Category: Technical

Adding Battery Storage to a Solar PPA

Battery storage stacks well with PPA — but the contract drafting and revenue stack split are non-trivial. What the typical 2026 structure looks like.

Why batteries pair with PPAs

A bare solar PPA delivers kWh when the sun shines. Most off-takers consume some at peak times. Battery storage time-shifts surplus from midday to peak demand, increasing self-consumption from 60% to 80%+ — directly improving PPA economics.

How the deal is structured

Two main approaches:

• Bundled PPA + battery: single contract from PPA provider; tariff slightly higher to cover battery capex; provider owns battery for term.
• Separate ownership: off-taker owns battery (cash or asset finance) alongside PPA; provider operates only the solar.

Revenue stack with battery

• Solar PPA self-consumption (main saving)
• SEG export at off-peak (when battery full)
• Peak-shifting (avoid TNUoS / BSUoS peak charges)
• Frequency response services to National Grid (specialist)
• Capacity market revenues (Tier-1+ only)

Sizing the battery

Rule of thumb: 0.5-1 hour of system output. For a 500 kWp solar, that's 250-500 kWh of battery — enough to time-shift surplus into the 4-6pm peak.

Watch-outs

• Fire safety / ESS Class IV classification — insurance premium impact
• Cycle life — typical 6,000-10,000 cycles; 15-year useful life
• Round-trip efficiency 85-90% — accounts for ~£3-5k/yr losses on a 500 kWh battery
• DNO consent — some networks restrict export-side battery use