Fox ESS EP5 Battery 5.18kWh

Fox ESS has become one of the most-installed hybrid inverter brands in the UK in the last two years, and the EP5 is their current 5.18kWh high-voltage stackable LiFePO4 battery module. Pair with a Fox ESS H1, KH, H3 or H3-Pro hybrid inverter for an integrated system.

The EP5 uses LFP (LiFePO4) cells with an integrated battery management system and a full 100% usable depth of discharge — its 5.18kWh nominal energy is also its 5.18kWh usable capacity. Stack up to 4 modules in parallel per Fox inverter for 20.8kWh total capacity. The standard warranty is 5 years, extendable to 10 years for an additional fee.

Who it suits

Installs already running or planning a Fox ESS hybrid inverter — the integration is mature, well-supported by UK installers, and the Fox cloud monitoring is solid. Also a strong cost-per-kWh option in the mid tier, with an IP65 rating that allows indoor or outdoor mounting.

What I'd watch for

Best paired with Fox ESS inverters — third-party compatibility is limited. Fox ESS warranty support quality varies by installer — choose an installer with established Fox accreditation, and budget for the warranty extension if you want full 10-year cover.