Guide · Process
How Does a Solar PPA Work? The Process, Step by Step
Last updated 15 October 2026 · Figures indicative
Short answer: A solar PPA works in seven stages: eligibility check, desktop design, site and structural survey, proposal and contract, DNO grid application (G99 where needed), installation and commissioning, then monthly billing for the kWh you use. Most UK commercial projects take 4–9 months from first contact to generation, mainly driven by DNO timescales.
The 7 stages of a solar PPA
- 01
Eligibility check
1–2 weeks · You and us
Confirm roof area, energy use, tenure and accounts against funder criteria.
- 02
Desktop design
1–3 weeks · Provider
Satellite imagery and your half-hourly data are used to size the system and forecast generation and savings.
- 03
Site and structural survey
2–4 weeks · Provider / installer
Roof condition, structure, electrical board and access are inspected; an asbestos survey if relevant.
- 04
Proposal and contract
2–6 weeks · Provider and you
Final system size, PPA rate, indexation and term. Your solicitor and accountant review the contract.
- 05
DNO grid application
4–16+ weeks · Provider / installer
G98 or G99 application to your Distribution Network Operator. Often the longest stage.
- 06
Installation and commissioning
2–8 weeks · MCS-certified installer
Scaffolding, mounting, panels, inverters and connection, then testing and DNO witness where required.
- 07
Monthly billing
15–25 years · Provider
You are invoiced for the kWh you use, read from the generation meter.
Timescales are typical ranges for UK rooftop projects and vary by DNO region, system size and site.
What you need to provide
- 12 months of half-hourly electricity data — the most important input for sizing.
- Recent electricity bills showing your unit rate and supply capacity.
- Roof drawings or building plans, and the roof's age and condition if known.
- Proof of ownership, or your lease and landlord contact.
- Two to three years of company accounts for the funder's credit check.
How metering and billing work
The provider fits a generation meter between the solar system and your building. Each month it records how many kWh the system produced that you used, and you are invoiced at the PPA rate. Any electricity you still need comes from your normal supplier on a separate bill.
| Line | Quantity | Rate | Amount |
|---|---|---|---|
| Solar electricity used | 22,000 kWh | 12.0p/kWh | £2,640.00 |
| VAT at 20% | £528.00 | ||
| Total due | £3,168.00 | ||
| Equivalent grid cost (for comparison) | 22,000 kWh | 26.0p/kWh | £5,720.00 + VAT |
In winter the solar line will be much smaller, and your grid bill correspondingly larger — savings follow the seasons.
Grid connection: G98, G99 and G100
- G98 covers small systems (up to 16A per phase, about 11kW three-phase). The installer notifies the DNO after connection.
- G99 covers larger systems — almost all commercial PPAs. The DNO must approve the application before connection, and may require network studies or upgrades.
- G100 covers export limitation: if the DNO limits how much you can export, a control device caps export so a larger system can still connect.
For larger industrial sites and off-site structures, see the guide to types of solar PPA.
Who handles maintenance and insurance
The provider is responsible for maintenance, remote monitoring, repairs and insurance of the system for the whole term. You give reasonable site access and tell the provider about any roof works that might affect the panels. Check who pays if panels must be lifted for roof repairs.
What happens at the end of the term
Typically you choose to extend the agreement (often at a lower rate), take ownership of the system (sometimes for a nominal fee), or have the provider remove the panels and make good the roof. Panels usually keep generating for 30+ years, so ownership at term end can be valuable.
Common delays and how to avoid them
- DNO timescales: apply early; ask whether export limitation (G100) would speed things up.
- Missing half-hourly data: request it from your supplier at the start.
- Landlord consent: involve the landlord before the proposal stage.
- Roof condition: survey early; replace or repair before installation, not after.
- Contract review: brief your solicitor and accountant as soon as you receive heads of terms.
For the wider picture — pricing, risks and contract terms — read the complete solar PPA guide.
Related reading: our complete guide to solar power purchase agreements, how private wire and sleeved PPAs differ, grid connections for industrial solar, what businesses pay per kWh and check whether your site is eligible.
How a solar PPA works: FAQs
How long does solar installation take?
On-site installation of a typical 100–500kWp rooftop system usually takes 2–8 weeks, depending on size, roof access and scaffolding. The whole project, from first contact to generation, typically takes 4–9 months, mainly because of DNO grid-connection timescales.
Is there disruption to operations?
Usually very little. Most work happens on the roof, with scaffolding or edge protection around access points. A short planned shutdown — often a few hours — is needed to connect the system to your electrical board, and can be scheduled out of hours.
Do we pay if the panels don't generate?
No. Under a standard solar PPA you pay only for the electricity the system generates and you use, measured by a dedicated generation meter. If the system is offline, you buy from the grid as normal and pay the provider nothing for that period.
Who applies to the DNO?
The provider or its installer normally prepares and submits the grid-connection application (G98 or G99) to your Distribution Network Operator. You may need to sign a letter of authority and provide details of your existing supply.
What data do we need to provide?
Typically 12 months of half-hourly electricity data (your supplier or meter operator can provide it), recent bills, roof drawings or building plans if available, lease details or proof of ownership, and two to three years of company accounts for the funder's credit check.
Sources
- GOV.UK — Greenhouse gas reporting: conversion factors (DESNZ)
- legislation.gov.uk — The Non-Domestic Rating (Plant and Machinery) (Amendment) (England) Regulations 2022, SI 2022/405
- HMRC — Capital allowances: Annual Investment Allowance and first-year allowances
- Energy Networks Association — G98 and G99 connection requirements
- European Commission JRC — PVGIS photovoltaic yield tool
Price ranges for larger systems, running costs, batteries and PPA rates are indicative market ranges from UK installer, funder and market sources; no official series exists above 50kWp.
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