Battery storage
Fox ESS is the battery brand we fit most, and we choose it on value, not on brochure gloss. The commercial pairing we install is the H3 Pro three-phase hybrid inverter (15–30 kW) with ECS4300H high-voltage battery stacks (8.29–29.03 kWh per stack) — modular, outdoor-rated, and covered by a warranty that runs to twelve years on the batteries if it is registered and monitored properly, which is exactly the kind of small print we handle for you.
If you want the one-paragraph honest verdict: Fox ESS is a high-volume Chinese manufacturer (Foxess Co., Ltd, Wuxi) whose kit delivers more storage per pound than the premium German and Korean names, with UK-published warranty terms we can actually hold them to. It is not the most glamorous name on the market. It is the one whose numbers stack up most often when we model a North East business's half-hourly consumption data — which is why it leads our battery storage work.
Manufacturer image · fox-ess.com The inverter
The H3 Pro is the commercial heart of the Fox range: a three-phase hybrid inverter in six power classes from 15 kW to 30 kW, with three MPP trackers (two strings each), a 1,000 V maximum DC input and support for PV arrays up to 60 kWp on the 30 kW model. Maximum efficiency is 97.2% on the 15 and 20 kW units and 97.1% on the larger classes. It is IP65-rated for outdoor installation and operates from −25°C to +60°C.
Three datasheet details matter more to a business than the headline kilowatts. Each unit has two battery inputs at up to 50 A each, so one inverter carries two full battery stacks. Its backup output switches in under 10 milliseconds at the full inverter rating. And it supports parallel operation of up to ten units — how a farm system and a factory system come from the same hardware. The unit weighs 52.5 kg and wall-mounts on a masonry or properly braced steel substrate, which is a survey point we check rather than discover on install day.
By the datasheet
Every figure below is drawn from the Fox ESS H3 Pro and ECS4300H datasheets — the same numbers the sections on this page cite in full.
15–30 kW
H3 Pro output
three-phase hybrid · six power classes
97.2%
Max efficiency
97.1% on the larger classes
up to 60 kWp
PV per inverter
on the 30 kW model
up to 58 kWh
Storage per inverter
two 29.03 kWh stacks
8.29–29.03 kWh
Per battery stack
2–7 modules · 4.14 kWh each
≥6,000 cycles
Battery cycle rating
>95% round-trip efficiency
IP65
Outdoor-rated
−25°C to +60°C (inverter)
12 years
Battery warranty
registered + Fox Cloud monitored
Home and business
Fox ESS is our pick for commercial storage, but the same modular batteries scale down to a house — and the same electricians install either one.
| For your home | For your business | |
|---|---|---|
| Typical setup | A compact battery for self-consumption and backup | H3 Pro inverters with ECS stacks for peak-shaving |
| Where it fits | Houses adding solar and storage | Farms, factories and warehouses |
| System size | A single, smaller ECS stack | Up to ~58 kWh per inverter, parallel to hundreds of kWh |
| Cell chemistry | LiFePO₄ | LiFePO₄ |
| Backup in a power cut | Yes | Yes |
| Who installs it | The same NICEIC contractor | The same NICEIC contractor |
Why it leads our battery work
More usable storage per pound than the premium German and Korean names — on numbers we model against your half-hourly consumption data, not brochure gloss.
The H3 Pro backup (EPS) output switches in under 10 milliseconds at the full inverter rating, so refrigeration or milking plant carries on through a power cut.
Datasheet-rated for parallel operation of up to ten units — a 15 kW farm system and a multi-hundred-kilowatt factory built from the same hardware family.
IP65-rated and rated from −25°C to +60°C — comfortably beyond anything a County Durham winter throws at a barn or yard.
Manufacturer image · fox-ess.com The batteries
The ECS4300H is a modular, floor-standing high-voltage battery using LiFePO₄ (lithium iron phosphate) prismatic cells — the chemistry we prefer for commercial work because it trades a little energy density for a lot of thermal stability. Each module holds 4.14 kWh, and modules stack from two-high to seven-high for 8.29 to 29.03 kWh per stack at 90% usable depth of discharge, above 95% round-trip efficiency and at least 6,000 cycles. It is IP65-rated for indoor or outdoor installation.
Two numbers your installer should volunteer: a full seven-module stack weighs 263.5 kg on a footprint of roughly 570 × 380 mm — a genuine point load we check the floor for — and the pack discharges to −10°C but charge-derates between 0°C and +15°C, so an unheated barn in January charges more slowly than the brochure season suggests.
With two 29.03 kWh stacks per inverter a single H3 Pro carries just over 58 kWh; run inverters in parallel and the same family scales to the hundreds of kilowatt-hours a serious peak-shaving scheme needs. Whatever the size, the export side goes through a G99 application to Northern Powergrid — part of every quote we issue, not an extra.
This is the section worth reading, because Fox's warranty is genuinely good and genuinely conditional, and most installers quote the first half only.
One piece of honest arithmetic on that throughput cap: 14.9 MWh across a 4.14 kWh module is roughly 3,600 full-cycle equivalents. Cycle the battery hard — one full cycle every day — and the performance warranty's throughput limit arrives around year ten, before the 12-year clock does. That is normal across the industry; we point it out because almost nobody else selling these systems does, and because it is exactly the kind of number that should shape how a peak-shaving battery is sized in the first place.
A battery is a 10-to-12-year component in a 25-to-30-year solar system — plan on that, whatever any salesperson's "lifetime" language implies. Fox's own warranty structure says the same thing: the product cover runs to 12 years at best, and the throughput maths above says the working life of a hard-cycled pack sits in the same range. When we model your payback we use those service lives, not fantasy ones — and if the numbers still work, which for daytime-heavy commercial users they usually do, you will know the case is real. If your site would cycle the battery too lightly to justify the capital, we will tell you that instead.
Both halves of the question deserve an answer. It is priced below the premium European names, and it is also a large-scale manufacturer whose UK-market kit carries published, enforceable UK & Ireland warranty policies — 10 years on the H3 Pro inverter and up to 12 on the batteries, with the conditions set out above. We fit it because the value-per-kilowatt-hour is the strongest case we can currently make to a business, not because it is fashionable.
Yes, within design limits: modules stack to seven high (29.03 kWh per stack), each H3 Pro accepts two stacks, and inverters parallel to ten units. The honest caveat is that mixing old and new modules in one stack is governed by Fox’s requirements at the time, so the cleanest expansions add a stack or an inverter rather than a single module to an aged stack — we design first installs with that growth path in mind.
The H3 Pro’s EPS output switches to backup in under 10 milliseconds at up to the inverter’s full rating — enough that most equipment never notices. What stays on depends on how we segregate your essential circuits at design stage, which is electrical contracting rather than solar magic, and is the part a 30-year electrical firm is rather good at.
Also in our range
Commercial solar, battery, EV or any electrical work — no pressure.
