fox ESS inverter, and the household consumer unit. During normal operation it is transparent to the system. When the grid fails, it automatically isolates the property and restores power via battery and solar within 2–3 seconds. When the grid recovers, it reconnects seamlessly. The unit handles up to 100A output current, covers the full range of UK single-phase Fox ESS hybrid inverters and AC chargers, and comes in an IP65-rated metal enclosure suitable for both indoor and sheltered outdoor installation.
100 A
Max output current
2–3 sec
Typical transfer time
Whole home
All circuits backed up
IP65
Metal enclosure
Automatic
No user intervention
⚠ Installer Note — Installation must be carried out by a qualified electrician registered with a competent persons scheme (NICEIC, NAPIT). The EPS-BOX-SP modifies the interaction between the property and the grid at the main supply point; work must comply with BS 7671 and any applicable DNO requirements. This is a system accessory — a compatible Fox ESS hybrid inverter and battery must already be installed or supplied alongside. The box does not generate or store energy itself.
⚡ Compatibility — Single Phase Only
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Compatible with: Fox ESS H1-G2, KH Series, EVO, PowerQ single-phase hybrid inverters, and Fox ESS AC chargers.
Not compatible with: Three-phase Fox ESS inverter systems (see the Fox ESS EPS-BOX-PRO / EPS-BOX-TP for three-phase applications). Backup performance is subject to inverter and battery sizing — sufficient battery capacity and inverter power rating must be available to meet the property's load during an outage.
Features & Benefits
✔ Whole-Home Backup — Every Circuit
Traditional EPS outputs from a hybrid inverter power only the inverter's own backup socket or a dedicated sub-board. The EPS-BOX-SP connects between the inverter and the main consumer unit, enabling the battery and solar system to power all circuits in the property — heating, lighting, kitchen, EV charger (subject to inverter output and battery capacity) — during an outage. No rewiring of individual circuits is required.
✔ Automatic Switchover — No User Action
When the grid supply fails, the EPS-BOX-SP automatically detects the loss of voltage, disconnects from the utility supply, and restores power from the Fox ESS inverter's EPS output — typically within 2–3 seconds. When grid power returns and is stable, the unit reconnects automatically. The homeowner does not need to flip switches, press buttons, or do anything.
✔ 100A Output — Handles Full UK Domestic Load
With a maximum output current of 100A at 220/230/240V single-phase, the EPS-BOX-SP can accommodate the main supply capacity of the vast majority of UK domestic properties — most of which are fused at 60A, 80A, or 100A at the service head. This means the backup gateway does not become a bottleneck that limits which circuits can be powered during an outage.
✔ Grid-Compliant Isolation
The EPS-BOX-SP provides automatic electrical isolation from the grid during backup operation — a requirement for any system operating in island mode in the UK. This protects DNO engineers working on the network from back-fed voltage from your battery system, and ensures the inverter is not damaged by a voltage conflict when the grid returns. It fulfils the islanding protection requirement of the Fox ESS system in a single box.
✔ Integrated RS-485 Meter Communication
The unit includes an RS-485 communication interface and is designed to integrate with the Fox ESS system's metering and monitoring. This enables the FoxESS Cloud platform and app to report backup status, track energy flows during outage periods, and allow the installer to configure switching behaviour via the inverter settings.
✔ IP65 Metal Enclosure — Indoor or Outdoor
The IP65-rated metal housing protects against dust ingress and water jet spray, making the unit suitable for installation in garages, utility rooms, outbuildings, and sheltered outdoor wall locations. Operating temperature range of –25°C to +60°C ensures reliable performance through UK winter conditions without heating or climate control.
✔ Retrofit Compatible
The EPS-BOX-SP can be added to an existing Fox ESS single-phase hybrid inverter installation — it does not require a new inverter or battery to be installed. For homes with a Fox ESS H1-G2, KH, EVO, or PowerQ inverter and battery already fitted, the EPS-BOX-SP upgrades the system to whole-home backup without any other changes to the solar or storage hardware.
✔ Silent, Maintenance-Free Cooling
The EPS-BOX-SP uses natural convection cooling — no fans, no moving parts, no noise. This makes it suitable for installation near living spaces and means there is no maintenance obligation beyond the periodic inspection appropriate for any electrical installation. No filters to clean, no components that wear out through normal operation.
How It Works
The EPS-BOX-SP connects between three points: the utility supply (grid), the Fox ESS inverter's EPS output, and the property's consumer unit (household loads).
- Normal operation: The grid supplies the property as normal. Solar and battery charge/discharge via the Fox ESS inverter as usual. The EPS-BOX-SP is transparent — it does not affect normal system operation.
- Grid outage: The EPS-BOX-SP detects loss of grid voltage. It disconnects the property from the utility supply (isolating from the grid) and, after a short transfer delay of approximately 2–3 seconds, connects the consumer unit to the Fox ESS inverter's EPS output. The home is now powered by battery and solar.
- Grid restoration: When the grid returns and is stable, the EPS-BOX-SP automatically reconnects to the utility supply and returns to normal operation. No user action required.
Technical Specifications
| Manufacturer | Fox ESS |
| Part Number / SKU | FE-EPS-BOX-SP / EPS-BOX-SP |
| Product Type | Single-phase whole-home EPS backup gateway |
| Rated Voltage | 220 / 230 / 240 V AC, L / N / PE |
| Rated Frequency | 50 / 60 Hz |
| Max Output Current | 100 A |
| Typical Transfer Time (Grid Failure) | Approximately 2–3 seconds |
| Communication Interface | RS-485 (for meter / Fox ESS system integration) |
| Cooling | Natural convection (fanless — silent) |
| Mounting | Wall-mounted |
| Operating Temperature | –25°C to +60°C |
| Dimensions (W × H × D) | 420 × 550 × 138.5 mm |
| Net Weight | 16 kg |
| Ingress Protection | IP65 (dust-tight, jet-water resistant) |
| Compatible Inverters | Fox ESS H1-G2, KH Series, EVO, PowerQ (single-phase only) |
| Compatible AC Chargers | Fox ESS AC charger range (single-phase) |
Frequently Asked Questions
What is the difference between using the inverter's built-in EPS and adding an EPS-BOX-SP?
Fox ESS hybrid inverters have a built-in EPS (Emergency Power Supply) output — a dedicated socket or output terminal that provides backup power during an outage. However, this EPS output is separate from the main consumer unit — it only powers loads that are connected directly to it, typically a few sockets or a small sub-board. The EPS-BOX-SP connects the inverter's EPS output to the whole property's consumer unit, so that every circuit in the home is backed up — not just a dedicated emergency circuit. Think of it as the missing link between an EPS-capable inverter and a whole-home backup capability.
Will every appliance in the house keep working during a power cut?
The EPS-BOX-SP enables backup power to reach every circuit, but what actually keeps running depends on two things: the inverter's EPS output power rating (how many watts it can supply in backup mode) and the battery's state of charge and capacity (how long it can sustain that output). For example, a Fox ESS H1-6.0kW inverter can deliver up to 6kW in EPS mode — enough to run lights, heating pump, fridge, TV, and many other appliances simultaneously. High-draw appliances like electric showers (8–10 kW) or electric ovens may exceed the inverter's EPS output and could trip the backup. Your installer can advise on load management based on your specific inverter and battery combination.
Is there a risk of back-feeding the grid during backup operation?
No — this is exactly what the EPS-BOX-SP prevents. During backup operation, it physically disconnects the property from the utility supply, meaning the inverter and battery cannot back-feed voltage onto the grid cable. This is a critical safety requirement: DNO engineers responding to a power cut must not encounter live voltage on cables they believe to be de-energised. The EPS-BOX-SP provides this isolation automatically as soon as a grid failure is detected, and maintains it until the grid is confirmed stable.
Can this be retrofitted to an existing Fox ESS installation?
Yes — the EPS-BOX-SP is designed for both new installations and retrofit onto existing Fox ESS single-phase hybrid inverter systems. No changes to the inverter, batteries, or solar array are required. The installer will connect the EPS-BOX-SP between the existing inverter's EPS output and the household consumer unit. Confirm with your installer that the inverter firmware is up to date, as newer firmware versions may include improved EPS-BOX-SP integration features. Not all Fox ESS inverter models support the EPS-BOX-SP; check the compatibility list before ordering.
