Quick definition
In a power purchase agreement (PPA), a third party owns the solar panels on your roof and sells you the power they produce. In an adjustable-rate PPA, the price you pay per kWh isn't locked in. It's tied to something external, like a utility rate index or a formula written into the contract, so it moves up or down over the term.
This differs from a fixed-rate PPA, where the price per kWh is set at signing and only changes on a schedule you already know.
At a glance: PPA terms typically run 20 to 25 years. An adjustable rate without a cap can move well beyond a fixed-rate PPA's typical 1 to 3% annual escalator.
Why it matters
Most homeowners who sign a PPA do it to avoid the upfront cost of buying a system outright. The tradeoff is that you're now locked into paying for power at whatever rate the contract sets, for two decades or more. With a fixed-rate PPA, you know that number today. With an adjustable-rate PPA, you don't, unless the contract includes a cap or a clear formula.
Say your adjustable-rate PPA ties your per-kWh price to your utility's standard residential rate. If that utility rate rises 6% a year instead of the 2 to 3% a typical fixed-rate escalator assumes, roughly the range California's Public Utilities Commission cites in its own consumer guidance on solar contracts, your PPA payment climbs right along with it. You'd end up paying more for solar power than you originally expected, even though you never see a change in the panels themselves. For the numbers behind Adjustable-rate PPA, the 25-year lifetime savings calculator in our Savings & Payback section walks through the calculation step by step.
This is why reading the actual rate mechanism matters more than the label. Some adjustable-rate PPAs include a ceiling that limits the worst case. Others don't, and the price is genuinely open-ended. NREL's overview of solar consumer protection makes the same point: a contract with no cap and no predictable formula carries real long-term risk that a fixed-rate PPA doesn't.
Where you'll see this
Before signing any PPA, run the numbers with the PPA cost calculator, which projects your total payments over the contract term based on the rate structure you enter.
If you're comparing an adjustable-rate offer against a fixed-rate one, the PPA vs lease comparison tool and the savings comparison: loan vs PPA tool both help you see the total cost difference side by side rather than judging the rate structure in isolation.
This term comes up most in third-party PPA offers, in contract review before signing, and any time a solar quote includes a rate escalator clause you don't fully understand.
Related terms
Frequently asked
Not automatically. It depends entirely on what the rate is tied to and whether there's a cap. A rate tied to a fixed annual escalator you can calculate in advance is very different from one tied to your utility's own rate, which can rise faster than expected.
A fixed-rate PPA locks in the same per-kWh price for the entire contract term, sometimes with one predictable annual step-up. An adjustable-rate PPA ties the price to something external, like a utility rate index, so it can move up or down based on factors outside your control.
Often, yes. Many installers will add a maximum annual increase or an overall price ceiling if you ask, and some contracts include one by default. Always check the contract's escalator language before signing rather than assuming a cap exists.
They're far less common than in the US, since most Canadian provinces don't have the same third-party PPA market. Where solar PPAs do exist in Canada, they tend to follow fixed-rate structures similar to US fixed-rate PPAs.