Commercial solar · Battery + solar
Battery storage sizing for commercial solar (UK)
Battery storage sizing is a function of three inputs: daily surplus generation (what you'd otherwise export), evening peak demand, and the value of flexibility revenue. This page walks through the standard sizing method and typical battery sizes paired with common solar systems.
Battery + solar at a glance
System size
Battery + solar
Panels
Not applicable — battery only
Roof area
Battery footprint: 3–8 m² depending on capacity
Annual generation
Adds 10–25% to solar self-consumption %
Installed cost
£250–£450 per kWh installed (£25k–£45k per 100 kWh)
After Full Expensing
25% corporation tax saving under Full Expensing
Annual saving
£40–£120 per kWh/year (flexibility) + self-consumption uplift
Payback
6–9 years standalone; 5–7 years paired with new solar
Best fit business types
- Retail and hospitality with evening peaks
- Manufacturing sites on Time-of-Use tariffs
- Sites planning EV charging or heat electrification
- Businesses wanting UPS-level resilience
- Any site with 20%+ solar export today
Design and spec notes
- Rule of thumb: 1–2 kWh battery per kWp of solar.
- Match battery capacity to daily surplus, not annual export.
- Consider Balancing Mechanism / DFS revenue for batteries above 250 kWh.
- Lithium-iron-phosphate (LFP) chemistry dominates commercial applications — safer, 6,000+ cycles.
Related reading
FAQ — Battery + solar systems
How big a battery for a 100 kWp solar system?
Typically 100–200 kWh, sized to shift daily surplus (usually 200–400 kWh in summer) into the evening.
Do batteries qualify for Full Expensing?
Yes — battery storage installed with solar qualifies for 100% Full Expensing for UK limited companies.
Free feasibility review
Request your free feasibility review
Share a few details and our team will send a no-obligation review of your site — indicative system size, annual generation, savings and payback. Prefer to explore numbers yourself first? Run the calculator or contact us directly.
- MCS & RECC accredited installer
- Response within one working day
- No cost, no obligation