A power purchase agreement (PPA), or electricity power agreement, is a contract between two parties, one which generates electricity (the seller) and one which is looking to purchase electricity (the buyer).

The PPA defines all of the commercial terms for the sale of electricity between the two parties, including when the project will begin commercial operation, schedule for delivery of electricity, penalties for under delivery, payment terms, and termination.

A PPA is the principal agreement that defines the revenue and credit quality of a generating project and is thus a key instrument of project finance. There are many forms of PPA in use today and they vary according to the needs of buyer, seller, and financing counter parties.

Delivery point
The PPA will distinguish where the sale of electricity takes place in relation to the location of the buyer and seller. If the electricity is delivered in a “busbar” sale, the delivery point is located on the high side of the transformer adjacent to the project. In this type of transaction, the buyer is responsible for transmission of the energy from the seller. Otherwise, the PPA will distinguish another delivery point that was contractually agreed on by both parties.[9]

Electricity rates are agreed upon as the basis for a PPA. Prices may be flat, escalate over time, or be negotiated in any other way as long as both parties agree to the negotiation. In a regulated environment, an Electricity Regulator will regulate the price. A PPA will often specify how much energy the supplier is expected to produce each year and any excess energy produced will have a negative impact on the sales rate of electricity that the buyer will be purchasing.[9] This system is intended to provide an incentive for the seller to properly estimate the amount of energy that will be produced in a given period of time.

Billing and payments
The PPA will also describe how invoices are prepared and the time period of response to those invoices. This also includes how to handle late payments and how to deal with invoices that became final after periods of inactivity regarding challenging the invoice. The buyer also has the authority to audit those records produced by the supplier in any circumstance.[9] There is a defined timeline when PPA Provider has to send an invoice to the Generator or vice versa and if that timeline is not met then it has its own consequences, which varies from one PPA Provider to another.

Performance terms
The buyer will typically require the seller to guarantee that the project will meet certain performance standards. Performance guarantees let the buyer plan accordingly when developing new facilities or when trying to meet demand schedules, which also encourages the seller to maintain adequate records. In circumstances where the output from the supplier fails to meet the contractual energy demand by the buyer, the seller is responsible for retributing such costs. Other guarantees may be contractually agreed upon, including availability guarantees and power-curve guarantees. These two types of guarantees are more applicable in regions where the energy harnessed by the renewable technology is more volatile.[9]