Solar battery storage for commercial buildings

Solar panels and battery storage installed together, or batteries retrofitted to an existing array. Storage lifts self-consumption from around 30-50% to 70-80% - which is where most of the financial return actually sits. MCS certified, DNO and G99 handled in-house.

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Solar battery storage is a battery system connected to a solar PV array that stores generated electricity instead of exporting it, releasing it when the building needs it. Without storage a commercial building typically self-consumes only 30-50% of what its array generates; with storage that commonly rises to 70-80%. Rossair installs solar and battery together, or retrofits storage to an existing array, across the UK.

For the solar array itself see commercial solar PV systems. For standalone and grid-scale storage without solar, see BESS projects.

70-80%
Self-consumption with storage
£400-700
Per usable kWh installed
6-10k
Cycles at 80% depth of discharge
15-20 yrs
Typical service life, LFP cells

Why storage is where the return is

A commercial solar array generates hardest in the middle of the day. Most buildings do not consume hardest at the same time. The gap between the two is exported to the grid at a fraction of what you pay to import it back later.

Battery storage closes that gap. It also does several things solar alone cannot:

  • Lifts self-consumption from around 30-50% to 70-80% for a typical commercial load profile
  • Shaves peak demand, reducing capacity and DUoS charges as well as unit consumption
  • Shifts generation into evening and early morning operating hours
  • Supports backup power for protected circuits, where specified at design stage
  • Opens flexibility market participation on larger systems

The right size is set by your actual load profile, not by the size of the array. We size against half-hourly consumption data where it exists, rather than a rule of thumb.

Solar panels and battery storage together, or retrofit

Installing both at once is normally cheaper per unit of capacity - one design, one DNO application, one scaffold, one commissioning visit. It also lets us use DC coupling, where the battery shares an inverter with the array and power is converted once rather than twice.

Retrofitting is equally valid, and often better informed. A building with a year of real generation and consumption data can size a battery against evidence instead of estimate. Retrofits are usually AC-coupled, with the battery running its own inverter on the building’s AC side - slightly less efficient, considerably more flexible, and it does not disturb the existing array.

Either route, the grid side is the same: DNO application and G99 protection, handled in-house as part of the installation rather than passed to a third party.

Battery storage installation - what we deliver

Load profile analysis and sizing, electrical and structural design, DNO application and G99 protection, supply and installation, fire strategy and safety design, controls and monitoring integration, testing, commissioning and handover documentation. Long-term maintenance is available under the same contractor that installed it.

Rossair has been delivering UK building services since 1973. The electrical discipline that runs our maintenance contracts runs our storage installations - named technical lead, documented handover, and the same names on site year after year.

At a glance

Solar battery storage - key facts

Costs, cycle life and self-consumption figures below are industry-typical UK ranges for commercial installations. Project-specific figures are set at feasibility.

Service
Solar-coupled battery storage, new-build or PV retrofit
Configurations
AC-coupled and DC-coupled
Typical commercial scale
50 kWh - several MWh
Chemistry
LFP (lithium iron phosphate) standard for commercial
Typical cycle life
6,000-10,000 cycles at 80% depth of discharge
Self-consumption uplift
Commonly 30-50% to 70-80% with storage
Revenue uses
Peak shaving, triad/DUoS avoidance, flexibility markets
Certification
MCS certified; BS 7671; G99 protection
Grid compliance
DNO application and G99 handled in-house
Fire safety
Designed to BS EN 62933 / NFPA 855 principles
Coverage
UK-wide; South Coast base - Hampshire, Surrey, Sussex, Dorset
Telephone
01420 566822
Frequently asked

Questions about solar battery storage

What is solar battery storage?
Solar battery storage is a battery system connected to a solar PV array that stores generated electricity instead of exporting it, then releases it when the building needs it. Without storage, a commercial building typically uses only 30-50% of what its solar array generates and exports the rest at low value. With storage, self-consumption commonly rises to 70-80%, which is where most of the additional financial benefit comes from.
Should we install solar panels and battery storage at the same time?
Installing together is usually cheaper per unit of capacity - one design, one DNO application, one set of scaffolding and one commissioning visit. But it is not required. Batteries can be retrofitted to an existing solar array at any point, and many buildings do exactly that once they have a year of real generation and consumption data to size against. Retrofitting to a well-documented existing array is straightforward; the main variable is whether the existing inverter allows DC coupling or whether an AC-coupled design is needed.
How much does commercial solar battery storage cost in the UK?
Commercial battery storage in the UK broadly runs £400-£700 per usable kWh installed, falling towards the lower end at larger scale. A 200 kWh commercial system is therefore roughly £80,000-£140,000 depending on configuration, switchgear requirements and site constraints. Retrofit projects carry lower civils cost but sometimes higher electrical cost if the existing installation needs reworking. Rossair scopes a project-specific figure at feasibility.
What is the difference between AC-coupled and DC-coupled battery storage?
In a DC-coupled system the battery sits on the same DC circuit as the solar panels and shares an inverter, which is more efficient because power is converted once rather than twice. In an AC-coupled system the battery has its own inverter and connects on the building’s AC side, which is more flexible and is normally the right answer for retrofitting to an existing array. New-build installations often favour DC coupling; retrofits usually end up AC-coupled.
How long does a commercial battery last?
Commercial systems use LFP (lithium iron phosphate) cells, which typically deliver 6,000-10,000 full cycles at 80% depth of discharge. For a building cycling once a day that is comfortably 15-20 years of service, with gradual capacity fade rather than sudden failure. Warranties are normally written as a guaranteed remaining capacity - often 70% - at a stated cycle count or year, so compare warranties on that basis rather than on headline years.
Does battery storage give us backup power in an outage?
Only if it is specified to. A standard grid-tied battery disconnects during a power cut for safety reasons, the same as a grid-tied solar inverter does. Backup requires additional equipment - an islanding-capable inverter and a changeover arrangement that separates protected circuits from the grid. It is entirely achievable but it is a design decision with cost attached, so it needs to be raised at feasibility rather than discovered afterwards.
Can battery storage earn revenue as well as save cost?
Yes. Beyond avoided import cost, commercial batteries can reduce capacity and DUoS charges by discharging across peak network periods, and larger systems can participate in flexibility services. The revenue available depends on system size, connection and how much operational flexibility the site can tolerate. For most commercial buildings the reliable value is still in self-consumption and peak-charge avoidance, with flexibility revenue as upside rather than the basis of the business case.
What about battery fire safety?
Commercial installations use LFP chemistry, which is substantially more thermally stable than the NMC chemistry used in most consumer electronics and electric vehicles. Beyond chemistry, the controls are in the design: location and separation, ventilation, thermal management, fire detection and suppression, and clear firefighter access and isolation points. Systems are designed to BS EN 62933 and NFPA 855 principles, and the fire strategy is agreed with the building’s existing arrangements rather than bolted on.

If we’re not the right fit, we’ll tell you who is

Find out what storage would do for your building

Send us your half-hourly consumption data and your existing array details if you have them, and we will come back with an indicative size, cost and payback.

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