Ready to build vs operational solar assets

A ready to build solar asset is a project that has secured everything it needs to start construction but has not yet been built, while an operational solar asset is a project that has been constructed, energised and is generating electricity. The distinction sits at the heart of how UK solar is traded, because the stage a project has reached determines the risk a buyer takes on, the price the buyer pays and, in most cases, which type of buyer is even interested. Understanding it is the single most useful thing for anyone weighing up a solar acquisition.

We broker both ready to build projects and operational solar farms, along with grid connections, and we sit between sellers and buyers on each. This article sets out what ready to build and operational actually mean, how risk transfers as a project moves through its life, what a buyer is really paying for at each stage, who buys each type, where co-located battery storage fits, and which of the two tends to sell faster and why. Buyers register their mandates with us precisely because their appetite for one stage or the other defines what we should bring to them, so getting the distinction right matters commercially as well as technically.

What does ready to build actually mean for a solar project?

Ready to build, usually shortened to RTB, describes a solar project that has cleared every development hurdle and is ready for construction to begin. In practice that means it holds full planning consent, a signed grid connection agreement, a secured land lease and the other rights and consents needed to build, but no panels have yet been installed. The term marks the point at which the development phase ends and the construction phase can start, which is why it is such a clear milestone in a project's life.

It helps to place RTB against the two milestones that bracket it. Notice to proceed, often written NTP, is the moment the owner formally instructs the contractor to begin construction, which follows shortly after a project reaches ready to build and secures its funding. Commercial operation date, written COD, is the moment the completed project is energised and begins generating and selling electricity. A ready to build project sits before both: fully consented, fully de-risked on planning and grid, but not yet a physical, income-producing asset.

Because a ready to build project has removed the largest development uncertainties, planning refusal and grid rejection, it is far more valuable and far more saleable than an early-stage project still working through those consents. Savills has publicly marketed development rights for ready to build solar projects, which shows that RTB assets are a recognised and traded category in their own right. What the buyer of an RTB project does not yet have is a built asset or any generation revenue, and that gap is the essence of the difference between ready to build and operational.

How does risk transfer as a solar project moves through its stages?

A solar project sheds risk in identifiable steps as it advances, and each step that is cleared is a risk the next owner no longer has to carry. In early development the dominant risks are planning and grid: whether the local authority will grant consent and whether a grid connection can be secured on workable terms. These are binary and can end a project entirely, so a project that has not yet cleared them is speculative and priced accordingly.

At ready to build, those development risks are largely resolved. What remains is construction risk, the possibility that the project costs more or takes longer to build than expected, or encounters ground, weather or contractor problems, plus the market and connection-date risk that revenue depends on. Between notice to proceed and commercial operation, construction risk is being actively worked off as the asset is physically built and tested. By the time a project reaches commercial operation, the buyer's remaining exposures are operational and market ones: how reliably the asset generates, how well it is maintained and what price it earns for its power.

This staged shedding of risk is why the same underlying project commands very different prices at different points. Each milestone cleared, planning, grid, construction, energisation, converts an uncertain future outcome into a known fact, and the buyer who acquires the asset after that milestone pays for the certainty rather than taking the risk of achieving it. A seller therefore captures value by taking a project through a stage, while a buyer chooses which risks it is equipped to take and prices the asset for the risks that remain.

What is a buyer really paying for at each stage?

At the ready to build stage, a buyer is paying for time and optionality. The project has been de-risked on planning and grid, which represents years of development work already completed, so the buyer avoids that time and effort and can move more or less straight to construction. What the buyer is not paying for is income, because there is none yet, so an RTB price reflects the development margin embedded in the consented project rather than any stream of revenue.

At the operational stage, a buyer is paying for certainty and income. The asset is built, energised and generating, so there is a track record of production and a live revenue stream, whether from a power purchase agreement, a Contract for Difference or merchant sales into the wholesale market. The buyer takes on none of the construction risk and steps straight into cash flow, which is why operating assets are priced as income-producing infrastructure and command the fullest prices in the market.

In between, at a project under construction, a buyer is paying for a partly de-risked asset and is sharing the remaining construction risk with the timeline to commercial operation. The way to read the whole spectrum is that price rises as certainty rises: the earlier the stage, the cheaper the entry but the more work and risk the buyer must absorb; the later the stage, the higher the price but the more the buyer is simply buying a finished, income-generating business. Which trade a buyer wants depends entirely on its capability and its appetite for risk.

Who buys ready to build solar and who buys operational assets?

The two stages attract largely different buyers, because they demand different capabilities. Ready to build projects are bought mainly by parties that can construct and operate: independent power producers, utilities, and developers or contractors with the in-house engineering to build the asset out. These buyers are equipped to take construction risk and want to capture the value created by building a consented project, so an RTB asset that still needs constructing fits their mandate well.

Operational assets are bought mainly by parties that want income without construction risk: infrastructure funds, pension funds, institutional investors and dedicated renewable energy funds. For these buyers the attraction is a built, generating asset with a revenue record and long, often inflation-linked cash flows that match long-dated liabilities. They generally have no wish to take construction risk and will pay the fuller price that a de-risked, income-producing asset commands.

There is overlap at the edges. Some large IPPs and funds will take ready to build projects because they have or can hire construction capability, and some developers hold assets through construction and into operation before selling. But the broad pattern holds, and it is why buyers register their mandates with us stating the stage they want. When we know that one buyer builds and another only buys income, we can bring an RTB project to the first and an operating farm to the second, rather than offering either asset to a buyer for whom it is the wrong shape.

Where does co-located battery storage fit into the picture?

Battery energy storage, often co-located with solar on the same site and behind the same grid connection, has become an increasingly common feature of UK projects. Co-location means pairing a battery with the solar array so that the two share the connection and the land, allowing power to be stored when it is plentiful and cheap and exported when it is scarcer and more valuable. For a buyer, a co-located battery changes both the revenue profile and the analysis of the asset.

At the ready to build stage, a co-located battery adds a second workstream to construction and a second set of revenues to model, which can make the project more attractive to a buyer with the capability to build and optimise storage, and less attractive to one that wants a simple solar build. At the operational stage, a working battery adds revenue streams beyond generation, such as trading the difference between low and high prices and providing services to the grid, but it also adds operational complexity and a separate degradation profile to assess.

The practical effect is that co-location widens the range of buyers for whom an asset is relevant, because it appeals to parties chasing flexible revenue as well as those chasing generation, but it narrows the field to buyers who understand storage. When we appraise a co-located project, we treat the solar and the battery as two linked assets sharing one connection, and we match it to buyers whose mandate covers both. It is one more reason the grid connection sits at the centre of a solar transaction, because it is the shared asset that makes co-location possible in the first place.

Which type of solar asset sells faster, and why?

As a general rule, operational solar assets sell more readily than ready to build projects, because the pool of buyers for a de-risked, income-producing asset is larger and deeper than the pool for a project that still needs building. Infrastructure funds and institutional investors form a broad and well-capitalised set of buyers competing for operating assets, and the certainty of an existing revenue stream makes the diligence more straightforward and the value easier to agree.

Ready to build projects sell to a narrower field, the buyers with construction capability and an appetite for build risk, so a seller of an RTB project is matching to fewer counterparties and the process can take longer to find the right one. That said, demand for good RTB projects is genuine and structural, because the UK needs a great deal of new solar built. The Clean Power 2030 Action Plan, published in December 2024, targets 45 to 47 gigawatts of solar, well above current levels, which underpins sustained appetite for consented projects that can be constructed to help close that gap.

The nuance is that speed depends less on the stage in isolation than on how well the asset is matched and prepared. A well-documented ready to build project taken to the small group of genuine builders can complete quickly, while a poorly prepared operational asset with unresolved lease or debt issues can drag. Our job on either type is the same: appraise it honestly, prepare the data room, and introduce it to the specific buyers whose mandate it fits, which is what turns a slow, uncertain sale into a clean one regardless of stage.