Commercial solar battery storage in the UK — the 2026 sizing & cost guide
Batteries used to be the expensive bit. In 2026 LFP cell prices have fallen by more than half since 2022, hybrid inverters ship as standard, and DNOs now handle G99 battery applications routinely. Here's how to size, price and pay back a commercial battery — and when to spend the money on more panels instead.
Short answer
A UK commercial battery in 2026 costs £350–£550 per kWh of usable capacity installed, sized at 30–60% of daily solar generation. Payback is typically 5–8 years on top of solar, or 3–5 years when combined with flexibility revenue. Batteries make sense when you export >30% of your solar or run heavy evening load.
Sizing benchmarks by PV array
| PV size | Battery (usable) | Installed CapEx | Uplift vs solar-only |
|---|---|---|---|
| 100 kWp | 50–100 kWh | £25k–£55k | +£4k–£9k/yr |
| 250 kWp | 150–300 kWh | £70k–£160k | +£11k–£24k/yr |
| 500 kWp | 300–600 kWh | £140k–£320k | +£22k–£48k/yr |
| 1 MWp | 500–1,000 kWh | £230k–£530k | +£40k–£85k/yr |
When a battery earns its keep
- Daytime self-consumption is already above 70% and you're exporting the rest at 4–8p/kWh.
- Your load runs into the evening (bakeries, gyms, hospitality, 2-shift factories).
- You're on a high day/peak import tariff and could shift load out of the 4–7pm peak.
- You want backup for a critical load (cold store, IT room, production line).
- You want to stack revenue by trading into a flexibility platform (Octopus, GridBeyond, Piclo Flex).
LFP vs NMC — what to specify
Specify lithium-iron-phosphate (LFP) for a commercial installation. LFP runs at higher cycle counts (6,000–10,000 vs 3,000–5,000 for NMC), is far more thermally stable, and is now cheaper per kWh. NMC is only worth considering where footprint is tight, which is rarely a constraint on a UK commercial site.
Grid rules — G99 and export limitation
Any battery over 3.68 kW single-phase or 11 kW three-phase needs a G99 application before install. Where the DNO can't accept full export, a G100 export limitation scheme lets you install the battery and cap grid injection at 0 kW or a fixed value. Timescales are typically 4–12 weeks; we run this application in parallel with design.
Flexibility revenue — the stack
A battery over 100 kWh can be enrolled with an aggregator to sell Dynamic Containment, DFR, or wholesale trades. Typical UK revenue is £30–£90 per kWh per year on top of self-consumption savings, split with the aggregator. This is optional and doesn't affect warranty when correctly configured.
Related reading
FAQ
Is commercial solar battery storage worth it in the UK?
Yes when your site has good daytime solar but exports 30%+ of it, or when a large evening load pushes you into peak-tariff import. In those cases a right-sized battery pays back in 5–8 years and typically adds 15–30% to solar-only savings.
How much does commercial battery storage cost per kWh?
In 2026, installed UK commercial battery storage is £400–£550/kWh of usable capacity for 100–500 kWh systems, and £350–£450/kWh at 500 kWh–2 MWh. Includes lithium-iron-phosphate (LFP) cells, hybrid inverter, EMS, install and DNO application.
How big a battery should I install with my solar array?
As a rule of thumb, size the usable battery capacity at 30–60% of daily solar generation on an average summer day. That captures midday surplus without oversizing for winter when there's little to store.
Can commercial batteries provide backup power?
Yes if paired with a hybrid inverter and an automatic transfer switch (ATS). LFP systems can island a critical circuit — cold store, server room, life-safety systems — within milliseconds of a grid outage.
Do I need DNO approval for a commercial battery?
Yes. Batteries connect under G99 (or G100 with export limitation). Application timescales are typically 4–12 weeks; larger sites needing HV works can take longer.
Can a battery earn extra revenue?
Yes. UK commercial batteries can stack Dynamic Frequency Response, capacity market bids, and wholesale trading through aggregators such as Octopus, GridBeyond, and Flexitricity — typically adding £30–£90/kWh/yr on top of self-consumption savings.
Model a battery for your site
The calculator sizes battery and solar together based on your load profile and tariff.