Category: Economics

PPA vs Rooftop Lease: 25-Year Cashflow Compared

Two very different deals: PPA pays you in cheap kWh; rooftop lease pays you in cash. 25-year DCF model for a 500kWp roof.

Last reviewed 13 May 2026 6 min read By Economics

Two very different deals

Rooftop lease: you rent your roof to a generator for £5-15k/MWp/year. PPA: you buy the kWh for 11-16 p. Same roof, totally different outcomes.

25-year DCF model

For a 500kWp roof generating 475,000 kWh/year at 75% self-consumption:

PPARooftop lease
Year-1 cash inflow£0£3,750 (£7.50/MWp/yr × 500 kWp)
Year-1 cash outflow saving£82,000 (vs 30p grid)£0 — you still buy from grid
Year-1 net benefit£82,000£3,750
25-year cumulative (DCF 5%)£1.05m£52k
Best forSites that use kWhRoof-rich, low-power-use

When rooftop lease wins

  • Small electricity user with huge roof (warehousing tenant, lorry park, self-storage)
  • Site sells to a buyer who wouldn't want a PPA
  • Strict no-OpEx constraint
  • Risk-averse — fixed annual rental cleaner than per-kWh variable

When PPA wins

  • Any site that uses 50%+ of the generation
  • Strong daytime load profile
  • Want to reduce Scope 2 emissions
  • Need MEES / ESOS / TCFD evidence
Donovan Fawcett · Director, SEO Dons Ltd Twelve years in UK commercial solar SEO and PPA advisory. Editorial policy & independence.

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