There are really only two ways to put solar on a commercial building. You buy the system, or someone else buys it and sells you the electricity. Everything else is a variation on those two themes. The choice between them is less about which is cheaper in the abstract and more about which constraint your organisation is actually trying to work around, and that constraint is usually capital, tax position or appetite for technical responsibility.
What a power purchase agreement actually is
Under a power purchase agreement, a developer or investor finances, installs, owns and maintains the array on your roof or land. You agree to buy the electricity it produces, at a stated price per kilowatt hour, for a term that commonly runs fifteen to twenty five years. You pay nothing up front. You do not own the equipment, and you are not responsible for repairing it.
The contract price is usually set below your current utility rate, often with a fixed annual escalator, so the saving on day one is modest and grows if utility rates rise faster than the escalator. If utility rates stagnate or fall, the saving narrows, and in an unfavourable scenario a late term contract rate can approach or exceed grid prices. That risk is the price of putting up no capital.
What ownership gives you and what it asks
Buying the system means paying the full installed cost, either from capital reserves or through debt, and keeping every kilowatt hour it generates for the life of the asset. Over twenty five years this almost always produces the lowest cost per kilowatt hour, because you are not paying an investor for the use of their money. You also keep the asset on your balance sheet and take on the obligations that come with it.
The obligations are real but manageable. Inverters will need replacement once during the system life. Someone has to notice when production drops and arrange a repair. Insurance needs extending. None of this is onerous for an organisation with a facilities team, and all of it is a genuine burden for one without.
The tax position is often decisive. Accelerated depreciation and investment tax credits are worth a great deal to an entity with taxable income and nothing at all to one without, which is the original reason third party ownership exists. For tax exempt organisations the picture has shifted with the introduction of direct payment mechanisms, and that change has made ownership viable for a class of buyer that was previously pushed toward contracts by default.
Comparing them on the terms that matter
Cost over the full life
Ownership generally wins, sometimes substantially. A power purchase agreement embeds the investor’s required return, and that return has to come from somewhere. The gap narrows when the host cannot use tax benefits, when borrowing costs are high, or when the host would otherwise not have done the project at all.
Cash flow and budget mechanics
Here the contract route often wins decisively, and not merely because it avoids a capital outlay. In many organisations capital budgets and operating budgets are approved by different people on different cycles. A power purchase agreement turns an energy project into a line in the operating budget, which can be the difference between a project that happens and one that circulates as a proposal for three years.
Risk allocation
Under a contract, production risk sits largely with the owner, because you pay for delivered kilowatt hours. If the system underperforms, you buy less and pay less. Under ownership, underperformance is your problem. That is a genuine advantage of the contract structure and one that gets less attention than it deserves.
Flexibility
Ownership is more flexible. A long contract constrains what you can do with the roof, complicates a building sale, and requires the counterparty’s cooperation for changes. Any organisation that might sell or substantially redevelop the site within the term should read the assignment and buyout provisions very carefully before signing.
The contract clauses that decide whether it was a good deal
Three provisions matter more than the headline rate. The first is the escalator, because a rate that rises every year compounds, and a long term with a high escalator can turn an attractive opening price into an unattractive closing one. Model the final year, not the first.
The second is what happens at the end of the term. Options typically include purchasing the system at fair market value, extending the agreement, or having the owner remove the equipment and restore the roof. Each has very different consequences, and a buyout price described only as fair market value is not a price.
The third is roof and building interface. Who coordinates with the roofing warranty, who pays to lift and reinstall the array if the roof needs work during the term, and who carries responsibility for penetrations. These questions are cheap to answer before signing and expensive to argue about in year nine.
Choosing between them
Ownership tends to suit organisations with available capital, taxable income or access to direct payment, a facilities function capable of overseeing equipment, and a long intended tenure in the building. Contracting tends to suit organisations without capital headroom, without the ability to monetise tax benefits, without technical staff, or with a strong preference for transferring performance risk.
Whichever route you take, the underlying production and tariff analysis is identical, and it deserves the same scrutiny in both cases. A contract priced against an inflated production estimate is not a bargain, and the discipline described in our note on how commercial solar payback is actually calculated applies just as much to a proposal where you put up no money. Institutional buyers weighing the two structures will also recognise the budget approval dynamics discussed in our piece on solar for schools and universities, where the split between capital and operating budgets often decides the structure before the economics do.
Frequently asked questions
Which option is cheaper overall?
Ownership usually produces the lower lifetime cost per kilowatt hour, because a power purchase agreement includes the investor’s return. The gap narrows for hosts that cannot use tax benefits or cannot access capital.
What happens when a power purchase agreement ends?
Typically you can buy the system, extend the contract, or have it removed. Establish the mechanism and the valuation method before signing, because a buyout defined only as fair market value leaves the number open.
Who repairs the system under each structure?
Under a contract the owner is responsible for maintenance and repair. Under ownership you are, including the inverter replacement that most systems need once during their service life.
Does a long contract affect selling the building?
It can. The agreement has to be assigned to the buyer or terminated, and both routes need the counterparty’s cooperation. Review the assignment clause early if a sale is plausible.
Is the contract rate guaranteed to stay below grid prices?
No. The saving depends on how utility rates move relative to the contract escalator. Ask to see the comparison modelled with flat utility rates as well as with rising ones.