Fox ESS EP6 and EP12 batteries: capacities and specifications

The Fox ESS EP battery range is sold in two headline models: the EP6 at 5.76kWh and the EP12 at 11.52kWh¹. Both are high-voltage units designed to sit on a wall, and both are scalable, with up to four units connected in parallel¹. For a household, the choice between them is mostly about how much storage the house needs and how much wall space is available, since the two models share the same system architecture and the same inverter compatibility.

The EP12 is the larger of the two, and it is the one most often quoted in UK system designs. A single unit gives 11.52kWh of nominal capacity, and four units give 46.08kWh². Fox ESS lists a largest system of eight EP12 units at 92.16kWh on its H3 Pro inverter page, which reflects the wider system rather than a single stack³. The EP6 is the smaller unit, at 5.76kWh each, modular up to 23.04kWh across four units².

What follows sets out the capacities, the wider EP family, the specifications, the inverters that pair with the range, the junction box rule for stacked installations, UK pricing, and what the choice means for a household's energy independence.

EP6 and EP12 at a glance: capacities and what each model is

The EP6 and EP12 are the two models Fox ESS names in its EP battery range, at 5.76kWh and 11.52kWh respectively¹. Both are described by the maker as high-performance, scalable battery storage systems suitable for a broad range of storage applications⁵. The EP6 is listed as modular up to 23.04kWh in total across four units, and the EP12 as 11.52 to 46.08kWh across one to four batteries².

The practical difference is granularity. A household that needs around 11.52kWh of storage can reach it with one EP12 or with two EP6 units, and the two routes give the same nominal capacity but a different number of boxes on the wall and a different number of connections. The EP6 route also allows capacity to be added in smaller steps later, since each additional unit adds 5.76kWh rather than 11.52kWh.

Both models are slimline for wall mounting, which matters in a garage or utility room where floor space is at a premium¹. Fox ESS describes its high-voltage residential battery systems as designed to operate with compatible hybrid inverters as part of an integrated residential energy system, so the battery is not a standalone product: it is one part of a system that includes an inverter and, usually, solar⁷.

The wider EP range: EP5, EP6 Plus and EP12 Plus

The EP6 and EP12 are not the whole family. Fox ESS lists the EP series as EP5, EP6, EP11 and EP12³. The EP5 is described as a high voltage storage battery⁶. The EP11 sits between the EP6 and EP12 in capacity terms, with a nominal capacity of 10.36kW⁷.

The Plus variants are the newer additions. The EP6 Plus datasheet lists an LED display, CAN communication and a maximum of four units in parallel⁸. The EP12 Plus datasheet lists LFP (LiFePO4) chemistry, an LED display and scalability of a maximum of four units in parallel⁹. The EP12 Plus is also listed as an expandable system with safety and reliability as its stated characteristics⁶.

The naming is worth reading carefully. A household comparing an EP12 with an EP12 Plus is comparing two different products in the same family, not two versions of one product. The Plus models carry their own datasheets and their own specifications, and the parallel limit of four units applies to the Plus models as well as to the headline units⁹.

Fox ESS also sells the EQ and CQ battery ranges alongside the EP range, and the EQ range is described as a modular, high-voltage battery range for residential energy storage systems with natural convection cooling and CAN communication¹¹. The EQ range is covered separately on Fox ESS EQ series batteries.

Specifications: high-voltage batteries with heating element options

The EP range is a high-voltage family. Fox ESS describes its residential battery systems as high-voltage, and the EP batteries pair with hybrid inverters rather than with the low-voltage inverters used by some other makers⁷. No nominal voltage figure for the EP6 or EP12 is published in the sources cited here.

On heating, the position is more specific for the EQ range than for the EP range. Fox ESS publishes a battery warm-up function for the EQ battery range and states that availability varies by model and system configuration, that it is not available on the EQ4800, and that it is available on the EQ2900, EQ4300 and EQ5000 only when the system includes both EQ master and slave units, with warming disabled when EQ slave batteries are paired with legacy ECS versions¹¹. That is a conditional feature, not a standard one, and it is described for the EQ range rather than the EP range.

The EP12 Plus datasheet gives LFP (LiFePO4) chemistry, which is the lithium iron phosphate chemistry common in home storage⁹. LFP is one of several chemistries sold for home batteries, and the differences between them are set out on Home Battery Chemistries: LFP, NMC and What Else Is Sold.

Which Fox ESS inverters and systems pair with the EP range

Fox ESS states that its KH and KA series single-phase hybrid inverters pair with Fox ESS high-voltage batteries including the EP, EQ and CQ battery ranges¹. That is the clearest compatibility statement for the EP range, and it names the EP range directly.

Beyond that, several Fox ESS hybrid inverters are described as compatible with the company's own range of high-voltage batteries. The P100, the PowerQ, the Power Cube and the S28 are each listed that way¹². The wording is the maker's own and refers to the high-voltage range as a whole rather than to the EP6 or EP12 by name, so a household should confirm the specific pairing before ordering.

The H1 G2 and AC1 G2 hybrid inverters provide EPS output with a battery, with peak output apparent power of 3600, 4400, 5500, 6000 and 7200VA for 60 seconds across the model range in ascending rated power order¹⁶. The WL variants of the same inverters carry the same peak output figures by model¹⁷. The H1-6.0-E-G2 and AC1-6.0-E-G2 take a maximum array power of 12000Wp¹⁶. The H3 and AC3 are three-phase hybrid and AC inverters¹⁸.

The EPS Box SP is a separate product for backup. Fox ESS states it is fully compatible with the existing single-phase hybrid inverter range, and lists compatibility with H1-G2, KH, EVO and PowerQ inverters¹⁹. It provides whole home backup for residential storage installations, isolating the property from the grid and, after a short transfer delay, restoring power using battery and solar during a grid outage²⁰. Backup arrangements are covered in more detail on Battery Backup in a Power Cut: EPS, Changeover and What Keeps Running.

Stacking and installation: the junction box requirement for 2 to 4 batteries

Fox ESS states that for installations of two to four EP batteries a junction box is required¹. A single battery does not need one. That is the single most important installation rule for anyone planning a stack, because it changes the parts list and the labour for any system with more than one EP unit.

The parallel limit is four units¹. The EP12 Plus datasheet gives the same limit of a maximum of four units in parallel⁹, and the EP6 Plus datasheet likewise⁸. So the ceiling is consistent across the range: four batteries per stack, with a junction box once there are two or more.

Fox ESS states that battery models are not mixed within a system³. An installation therefore uses one model throughout, so a household that starts with an EP6 and later wants more capacity adds another EP6 rather than an EP12. That is a planning point rather than a technical one, and it argues for choosing the model with the right granularity at the outset.

The wider question of adding capacity later is covered on Modular and Stackable Home Batteries: Expanding Capacity Later, and the capacity figures themselves, including the difference between nominal and usable kWh, are explained on Battery Capacity: Nominal kWh, Usable kWh and Depth of Discharge.

Cost in the UK: unit prices and fully installed kit prices

There is no manufacturer list price for the EP6 or EP12. The figures that exist are distributor listings, and they disagree. The EP12-H is listed at £2,215.19 including VAT and at £2,099.99⁴. The EP6-H is listed at £1,024.99 excluding VAT and at £1,229.99 including VAT⁴. The two EP12 figures and the two EP6 figures are not reconciled in the documents, so both are given here and neither should be treated as the price.

The junction box is priced separately. Distributor listings give the Fox junction box for paralleling up to four EP batteries at £122.95 and at £147.54, and again the two figures disagree⁴. A household budgeting for a two battery stack should expect the junction box as an additional line rather than as part of the battery price.

Installed prices are quoted by the installer after a survey, and the battery is normally sold as part of a full system with an inverter and often solar. For context on what a complete home battery installation costs in the UK, see How Much Does a Home Battery Cost in the UK?. The VAT treatment of the figures above is not stated, so they should be read as quoted rather than as confirmed VAT-inclusive prices.

Availability and what buying an EP battery means for household independence

Fox ESS batteries are sold through installers and distributors rather than direct, and the EP range is one part of a wider product set that includes hybrid inverters, PV inverters and backup equipment²¹. The company reports that it achieved the number one market share in Europe's residential energy storage market, and that it topped global residential ESS shipments in the first half of 2026²². Those are the maker's own announcements.

For a household, an EP battery does three things for independence and leaves three dependencies in place. It stores solar generation for evening use rather than exporting it, which reduces the amount of grid electricity bought. It can support backup during a grid outage where the system includes the right equipment, since the EPS Box SP isolates the property from the grid and restores power using battery and solar after a short transfer delay²⁰. And it allows a household to shift consumption away from peak periods where a time-of-use tariff is in place.

The dependencies are the grid connection itself, the inverter that the battery must be paired with, and the manufacturer's system for monitoring and control. A battery does not make a home independent of the grid; it changes when the home draws from it. The wider picture is set out on Home Batteries and Household Energy Independence.

How the EP range fits Fox ESS's position in the UK and European storage market

Fox ESS develops high-voltage residential battery systems for a range of home energy storage applications, and describes its batteries as scalable, high-performance lithium units for residential solar energy storage⁷. The EP range sits within that portfolio alongside the EQ and CQ ranges, the hybrid inverter families and the backup products.

The company's own announcements place it prominently in the market. Fox ESS reports the number one market share in Europe's residential energy storage market, and states that it topped global residential ESS shipments in the first half of 2026²². It also announced that Infineon supplies silicon carbide technology to Fox ESS to enhance the efficiency of residential energy storage systems²². These are company statements rather than independent assessments.

The EP range is one of several Fox ESS battery families sold in the UK, and the differences between them matter when specifying a system. The EQ range is covered on Fox ESS EQ series batteries, and the wider Fox ESS product set is covered on Fox ESS Home Batteries and Hybrid Systems. The PowerQ modular system has its own page at Fox ESS PowerQ: Modular Home Battery System.

For a household weighing the EP6 against the EP12, the decision comes down to capacity granularity, wall space and the junction box threshold. Both models share the same parallel limit, the same model-mixing rule and the same inverter compatibility, so the choice is about how much storage the house needs and how finely that capacity should be divisible.