FoxStar / Fox ESS Battery Storage in Cornwall

The FoxStar / Fox ESS line-up spans the newer EP5 stackable battery, the established ECS (Energy Cube System) cabinet, and the matching H1/H3 hybrid inverters. The table below shows the configurations CCS most commonly fits in Cornwall, with usable capacity, continuous power, coupling type and typical fitted price.

Prices are fully fitted including 0% VAT, MCS commissioning and DNO notification, and assume an existing or simultaneously-installed solar PV system where relevant. Every FoxStar battery carries a 10-year manufacturer warranty with an 80% capacity-retention guarantee. See the battery storage Cornwall hub for whole-system pricing.

FoxStar (Fox ESS) and the Tesla Powerwall 3 are the two batteries Cornish homeowners ask us to compare most often. Both use safe LFP cell chemistry and carry a 10-year warranty; the differences are cost, scalability and backup depth.

In short: choose FoxStar if you want the best value, modular scaling and three-phase capability for a rural property; choose Tesla Powerwall 3 if seamless whole-home backup during Cornwall's winter storm outages is your priority. CCS fits both and will recommend honestly at survey — compare alongside the Sigenergy SigenStor if you also want integrated EV charging.

Fox ESS's signature feature is the modular ECS battery cabinet. Each cabinet contains a master controller (Mira HV5000) and 2–8 stacked HV2600 battery modules (2.9kWh each). This means you can specify exactly the capacity you need today — say 8.7kWh (3 modules) — and add additional modules later as your needs grow, without replacing the master controller or rewiring the system. Adding a module typically takes a CCS engineer 90 minutes and costs around £1,400 for the module itself plus minimal labour.

This modularity is particularly valuable in Cornwall because energy needs evolve rapidly: today's solar-only customer may add a heat pump in 2 years and an EV in 4 years. Each addition justifies more storage. With a Fox ECS, you scale up incrementally rather than paying for capacity you don't yet need.

Fox ESS supports both AC and DC coupling. For new solar plus storage installations, we typically specify the Fox H1 (single-phase 3.0–6.0kW) or H3 (three-phase 5.0–15.0kW) hybrid inverter, which integrates solar MPPT and battery management in one device — DC-coupled for maximum efficiency (around 97% round-trip). For retrofitting storage to an existing solar PV system, we use the Fox AC1 inverter to AC-couple the ECS battery alongside your existing string inverter — typically achieving 92–93% round-trip efficiency.

The H3 three-phase inverter is particularly relevant for larger rural Cornish properties on three-phase grid supply (common in farms, large country homes, and properties with grid-tied EV charging plus heat pumps). Fox is one of very few brands offering true residential three-phase hybrid inverters at sensible price points. See our battery storage overview.

FoxCloud is Fox ESS's free smartphone and web monitoring platform. Real-time view of solar generation, battery state-of-charge, household consumption, and grid import/export — with historical trending and energy reports. FoxCloud also supports time-of-use scheduling for Octopus Cosy, Flux and Agile tariffs, automatically scheduling battery charge during cheap windows and discharge during expensive periods.

For households on Octopus Flux, the typical Cornish ECS owner achieves additional savings of £400–£700/year purely from tariff arbitrage on top of the solar self-consumption savings. CCS configures FoxCloud and tariff schedules during commissioning, providing a written user guide tailored to your installation.

Cornwall's exposed Atlantic position means winter Atlantic storms regularly cause grid outages — particularly in West Cornwall (TR19, TR20), the Lizard (TR12), and rural North Cornwall (PL30, PL35). The Fox ECS battery, paired with a Fox hybrid inverter, includes built-in EPS (Emergency Power Supply) functionality — when the grid fails, a dedicated EPS output continues powering essential circuits from the battery and any available solar.

EPS is not full whole-home backup like the Tesla Powerwall 3 — it's typically wired to specific essential circuits (fridge/freezer, lighting, broadband router, gas boiler controls) totalling 3–5kW. For Cornish customers wanting full whole-home backup, we recommend either a Tesla Powerwall 3 or a more sophisticated Fox configuration with manual transfer switching. CCS designs EPS arrangements based on your specific resilience needs.

Many rural Cornish properties — farms, larger country homes, properties with multiple outbuildings — are connected to three-phase grid supply. Three-phase is also increasingly common in larger new-build developments. Fox ESS's H3 series hybrid inverter (5kW, 8kW, 10kW, 12kW, 15kW three-phase outputs) is the most cost-effective true three-phase residential hybrid on the UK market today.

For these installations, we typically pair the H3 inverter with a single ECS cabinet (up to 23.3kWh) or paralleled cabinets for larger storage requirements. The whole installation is balanced across the three phases for stable export and import behaviour.

Typical fully installed pricing (May 2026):

• ECS 8.7kWh + H1 5kW hybrid inverter (no PV) — from £6,800
• ECS 8.7kWh + new 5kW solar PV system — from £11,200
• ECS 14.5kWh + new 6kW solar PV system — from £13,800
• ECS 23.3kWh + new 10kW solar PV system — from £17,500
• ECS 14.5kWh + H3 8kW three-phase hybrid (rural) — from £12,400
• Adding an extra HV2600 module to existing system — £1,650 fitted

All prices include 0% VAT, MCS commissioning, DNO G98/G99 notification, and FoxCloud monitoring setup. Modular pricing is a key Fox advantage — no other major brand lets you genuinely scale up incrementally. See our finance options.