Fox ESS announced the launch of the H3 Smart on 18 July 2025, describing it as a brand-new three-phase hybrid inverter range with models from 5 kW to 15 kW1. The company said the range is available now from authorised Fox ESS distribution partners across the UK1.
The H3 Smart is aimed at properties with higher energy demands, which Fox ESS lists as large homes, multi-family dwellings and commercial sites1. The company states that ideal applications include small commercial installations, agricultural or rural properties, high-consumption domestic homes, EV-ready sites, and smart energy retrofits and new builds1. It supports up to three MPPTs, which Fox ESS says allows flexible PV configurations across multiple roof orientations, and it is fully compatible with the company's full range of LFP HV battery options1.
Fox ESS lists the following features for the range1:
| Feature | Detail as stated by Fox ESS |
|---|---|
| Power range | 5 kW to 15 kW |
| Phases | Three-phase |
| Backup | Built-in EPS output, no external ATS required |
| Connectivity | Built-in Wi-Fi, no plugin dongle needed |
| Installation | Plug-and-play design |
| Firmware | Upgraded architecture for smoother updates |
| MPPTs | Up to three |
| Grid compliance | Full G99 compliance |
| Battery compatibility | Full range of LFP HV battery options |
"With full G99 compliance, class-leading efficiency, and integrated EPS functionality, the H3 Smart is ready for the UK market."
The announcement gives no prices for any model in the range, and no efficiency figures beyond the phrase "class-leading efficiency"1. No warranty terms, dimensions, weight or per-model specifications have been reported1. Fox ESS directs readers to fox-ess.tech for datasheets and installation guides, or to its UK service team for product enquiries1.
Why it matters for households
A hybrid inverter sits at the centre of a home energy system, managing solar generation, battery charging and discharge, and the flow of power to and from the grid. For homes on a three-phase supply, which include some larger properties and converted or multi-occupancy buildings, the choice of hybrid inverter has until now been narrower than for single-phase homes. The H3 Smart extends that choice up to 15 kW1.
The built-in EPS output is the feature with the most direct bearing on energy independence. EPS, or emergency power supply, allows the inverter to keep selected circuits running from the battery during a grid outage. Fox ESS states that the H3 Smart provides this without an external ATS, the automatic transfer switch that would otherwise be needed to isolate the property from the grid1. That removes a separate box from the installation and one more component that could fail.
Built-in Wi-Fi means monitoring and firmware updates do not depend on a plug-in dongle1, and the upgraded firmware architecture is described as supporting smoother updates and advanced energy features1. For a household, that affects how easily a system can be monitored and how it might gain new functions over time.
G99 compliance matters because it is the engineering standard that governs how a generating unit connects to the UK distribution network1. A compliant inverter is a precondition for a grid connection application, though the connection itself still depends on the local network operator.
How the H3 Smart compares on price, warranty or measured efficiency against other three-phase hybrid inverters has not been reported1.
What happens next
Fox ESS states the H3 Smart is available now from authorised UK distribution partners1. Datasheets and installation guides are directed to fox-ess.tech1. No dates have been given for further model announcements, firmware releases or specification publications1.
Sources1 cited
- H3 Smart 3-Phase Hybrid Inverter | Fox ESS UK, fox-ess.uk