A resilience install is defined by the critical load, not by the headline capacity. The question is which circuits must ride through an outage and for how long, because that sets both the battery energy and the transfer design. Done well, it is cleaner, quieter and lower-maintenance than a diesel standby generator, and it earns its keep with daily arbitrage and solar self-consumption between the outages it exists to cover.
The engineering centre of gravity is the changeover. Islanding requires anti-islanding protection compliant with G99, an automatic transfer or changeover arrangement designed to BS 7671, and careful separation of the must-run circuit so that only the critical load is carried. UPS-grade, zero-interruption designs (to BS EN 62040) are available where even a brief break is unacceptable.
How we install backup & resilience install (islanding)
Delivery runs: define and schedule the critical load; design the automatic transfer/changeover and anti-islanding protection; separate and re-feed the must-run circuit; install the battery indoors or outdoors as siting dictates; commission the islanding function under a simulated outage; witnessed testing and O&M handover.
What this install includes
- Islanding or UPS-grade design that rides a critical load through grid outages (cold chain, data, process, life-safety)
- Automatic transfer/changeover engineered into the existing distribution, cleaner and quieter than diesel standby
- Stacks daily arbitrage and solar self-consumption between outages
- Critical-load circuit sized and separated during install
Typical backup & resilience install (islanding)
- Power / capacity
- 50 kW / 100 kWh-1 MW / 2 MWh
- Siting
- plant room / external
- Project value
- £80,000-£1.5m
- Payback
- 8 years
What a backup & resilience install (islanding) costs
Expect £80,000-£1.5m for a backup & resilience install (islanding), at a 8-year payback once demand-charge and self-consumption value is modelled from your data. Qualifying plant gets 100% Annual Investment Allowance to £1m and a 50% first-year allowance thereafter; storage is special-rate, not eligible for full expensing, and general commercial premises do not get 0% VAT. See the cost guide, capital allowances and grants and funding.
Fire strategy and standards
Whether the battery sits indoors or outdoors, the fire design follows PAS 63100:2024 principles, BS EN 62619 / BS EN 62933, and insurer and NFCC expectations, with fire detection integrated so the resilience system does not itself become a risk.
Anti-islanding protection compliant with G99; transfer/changeover to BS 7671; BS EN 62040 for UPS-grade designs. Fire detection/suppression integration to insurer and NFCC expectations. BS EN 62933/62619. Careful sizing of the must-run critical-load schedule.
DNO connection and witnessed commissioning
The connection sets the programme on any backup & resilience install (islanding). We lodge the G99 application early, add a G100 export/import limitation where capacity is tight, and prove the metering and CT design so peak-shaving works from day one. Every install ends with a documented, witnessed commissioning and an O&M handover pack. Read our honest view on whether it is worth it.
Backup & Resilience Install (Islanding): at a glance
| Attribute | Typical for this install |
|---|---|
| Power / capacity | 50 kW / 100 kWh-1 MW / 2 MWh |
| Siting | plant room / external |
| Project value | £80,000-£1.5m |
| Simple payback | 8 years |
| Connection | G99 (G100 limitation where constrained) |
Get a free backup & resilience install (islanding) feasibility
Responds within one working day
- 1. Free desk feasibility from your meter data and roof, no obligation.
- 2. Site survey and a fixed-price proposal, itemised in writing.
- 3. Install and aftercare by MCS-certified engineers.
- MCS Certified
- NICEIC
- RECC
- TrustMark
Common questions
What certifications should a commercial battery installer hold?
Look for MCS commercial certification for the storage element, NICEIC or NAPIT electrical registration, demonstrable G99/G100 experience across UK DNOs, and design to BS EN 62619, BS EN/IEC 62933, and PAS 63100:2024. For container and larger installs, CDM 2015 principal-contractor competence and ISO 9001/14001/45001 matter. Ask to see a commissioning pack and a fire risk assessment from a comparable job, that is the real test of an installer versus a broker.
How is half-hourly metering set up for a battery install?
Behind-the-meter control and settlement depend on accurate half-hourly measurement. We design the CT and metering arrangement so the control system sees site import, export, generation, and the battery correctly, and coordinate any meter change with your supplier or meter operator. Getting the measurement design right at install stage is what makes peak-shaving and G100 limitation actually work in service.
What ongoing maintenance does an installed battery need?
A planned O&M regime: remote 24/7 monitoring with automated alerts, periodic electrical inspection, firmware updates, thermal-management and cell-balancing checks via the battery management system, and fire-system checks. Most clients sign a 10-year-plus O&M agreement aligned to the cell warranty. Software-led optimisation of when to charge and discharge is usually included so the system keeps capturing value as tariffs and DUoS bands move.
How long do the batteries last once installed?
Quality LFP commercial cells are typically warranted for around 6,000-10,000 cycles or 10 years to roughly 70% retained capacity, with real-world life often longer. We size with end-of-life capacity in mind so the system still meets its target late in life, and plan augmentation (adding cells) where it makes sense. The warranted cycle count and degradation curve are stated in every proposal.
Can you install storage to support new EV charging?
Yes, and it is often the cheapest way to add chargers. Rapid and ultra-rapid chargers create short, severe demand spikes that can trigger an expensive grid upgrade. A battery buffers those spikes, charging off-peak and from any on-site solar, so more chargers fit on your existing connection. We design the storage, protection, and charging infrastructure together and hold the combined site within its agreed capacity with a G100 scheme.